Tubes in broken spotwelder & other questions

All,
I know almost nothing about tubes(AKA valves). My son bought a
capacitor discharge spotwelder that uses tubes. It doesn't work. Parts
of it do but on the whole it appears that it doesn't charge the caps.
There are three types of tubes in the thing.
3 each OA2WA voltage regulators
2 each 2D21 thyratrons
1 each 5U4GB rectifier
There are also 6 each physically large electrolytic caps that are,
I believe, rated for 450 volts. They are made by Sprague and are
marked 200-450. No uf markings though. Apparently a couple rattle when
shaken-probably not a good sign.
There are two transformers. The first has many taps and the second
is connected through a relay to the bank of caps. The secondary of
this xmfr is the spotwelder output.
As near as I can tell the circuit basically operates like so: The
first xmfr provides 450 volts AC which goes through the 5U4GB tube to
be rectified and then through three OA2WA tubes which are connected
in series. From there the power goes to the cap bank and charges the
caps. And from the caps through a big relay to the output xmfr.
The OA2WA tubes have only two of the pins connected. So power goes
in one pin and then out the other to the next OA2WA tube and so on. It
looks like there is no output from the last tube in the series. So
maybe this is why the caps won't charge.
At least one 2D21 thyratron seems to work because the relay that
connects the cap bank works when the machine is triggered.
I would like to know how to test the tubes without a tube tester.
Maybe this means I will need to make a tester. I also would like to
know how to test the big caps. My meter has a cap test function but it
doesn't seem to work with these big caps. Maybe this is because the
caps are high voltage types. Is it (fairly) safe to attempt charging
the caps with line voltage (120 volts) by first rectifying and then
passing the current through a resistor and then to the caps?
Here is a link to pics my son took of the guts of the spotwelder:
https://goo.gl/photos/LF4JKeGyA4YWiCwv9
Any comments about the spotwelder would be much appreciated.
Thanks,
Eric

 

[pfjw@aol.com]

First, where are you? All the tubes you mention are quite common and not very expensive. I probably have all of them in my rather random connection. The bigger issue are those capacitors.

Please note the interpolations.

On Monday, November 14, 2016 at 1:34:55 PM UTC-5, et...@whidbey.com wrote:

All,
I know almost nothing about tubes(AKA valves). My son bought a
capacitor discharge spotwelder that uses tubes. It doesn't work. Parts
of it do but on the whole it appears that it doesn't charge the caps.
There are three types of tubes in the thing.
3 each OA2WA voltage regulators
2 each 2D21 thyratrons
1 each 5U4GB rectifier
There are also 6 each physically large electrolytic caps that are,
I believe, rated for 450 volts. They are made by Sprague and are
marked 200-450. No uf markings though. Apparently a couple rattle when
shaken-probably not a good sign.

200uF @ 450V. You could pay anywhere from $15 to $100 for those caps. Given the application, do not cheap out, but get as high a quality as you can afford. You also have the choice to put caps in parallel to make the capacity - and series/parallel to make a higher working voltage. There is plenty of room given the size of modern caps to go this route.

There are two transformers. The first has many taps and the second
is connected through a relay to the bank of caps. The secondary of
this xmfr is the spotwelder output.
As near as I can tell the circuit basically operates like so: The
first xmfr provides 450 volts AC which goes through the 5U4GB tube to
be rectified and then through three OA2WA tubes which are connected
in series. From there the power goes to the cap bank and charges the
caps. And from the caps through a big relay to the output xmfr.
The OA2WA tubes have only two of the pins connected. So power goes
in one pin and then out the other to the next OA2WA tube and so on. It
looks like there is no output from the last tube in the series. So
maybe this is why the caps won't charge.

It is probably a blessing that your rectifier (5U4) tube does not work. Were you to be passing B+ - well, the results may be unhappy - see below.

At least one 2D21 thyratron seems to work because the relay that
connects the cap bank works when the machine is triggered.
I would like to know how to test the tubes without a tube tester.

Other than for filament continuity and gross shorts (shorts on a cold tube), no you have no certain way to test tubes without a tester.

Maybe this means I will need to make a tester. I also would like to
know how to test the big caps. My meter has a cap test function but it
doesn't seem to work with these big caps. Maybe this is because the
caps are high voltage types. Is it (fairly) safe to attempt charging
the caps with line voltage (120 volts) by first rectifying and then
passing the current through a resistor and then to the caps?
Here is a link to pics my son took of the guts of the spotwelder:
https://goo.gl/photos/LF4JKeGyA4YWiCwv9
Any comments about the spotwelder would be much appreciated.
Thanks,
Eric

The big caps are toast - full stop. DO NOT EVEN TRY to operate the tester without them as it is possible to do permanent damage to the transformers if the caps are shorted.

If you are anywhere near the Melrose Park section of Cheltenham Township (Philadelphia area) let me know. Despite the size and industrial application, this is a fairly basic issue to troubleshoot.

Now, showing my age, I used one of those ancient beasts some 40 years ago when I was working as a machinist. When set up properly, they are amazingly versatile. I used one to weld various thickness of inconel wave washers and pimple washers onto stainless steel seal backs for aircraft and nuclear applications. From stuff that was almost as thin as paper (0.004 thick) to stuff as thick as index card stock - dial in the machine, pass the pull-tests and it would hold the setting, effectively, until changed. There was a small stash of tubes above the machine - but no 2D21s. When one of them died one way, I found it at Leon Fertik's establishment for $1.50. I replaced them both and purchased two spares. The machine shop is still with us and thriving. Leon, sadly gave up his shop after his wife passed.

Best of luck with it - I can think of a lot of uses.... Especially if your son is an artist.

Peter Wieck
Melrose Park, PA

 

[pfjw@aol.com]

On Monday, November 14, 2016 at 2:48:20 PM UTC-5, et...@whidbey.com wrote:

I'm north of Seattle on Whidbey Island so a visit would be unlikely.
My son has tried to power the thing up and even though parts do work
it won't do any welding. There is no odor of magic smoke so I think
the xmfrs are both OK. I told my son not to power it up any more until
we figure out what's wrong with the thing. The welder has two ranges:
0 to 20 watt seconds and 0 to 200 watt seconds. And my son has uses
for both ranges. Since I sorta talked him into getting a spot welder
like this one I kinda need to make sure we get it up and running.
Thanks for the advice and cap ID.
Eric

Yeah - that is a bit distant, for now. I did get a chance to visit one of the participants herein in his native habitat (central Texas) recently, so, stranger things have happened.

At this point:

a) Focus on the caps. Get them replaced with caps rated, either singly or in combination at 200uF @ 450V minimum. Some basic rules of thumb: Caps in series are additive for capacity, but not for voltage. 10 x 20uF @ 450V (IN PARALLEL) = 200uF @ 450V.

Two caps in series must be calculated, but keeping it very simple, if two 20uF @ 450V are connected in series, the actual capacitance will be 5uF @ 900V. You may see the calculations here: https://www.kitronik.co.uk/blog/how-to-calculate-capacitors-in-series-and-parallel/

b) Test the tubes by checking the filaments and for any dead shorts internally when cold. A base diagram will tell you which are the filament pins, and then any pin to any pin not internally connected (also given on the base diagram) for shorts.

There are lots of sources for tubes - if you get stuck, let me know and I will root through my spares box. I have 0A2s and 5U4s, most likely in some quantity. As to 2D21s I am not sure, but they are stocked at Antique Electronics Supply (AES) for $5 or so.

Then, your best friend is cleaning anything that can be cleaned without damage. Dust removal, correct lubrication if applicable, rust removal (Beware of steel wool!) and similar.

Best of luck with it - given that you are in the PNW, and, worse, on an island, make sure that you keep the system dry and free of salt. Given the operating parameters of that beast - you DO NOT want stray currents floating around.

Peter Wieck
Melrose Park, PA

 

[pfjw@aol.com]

Forgive the top posting but WARNING: if a big honking electrolytic capacitor that is more than 60 years old is rattling when shaken, it is absolutely and irredeemingly, irrevocably TOAST. As are its siblings. Reforming is an exercise in futility, and possibly very dangerous, as if by some chance you do actually reform one (or more) for the moment, and it should fail under actual use, all the work previous would be for naught. **POW**.

Agree on the photoflash caps in any case. However, I suspect that the OEM caps are vastly oversize to make up for their rather slow chemistry.

Peter Wieck
Melrose Park, PA

On Monday, November 14, 2016 at 2:57:48 PM UTC-5, John Robertson wrote:

On 201611/14/ 11:12 AM, pfjw@aol.com wrote:
First, where are you? All the tubes you mention are quite common and not very expensive. I probably have all of them in my rather random connection. The bigger issue are those capacitors.

Please note the interpolations.

On Monday, November 14, 2016 at 1:34:55 PM UTC-5, et...@whidbey.com wrote:
All,
I know almost nothing about tubes(AKA valves). My son bought a
capacitor discharge spotwelder that uses tubes. It doesn't work. Parts
of it do but on the whole it appears that it doesn't charge the caps.
There are three types of tubes in the thing.
3 each OA2WA voltage regulators
2 each 2D21 thyratrons
1 each 5U4GB rectifier
There are also 6 each physically large electrolytic caps that are,
I believe, rated for 450 volts. They are made by Sprague and are
marked 200-450. No uf markings though. Apparently a couple rattle when
shaken-probably not a good sign.

200uF @ 450V. You could pay anywhere from $15 to $100 for those caps. Given the application, do not cheap out, but get as high a quality as you can afford. You also have the choice to put caps in parallel to make the capacity - and series/parallel to make a higher working voltage. There is plenty of room given the size of modern caps to go this route.


There are two transformers. The first has many taps and the second
is connected through a relay to the bank of caps. The secondary of
this xmfr is the spotwelder output.
As near as I can tell the circuit basically operates like so: The
first xmfr provides 450 volts AC which goes through the 5U4GB tube to
be rectified and then through three OA2WA tubes which are connected
in series. From there the power goes to the cap bank and charges the
caps. And from the caps through a big relay to the output xmfr.
The OA2WA tubes have only two of the pins connected. So power goes
in one pin and then out the other to the next OA2WA tube and so on. It
looks like there is no output from the last tube in the series. So
maybe this is why the caps won't charge.


I suggest you consider PHOTOFLASH rated caps - they have a very fast
discharge (low internal ESR - you might want to get a Blue ESR meter to
test these caps) and aren't too expensive...

http://ca.mouser.com/Passive-Components/Capacitors/_/N-5g7r?Keyword=photoflash&FS=True

Look up REFORMING capacitors. Even old ones like yours may be saved,
there was a recent thesis published that showed how large value caps can
last a long time if they are reformed carefully.

2D21's are very old design - there are many circuits online to replace
them with SCRs if you want to bring the machine up to the 21st century...

Likewise your 5U4s, this can be replaced with a solid state bridge (dual
diode) rectifier. As the 5U4 has its own transformer then you need to
make sure it is fused correctly on the primary side in case of a shorted
diode.

OA2 tubes are 150VDC regulators, so with three of them the output is
regulated to 450VDC. If the OA2s are glowing purple then they are at
their regulated voltage (more or less) - all three need to be glowing
for your 450VDC to be regulated. I would expect them to be across the
output of the 5U4 to ground to regulate the output voltage...

John :-#)#


It is probably a blessing that your rectifier (5U4) tube does not work. Were you to be passing B+ - well, the results may be unhappy - see below.

At least one 2D21 thyratron seems to work because the relay that
connects the cap bank works when the machine is triggered.
I would like to know how to test the tubes without a tube tester.

Other than for filament continuity and gross shorts (shorts on a cold tube), no you have no certain way to test tubes without a tester.

Maybe this means I will need to make a tester. I also would like to
know how to test the big caps. My meter has a cap test function but it
doesn't seem to work with these big caps. Maybe this is because the
caps are high voltage types. Is it (fairly) safe to attempt charging
the caps with line voltage (120 volts) by first rectifying and then
passing the current through a resistor and then to the caps?
Here is a link to pics my son took of the guts of the spotwelder:
https://goo.gl/photos/LF4JKeGyA4YWiCwv9
Any comments about the spotwelder would be much appreciated.
Thanks,
Eric

The big caps are toast - full stop. DO NOT EVEN TRY to operate the tester without them as it is possible to do permanent damage to the transformers if the caps are shorted.

If you are anywhere near the Melrose Park section of Cheltenham Township (Philadelphia area) let me know. Despite the size and industrial application, this is a fairly basic issue to troubleshoot.

Now, showing my age, I used one of those ancient beasts some 40 years ago when I was working as a machinist. When set up properly, they are amazingly versatile. I used one to weld various thickness of inconel wave washers and pimple washers onto stainless steel seal backs for aircraft and nuclear applications. From stuff that was almost as thin as paper (0.004 thick) to stuff as thick as index card stock - dial in the machine, pass the pull-tests and it would hold the setting, effectively, until changed. There was a small stash of tubes above the machine - but no 2D21s. When one of them died one way, I found it at Leon Fertik's establishment for $1.50. I replaced them both and purchased two spares. The machine shop is still with us and thriving. Leon, sadly gave up his shop after his wife passed.

Best of luck with it - I can think of a lot of uses.... Especially if your son is an artist.

Peter Wieck
Melrose Park, PA



--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[pfjw@aol.com]

On Monday, November 14, 2016 at 3:36:25 PM UTC-5, John Robertson wrote:

On 201611/14/ 12:20 PM, pfjw@aol.com wrote:
Forgive the top posting but WARNING: if a big honking electrolytic capacitor that is more than 60 years old is rattling when shaken, it is absolutely and irredeemingly, irrevocably TOAST. As are its siblings. Reforming is an exercise in futility, and possibly very dangerous, as if by some chance you do actually reform one (or more) for the moment, and it should fail under actual use, all the work previous would be for naught. **POW**.

Agree on the photoflash caps in any case. However, I suspect that the OEM caps are vastly oversize to make up for their rather slow chemistry.

Peter Wieck
Melrose Park, PA

I hear what you are saying Peter, but those caps are industrial grade
caps, not what you would find in a radio. Agreed the shake test will
tell if they are really bad (no rattles!), however attempting to reform
them is not an exercise in futility unless there are obvious signs of
venting around the rubber plug on the top of the can.

If you have access to an ESR meter that will give you a pretty good idea
of the capacitors condition. We sell the Bob Parker kit (as do others)
and using that with an ohmmeter to see if the low ESR is an actual short
circuit or not will give you a pretty good idea of the condition of
these electrolytic caps.

These would have been photoflash rated caps originally and they were
common in photographic gear from the 50s and on. My dad's architectural
photography studio had many flash boxes that used racks of those caps,
back in the 50s/60s and 70s.

John :-#)#

PS, I forgive the top-posting (ducking)

I keep "that" ESR meter, and it is extremely useful. I also have a neat little cap tester that actually tests caps at full operating voltage (up to 450V, that is). It is quite interesting to see caps that seem to test OK in the short term, but over time start to get *warmer* and *warmer* until that **POW** actually happens. It may take an hour or two... When I find one of these, I will hang it (connected) in a Home Depot bucket outside and wait ;-)>

My point is that a capacitor, even half-a-dozen capacitors are usually pretty cheap if measured against the alternative failing at a critical moment. These are not the typical cap found in the typical radio - there is a LOT of energy stuffed inside those beasts. Too many for me to trust a 50+ year old cage for containment.

Peter Wieck
Melrose Park, PA

 

>"Two caps in series must be calculated, but keeping it very >simple, if two 20uF @ 450V are connected in series, the >actual capacitance will be 5uF @ 900V. "

That's not what I "heard". It should be 10 uF.

 

[pfjw@aol.com]

On Monday, November 14, 2016 at 4:13:07 PM UTC-5, jurb...@gmail.com wrote:

"Two caps in series must be calculated, but keeping it very >simple, if two 20uF @ 450V are connected in series, the >actual capacitance will be 5uF @ 900V. "

That's not what I "heard". It should be 10 uF.

(C1 x C2) / (C1 + C2) = Working Capacitance is the equation I have used these many years.

Example 1:

10 x 10 = 100
10 + 10 = 20
100 / 20 = 5

Example 2 (from the link):

10 x 22 = 220
10 + 22 = 32
220 / 32 = 6.875

At least where I come from.

Peter Wieck
Melrose Park, PA

 

[pfjw@aol.com]

On Monday, November 14, 2016 at 4:46:42 PM UTC-5, Ralph Mowery wrote:

In article <6fc1c49e-9ee2-4471-8eaf-7746c5246c9c@googlegroups.com>,
pfjw@aol.com says...

On Monday, November 14, 2016 at 4:13:07 PM UTC-5, jurb...@gmail.com wrote:
"Two caps in series must be calculated, but keeping it very >simple, if two 20uF @ 450V are connected in series, the >actual capacitance will be 5uF @ 900V. "

That's not what I "heard". It should be 10 uF.

(C1 x C2) / (C1 + C2) = Working Capacitance is the equation I have used these many years.

Example 1:

10 x 10 = 100
10 + 10 = 20
100 / 20 = 5

Example 2 (from the link):

10 x 22 = 220
10 + 22 = 32
220 / 32 = 6.875

At least where I come from.

Peter Wieck
Melrose Park, PA


If equal value capacitors are in series (same for resistors in parallel)
all you have to do is devide the value of one of them by the number.
That would be 20 devided by 2 for 10.

You can also take the long hard way and do the product over the sum as
in your example. You just need to LOOK AT THE VALUE IN THE EXAMPLE AS
BEING 20 INSTEAD OF THE 10 FOR EACH ONE THAT YOU USED.

For equal values of capacitance the voltage will add, if the voltages
are not equal then there are problems. Resistors are needed across the
capacitors when equal values of capacitors are used. This is mainly due
to the wide variation of capacitance in most of them. Helps to bleed
off the stored charge also.

OK - I have enough stray caps at home to do a lash-up and I have enough very accurate meters to test the actual results of that lash-up. But, I just rebuilt the power-supply of my Dynaco ST-70 and my actual working results were as the equation implied, as I remember.

Nor would I ever run caps of differing voltage in series. Or parallel for that matter.

I will report my results.

Again, here is the link. I am NOT making this up.

https://www.kitronik.co.uk/blog/how-to-calculate-capacitors-in-series-and-parallel/

Peter Wieck
Melrose Park, PA

 

On Mon, 14 Nov 2016 11:12:07 -0800 (PST), "pfjw@aol.com"
<pfjw@aol.com> wrote:

First, where are you? All the tubes you mention are quite common and not very expensive. I probably have all of them in my rather random connection. The bigger issue are those capacitors.

Please note the interpolations.

On Monday, November 14, 2016 at 1:34:55 PM UTC-5, et...@whidbey.com wrote:
All,
I know almost nothing about tubes(AKA valves). My son bought a
capacitor discharge spotwelder that uses tubes. It doesn't work. Parts
of it do but on the whole it appears that it doesn't charge the caps.
There are three types of tubes in the thing.
3 each OA2WA voltage regulators
2 each 2D21 thyratrons
1 each 5U4GB rectifier
There are also 6 each physically large electrolytic caps that are,
I believe, rated for 450 volts. They are made by Sprague and are
marked 200-450. No uf markings though. Apparently a couple rattle when
shaken-probably not a good sign.

200uF @ 450V. You could pay anywhere from $15 to $100 for those caps. Given the application, do not cheap out, but get as high a quality as you can afford. You also have the choice to put caps in parallel to make the capacity - and series/parallel to make a higher working voltage. There is plenty of room given the size of modern caps to go this route.

There are two transformers. The first has many taps and the second
is connected through a relay to the bank of caps. The secondary of
this xmfr is the spotwelder output.
As near as I can tell the circuit basically operates like so: The
first xmfr provides 450 volts AC which goes through the 5U4GB tube to
be rectified and then through three OA2WA tubes which are connected
in series. From there the power goes to the cap bank and charges the
caps. And from the caps through a big relay to the output xmfr.
The OA2WA tubes have only two of the pins connected. So power goes
in one pin and then out the other to the next OA2WA tube and so on. It
looks like there is no output from the last tube in the series. So
maybe this is why the caps won't charge.

It is probably a blessing that your rectifier (5U4) tube does not work. Were you to be passing B+ - well, the results may be unhappy - see below.

At least one 2D21 thyratron seems to work because the relay that
connects the cap bank works when the machine is triggered.
I would like to know how to test the tubes without a tube tester.

Other than for filament continuity and gross shorts (shorts on a cold tube), no you have no certain way to test tubes without a tester.

Maybe this means I will need to make a tester. I also would like to
know how to test the big caps. My meter has a cap test function but it
doesn't seem to work with these big caps. Maybe this is because the
caps are high voltage types. Is it (fairly) safe to attempt charging
the caps with line voltage (120 volts) by first rectifying and then
passing the current through a resistor and then to the caps?
Here is a link to pics my son took of the guts of the spotwelder:
https://goo.gl/photos/LF4JKeGyA4YWiCwv9
Any comments about the spotwelder would be much appreciated.
Thanks,
Eric

The big caps are toast - full stop. DO NOT EVEN TRY to operate the tester without them as it is possible to do permanent damage to the transformers if the caps are shorted.

If you are anywhere near the Melrose Park section of Cheltenham Township (Philadelphia area) let me know. Despite the size and industrial application, this is a fairly basic issue to troubleshoot.

Now, showing my age, I used one of those ancient beasts some 40 years ago when I was working as a machinist. When set up properly, they are amazingly versatile. I used one to weld various thickness of inconel wave washers and pimple washers onto stainless steel seal backs for aircraft and nuclear applications. From stuff that was almost as thin as paper (0.004 thick) to stuff as thick as index card stock - dial in the machine, pass the pull-tests and it would hold the setting, effectively, until changed. There was a small stash of tubes above the machine - but no 2D21s. When one of them died one way, I found it at Leon Fertik's establishment for $1.50. I replaced them both and purchased two spares. The machine shop is still with us and thriving. Leon, sadly gave up his shop after his wife passed.

Best of luck with it - I can think of a lot of uses.... Especially if your son is an artist.

Peter Wieck
Melrose Park, PA

I'm north of Seattle on Whidbey Island so a visit would be unlikely.
My son has tried to power the thing up and even though parts do work
it won't do any welding. There is no odor of magic smoke so I think
the xmfrs are both OK. I told my son not to power it up any more until
we figure out what's wrong with the thing. The welder has two ranges:
0 to 20 watt seconds and 0 to 200 watt seconds. And my son has uses
for both ranges. Since I sorta talked him into getting a spot welder
like this one I kinda need to make sure we get it up and running.
Thanks for the advice and cap ID.
Eric

 

[John Robertson]

On 201611/14/ 11:12 AM, pfjw@aol.com wrote:

First, where are you? All the tubes you mention are quite common and not very expensive. I probably have all of them in my rather random connection. The bigger issue are those capacitors.

Please note the interpolations.

On Monday, November 14, 2016 at 1:34:55 PM UTC-5, et...@whidbey.com wrote:
All,
I know almost nothing about tubes(AKA valves). My son bought a
capacitor discharge spotwelder that uses tubes. It doesn't work. Parts
of it do but on the whole it appears that it doesn't charge the caps.
There are three types of tubes in the thing.
3 each OA2WA voltage regulators
2 each 2D21 thyratrons
1 each 5U4GB rectifier
There are also 6 each physically large electrolytic caps that are,
I believe, rated for 450 volts. They are made by Sprague and are
marked 200-450. No uf markings though. Apparently a couple rattle when
shaken-probably not a good sign.

200uF @ 450V. You could pay anywhere from $15 to $100 for those caps. Given the application, do not cheap out, but get as high a quality as you can afford. You also have the choice to put caps in parallel to make the capacity - and series/parallel to make a higher working voltage. There is plenty of room given the size of modern caps to go this route.


There are two transformers. The first has many taps and the second
is connected through a relay to the bank of caps. The secondary of
this xmfr is the spotwelder output.
As near as I can tell the circuit basically operates like so: The
first xmfr provides 450 volts AC which goes through the 5U4GB tube to
be rectified and then through three OA2WA tubes which are connected
in series. From there the power goes to the cap bank and charges the
caps. And from the caps through a big relay to the output xmfr.
The OA2WA tubes have only two of the pins connected. So power goes
in one pin and then out the other to the next OA2WA tube and so on. It
looks like there is no output from the last tube in the series. So
maybe this is why the caps won't charge.

I suggest you consider PHOTOFLASH rated caps - they have a very fast
discharge (low internal ESR - you might want to get a Blue ESR meter to
test these caps) and aren't too expensive...

http://ca.mouser.com/Passive-Components/Capacitors/_/N-5g7r?Keyword=photoflash&FS=True

Look up REFORMING capacitors. Even old ones like yours may be saved,
there was a recent thesis published that showed how large value caps can
last a long time if they are reformed carefully.

2D21's are very old design - there are many circuits online to replace
them with SCRs if you want to bring the machine up to the 21st century...

Likewise your 5U4s, this can be replaced with a solid state bridge (dual
diode) rectifier. As the 5U4 has its own transformer then you need to
make sure it is fused correctly on the primary side in case of a shorted
diode.

OA2 tubes are 150VDC regulators, so with three of them the output is
regulated to 450VDC. If the OA2s are glowing purple then they are at
their regulated voltage (more or less) - all three need to be glowing
for your 450VDC to be regulated. I would expect them to be across the
output of the 5U4 to ground to regulate the output voltage...

John :-#)#

It is probably a blessing that your rectifier (5U4) tube does not work. Were you to be passing B+ - well, the results may be unhappy - see below.

At least one 2D21 thyratron seems to work because the relay that
connects the cap bank works when the machine is triggered.
I would like to know how to test the tubes without a tube tester.

Other than for filament continuity and gross shorts (shorts on a cold tube), no you have no certain way to test tubes without a tester.

Maybe this means I will need to make a tester. I also would like to
know how to test the big caps. My meter has a cap test function but it
doesn't seem to work with these big caps. Maybe this is because the
caps are high voltage types. Is it (fairly) safe to attempt charging
the caps with line voltage (120 volts) by first rectifying and then
passing the current through a resistor and then to the caps?
Here is a link to pics my son took of the guts of the spotwelder:
https://goo.gl/photos/LF4JKeGyA4YWiCwv9
Any comments about the spotwelder would be much appreciated.
Thanks,
Eric

The big caps are toast - full stop. DO NOT EVEN TRY to operate the tester without them as it is possible to do permanent damage to the transformers if the caps are shorted.

If you are anywhere near the Melrose Park section of Cheltenham Township (Philadelphia area) let me know. Despite the size and industrial application, this is a fairly basic issue to troubleshoot.

Now, showing my age, I used one of those ancient beasts some 40 years ago when I was working as a machinist. When set up properly, they are amazingly versatile. I used one to weld various thickness of inconel wave washers and pimple washers onto stainless steel seal backs for aircraft and nuclear applications. From stuff that was almost as thin as paper (0.004 thick) to stuff as thick as index card stock - dial in the machine, pass the pull-tests and it would hold the setting, effectively, until changed. There was a small stash of tubes above the machine - but no 2D21s. When one of them died one way, I found it at Leon Fertik's establishment for $1.50. I replaced them both and purchased two spares. The machine shop is still with us and thriving. Leon, sadly gave up his shop after his wife passed.

Best of luck with it - I can think of a lot of uses.... Especially if your son is an artist.

Peter Wieck
Melrose Park, PA

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[John Robertson]

On 201611/14/ 12:20 PM, pfjw@aol.com wrote:

Forgive the top posting but WARNING: if a big honking electrolytic capacitor that is more than 60 years old is rattling when shaken, it is absolutely and irredeemingly, irrevocably TOAST. As are its siblings. Reforming is an exercise in futility, and possibly very dangerous, as if by some chance you do actually reform one (or more) for the moment, and it should fail under actual use, all the work previous would be for naught. **POW**.

Agree on the photoflash caps in any case. However, I suspect that the OEM caps are vastly oversize to make up for their rather slow chemistry.

Peter Wieck
Melrose Park, PA

I hear what you are saying Peter, but those caps are industrial grade
caps, not what you would find in a radio. Agreed the shake test will
tell if they are really bad (no rattles!), however attempting to reform
them is not an exercise in futility unless there are obvious signs of
venting around the rubber plug on the top of the can.

If you have access to an ESR meter that will give you a pretty good idea
of the capacitors condition. We sell the Bob Parker kit (as do others)
and using that with an ohmmeter to see if the low ESR is an actual short
circuit or not will give you a pretty good idea of the condition of
these electrolytic caps.

These would have been photoflash rated caps originally and they were
common in photographic gear from the 50s and on. My dad's architectural
photography studio had many flash boxes that used racks of those caps,
back in the 50s/60s and 70s.

John :-#)#

PS, I forgive the top-posting (ducking)

On Monday, November 14, 2016 at 2:57:48 PM UTC-5, John Robertson wrote:
On 201611/14/ 11:12 AM, pfjw@aol.com wrote:
First, where are you? All the tubes you mention are quite common and not very expensive. I probably have all of them in my rather random connection. The bigger issue are those capacitors.

Please note the interpolations.

On Monday, November 14, 2016 at 1:34:55 PM UTC-5, et...@whidbey.com wrote:
All,
I know almost nothing about tubes(AKA valves). My son bought a
capacitor discharge spotwelder that uses tubes. It doesn't work. Parts
of it do but on the whole it appears that it doesn't charge the caps.
There are three types of tubes in the thing.
3 each OA2WA voltage regulators
2 each 2D21 thyratrons
1 each 5U4GB rectifier
There are also 6 each physically large electrolytic caps that are,
I believe, rated for 450 volts. They are made by Sprague and are
marked 200-450. No uf markings though. Apparently a couple rattle when
shaken-probably not a good sign.

200uF @ 450V. You could pay anywhere from $15 to $100 for those caps. Given the application, do not cheap out, but get as high a quality as you can afford. You also have the choice to put caps in parallel to make the capacity - and series/parallel to make a higher working voltage. There is plenty of room given the size of modern caps to go this route.


There are two transformers. The first has many taps and the second
is connected through a relay to the bank of caps. The secondary of
this xmfr is the spotwelder output.
As near as I can tell the circuit basically operates like so: The
first xmfr provides 450 volts AC which goes through the 5U4GB tube to
be rectified and then through three OA2WA tubes which are connected
in series. From there the power goes to the cap bank and charges the
caps. And from the caps through a big relay to the output xmfr.
The OA2WA tubes have only two of the pins connected. So power goes
in one pin and then out the other to the next OA2WA tube and so on. It
looks like there is no output from the last tube in the series. So
maybe this is why the caps won't charge.


I suggest you consider PHOTOFLASH rated caps - they have a very fast
discharge (low internal ESR - you might want to get a Blue ESR meter to
test these caps) and aren't too expensive...

http://ca.mouser.com/Passive-Components/Capacitors/_/N-5g7r?Keyword=photoflash&FS=True

Look up REFORMING capacitors. Even old ones like yours may be saved,
there was a recent thesis published that showed how large value caps can
last a long time if they are reformed carefully.

2D21's are very old design - there are many circuits online to replace
them with SCRs if you want to bring the machine up to the 21st century...

Likewise your 5U4s, this can be replaced with a solid state bridge (dual
diode) rectifier. As the 5U4 has its own transformer then you need to
make sure it is fused correctly on the primary side in case of a shorted
diode.

OA2 tubes are 150VDC regulators, so with three of them the output is
regulated to 450VDC. If the OA2s are glowing purple then they are at
their regulated voltage (more or less) - all three need to be glowing
for your 450VDC to be regulated. I would expect them to be across the
output of the 5U4 to ground to regulate the output voltage...

John :-#)#


It is probably a blessing that your rectifier (5U4) tube does not work. Were you to be passing B+ - well, the results may be unhappy - see below.

At least one 2D21 thyratron seems to work because the relay that
connects the cap bank works when the machine is triggered.
I would like to know how to test the tubes without a tube tester.

Other than for filament continuity and gross shorts (shorts on a cold tube), no you have no certain way to test tubes without a tester.

Maybe this means I will need to make a tester. I also would like to
know how to test the big caps. My meter has a cap test function but it
doesn't seem to work with these big caps. Maybe this is because the
caps are high voltage types. Is it (fairly) safe to attempt charging
the caps with line voltage (120 volts) by first rectifying and then
passing the current through a resistor and then to the caps?
Here is a link to pics my son took of the guts of the spotwelder:
https://goo.gl/photos/LF4JKeGyA4YWiCwv9
Any comments about the spotwelder would be much appreciated.
Thanks,
Eric

The big caps are toast - full stop. DO NOT EVEN TRY to operate the tester without them as it is possible to do permanent damage to the transformers if the caps are shorted.

If you are anywhere near the Melrose Park section of Cheltenham Township (Philadelphia area) let me know. Despite the size and industrial application, this is a fairly basic issue to troubleshoot.

Now, showing my age, I used one of those ancient beasts some 40 years ago when I was working as a machinist. When set up properly, they are amazingly versatile. I used one to weld various thickness of inconel wave washers and pimple washers onto stainless steel seal backs for aircraft and nuclear applications. From stuff that was almost as thin as paper (0.004 thick) to stuff as thick as index card stock - dial in the machine, pass the pull-tests and it would hold the setting, effectively, until changed. There was a small stash of tubes above the machine - but no 2D21s. When one of them died one way, I found it at Leon Fertik's establishment for $1.50. I replaced them both and purchased two spares. The machine shop is still with us and thriving. Leon, sadly gave up his shop after his wife passed.

Best of luck with it - I can think of a lot of uses.... Especially if your son is an artist.

Peter Wieck
Melrose Park, PA



--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[whit3rd]

On Monday, November 14, 2016 at 2:44:55 PM UTC-8, et...@whidbey.com wrote:

I found 220 mfd 450 caps at JustRadio.com. I'm not sure if these will
discharge fast enough.

For a welding purpose, 100l milliseconds is very fast (no functioning
capacitor you are likely to find would have too high ESR for this job).

ESR gets to be important with low voltage high current, where a fraction of
a volt of ripple is a malfunction. Fraction of a volt difference on a 450V capacitor
charge is negligible.

 

[Ralph Mowery]

In article <6fc1c49e-9ee2-4471-8eaf-7746c5246c9c@googlegroups.com>,
pfjw@aol.com says...

On Monday, November 14, 2016 at 4:13:07 PM UTC-5, jurb...@gmail.com wrote:
"Two caps in series must be calculated, but keeping it very >simple, if two 20uF @ 450V are connected in series, the >actual capacitance will be 5uF @ 900V. "

That's not what I "heard". It should be 10 uF.

(C1 x C2) / (C1 + C2) = Working Capacitance is the equation I have used these many years.

Example 1:

10 x 10 = 100
10 + 10 = 20
100 / 20 = 5

Example 2 (from the link):

10 x 22 = 220
10 + 22 = 32
220 / 32 = 6.875

At least where I come from.

Peter Wieck
Melrose Park, PA

If equal value capacitors are in series (same for resistors in parallel)
all you have to do is devide the value of one of them by the number.
That would be 20 devided by 2 for 10.

You can also take the long hard way and do the product over the sum as
in your example. You just need to LOOK AT THE VALUE IN THE EXAMPLE AS
BEING 20 INSTEAD OF THE 10 FOR EACH ONE THAT YOU USED.

For equal values of capacitance the voltage will add, if the voltages
are not equal then there are problems. Resistors are needed across the
capacitors when equal values of capacitors are used. This is mainly due
to the wide variation of capacitance in most of them. Helps to bleed
off the stored charge also.

 

[Adrian Caspersz]

On 14/11/16 21:58, pfjw@aol.com wrote:

Nor would I ever run caps of differing voltage in series. Or parallel for that matter.

I will report my results.

Again, here is the link. I am NOT making this up.

https://www.kitronik.co.uk/blog/how-to-calculate-capacitors-in-series-and-parallel/

Read Ralphs post again?

Example 1:

C1 = 20, C2 = 20

not 10 ...

--
Adrian C

 

[John Robertson]

On 201611/14/ 1:58 PM, pfjw@aol.com wrote:

On Monday, November 14, 2016 at 4:46:42 PM UTC-5, Ralph Mowery wrote:
In article <6fc1c49e-9ee2-4471-8eaf-7746c5246c9c@googlegroups.com>,
pfjw@aol.com says...

On Monday, November 14, 2016 at 4:13:07 PM UTC-5, jurb...@gmail.com wrote:
"Two caps in series must be calculated, but keeping it very >simple, if two 20uF @ 450V are connected in series, the >actual capacitance will be 5uF @ 900V. "

That's not what I "heard". It should be 10 uF.

(C1 x C2) / (C1 + C2) = Working Capacitance is the equation I have used these many years.

Example 1:

10 x 10 = 100
10 + 10 = 20
100 / 20 = 5

Example 2 (from the link):

10 x 22 = 220
10 + 22 = 32
220 / 32 = 6.875

At least where I come from.

Peter Wieck
Melrose Park, PA


If equal value capacitors are in series (same for resistors in parallel)
all you have to do is devide the value of one of them by the number.
That would be 20 devided by 2 for 10.

You can also take the long hard way and do the product over the sum as
in your example. You just need to LOOK AT THE VALUE IN THE EXAMPLE AS
BEING 20 INSTEAD OF THE 10 FOR EACH ONE THAT YOU USED.

For equal values of capacitance the voltage will add, if the voltages
are not equal then there are problems. Resistors are needed across the
capacitors when equal values of capacitors are used. This is mainly due
to the wide variation of capacitance in most of them. Helps to bleed
off the stored charge also.

OK - I have enough stray caps at home to do a lash-up and I have enough very accurate meters to test the actual results of that lash-up. But, I just rebuilt the power-supply of my Dynaco ST-70 and my actual working results were as the equation implied, as I remember.

Nor would I ever run caps of differing voltage in series. Or parallel for that matter.

I will report my results.

Again, here is the link. I am NOT making this up.

https://www.kitronik.co.uk/blog/how-to-calculate-capacitors-in-series-and-parallel/

Peter Wieck
Melrose Park, PA

The previous poster was simply pointing out that you made an error in
your math. You had a 10uf and a 20uf cap as your math components based
on the link, but were speaking of two 20uf caps in series in the
preceding text.

20*20=400
20+20=40
400/40 = 10uf

For two identical value caps in series divide be two for the resulting
capacitance. Voltage is added. If there are differences in the
capacitance between the two caps then the formula is needed.

Hey, we all make mistakes, even I've made one or two (a minute)...

John ;-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

On Mon, 14 Nov 2016 12:20:23 -0800 (PST), "pfjw@aol.com"
<pfjw@aol.com> wrote:

Forgive the top posting but WARNING: if a big honking electrolytic capacitor that is more than 60 years old is rattling when shaken, it is absolutely and irredeemingly, irrevocably TOAST. As are its siblings. Reforming is an exercise in futility, and possibly very dangerous, as if by some chance you do actually reform one (or more) for the moment, and it should fail under actual use, all the work previous would be for naught. **POW**.

Agree on the photoflash caps in any case. However, I suspect that the OEM caps are vastly oversize to make up for their rather slow chemistry.

Peter Wieck
Melrose Park, PA

On Monday, November 14, 2016 at 2:57:48 PM UTC-5, John Robertson wrote:
On 201611/14/ 11:12 AM, pfjw@aol.com wrote:
First, where are you? All the tubes you mention are quite common and not very expensive. I probably have all of them in my rather random connection. The bigger issue are those capacitors.

Please note the interpolations.

On Monday, November 14, 2016 at 1:34:55 PM UTC-5, et...@whidbey.com wrote:
All,
I know almost nothing about tubes(AKA valves). My son bought a
capacitor discharge spotwelder that uses tubes. It doesn't work. Parts
of it do but on the whole it appears that it doesn't charge the caps.
There are three types of tubes in the thing.
3 each OA2WA voltage regulators
2 each 2D21 thyratrons
1 each 5U4GB rectifier
There are also 6 each physically large electrolytic caps that are,
I believe, rated for 450 volts. They are made by Sprague and are
marked 200-450. No uf markings though. Apparently a couple rattle when
shaken-probably not a good sign.

200uF @ 450V. You could pay anywhere from $15 to $100 for those caps. Given the application, do not cheap out, but get as high a quality as you can afford. You also have the choice to put caps in parallel to make the capacity - and series/parallel to make a higher working voltage. There is plenty of room given the size of modern caps to go this route.


There are two transformers. The first has many taps and the second
is connected through a relay to the bank of caps. The secondary of
this xmfr is the spotwelder output.
As near as I can tell the circuit basically operates like so: The
first xmfr provides 450 volts AC which goes through the 5U4GB tube to
be rectified and then through three OA2WA tubes which are connected
in series. From there the power goes to the cap bank and charges the
caps. And from the caps through a big relay to the output xmfr.
The OA2WA tubes have only two of the pins connected. So power goes
in one pin and then out the other to the next OA2WA tube and so on. It
looks like there is no output from the last tube in the series. So
maybe this is why the caps won't charge.


I suggest you consider PHOTOFLASH rated caps - they have a very fast
discharge (low internal ESR - you might want to get a Blue ESR meter to
test these caps) and aren't too expensive...

http://ca.mouser.com/Passive-Components/Capacitors/_/N-5g7r?Keyword=photoflash&FS=True

Look up REFORMING capacitors. Even old ones like yours may be saved,
there was a recent thesis published that showed how large value caps can
last a long time if they are reformed carefully.

2D21's are very old design - there are many circuits online to replace
them with SCRs if you want to bring the machine up to the 21st century...

Likewise your 5U4s, this can be replaced with a solid state bridge (dual
diode) rectifier. As the 5U4 has its own transformer then you need to
make sure it is fused correctly on the primary side in case of a shorted
diode.

OA2 tubes are 150VDC regulators, so with three of them the output is
regulated to 450VDC. If the OA2s are glowing purple then they are at
their regulated voltage (more or less) - all three need to be glowing
for your 450VDC to be regulated. I would expect them to be across the
output of the 5U4 to ground to regulate the output voltage...

John :-#)#


It is probably a blessing that your rectifier (5U4) tube does not work. Were you to be passing B+ - well, the results may be unhappy - see below.

At least one 2D21 thyratron seems to work because the relay that
connects the cap bank works when the machine is triggered.
I would like to know how to test the tubes without a tube tester.

Other than for filament continuity and gross shorts (shorts on a cold tube), no you have no certain way to test tubes without a tester.

Maybe this means I will need to make a tester. I also would like to
know how to test the big caps. My meter has a cap test function but it
doesn't seem to work with these big caps. Maybe this is because the
caps are high voltage types. Is it (fairly) safe to attempt charging
the caps with line voltage (120 volts) by first rectifying and then
passing the current through a resistor and then to the caps?
Here is a link to pics my son took of the guts of the spotwelder:
https://goo.gl/photos/LF4JKeGyA4YWiCwv9
Any comments about the spotwelder would be much appreciated.
Thanks,
Eric

The big caps are toast - full stop. DO NOT EVEN TRY to operate the tester without them as it is possible to do permanent damage to the transformers if the caps are shorted.

If you are anywhere near the Melrose Park section of Cheltenham Township (Philadelphia area) let me know. Despite the size and industrial application, this is a fairly basic issue to troubleshoot.

Now, showing my age, I used one of those ancient beasts some 40 years ago when I was working as a machinist. When set up properly, they are amazingly versatile. I used one to weld various thickness of inconel wave washers and pimple washers onto stainless steel seal backs for aircraft and nuclear applications. From stuff that was almost as thin as paper (0.004 thick) to stuff as thick as index card stock - dial in the machine, pass the pull-tests and it would hold the setting, effectively, until changed. There was a small stash of tubes above the machine - but no 2D21s. When one of them died one way, I found it at Leon Fertik's establishment for $1.50. I replaced them both and purchased two spares. The machine shop is still with us and thriving. Leon, sadly gave up his shop after his wife passed.

Best of luck with it - I can think of a lot of uses.... Especially if your son is an artist.

Peter Wieck
Melrose Park, PA



--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

I found 220 mfd 450 caps at JustRadio.com. I'm not sure if these will
discharge fast enough. I emailed the site and am waiting for an
answer. A quick search for photoflash caps turns up 300 volt caps, no
450 volt caps. So I'll wait to see if Just Radio thinks its caps are
up to the job. I have decided to just change out all the caps in the
thing if the correct main big caps are available at a reasonable
price. I don't think I want to go through the trouble of coming up
with solid state solutions and then rewiring the unit just yet. If it
worked that well in the past with tubes and if they have reasonable
lifetimes I'll just keep it the way it is. On the other hand, it is my
son's machine and he can do whatever he wants with it, no matter what
kind of help dad wants to give.
Eric

 

[Ralph Mowery]

In article <q5fk2cppqo2i0v69gdvdcq3bu5f147u9b7@4ax.com>,
etpm@whidbey.com says...

"Old pinballers never die, they just flip out."
I found 220 mfd 450 caps at JustRadio.com. I'm not sure if these will

The 220 mfd will work fine where the 200 mfd caps are used. Many of
them have a large tolerance of 20 to 50 %or more.

 

[John Robertson]

On 201611/14/ 2:45 PM, etpm@whidbey.com wrote:

On Mon, 14 Nov 2016 12:20:23 -0800 (PST), "pfjw@aol.com"
pfjw@aol.com> wrote:

Forgive the top posting but WARNING: if a big honking electrolytic capacitor that is more than 60 years old is rattling when shaken, it is absolutely and irredeemingly, irrevocably TOAST. As are its siblings. Reforming is an exercise in futility, and possibly very dangerous, as if by some chance you do actually reform one (or more) for the moment, and it should fail under actual use, all the work previous would be for naught. **POW**.

Agree on the photoflash caps in any case. However, I suspect that the OEM caps are vastly oversize to make up for their rather slow chemistry.

Peter Wieck
Melrose Park, PA

On Monday, November 14, 2016 at 2:57:48 PM UTC-5, John Robertson wrote:
On 201611/14/ 11:12 AM, pfjw@aol.com wrote:
First, where are you? All the tubes you mention are quite common and not very expensive. I probably have all of them in my rather random connection. The bigger issue are those capacitors.

Please note the interpolations.

On Monday, November 14, 2016 at 1:34:55 PM UTC-5, et...@whidbey.com wrote:
All,
I know almost nothing about tubes(AKA valves). My son bought a
capacitor discharge spotwelder that uses tubes. It doesn't work. Parts
of it do but on the whole it appears that it doesn't charge the caps.
There are three types of tubes in the thing.
3 each OA2WA voltage regulators
2 each 2D21 thyratrons
1 each 5U4GB rectifier
There are also 6 each physically large electrolytic caps that are,
I believe, rated for 450 volts. They are made by Sprague and are
marked 200-450. No uf markings though. Apparently a couple rattle when
shaken-probably not a good sign.

200uF @ 450V. You could pay anywhere from $15 to $100 for those caps. Given the application, do not cheap out, but get as high a quality as you can afford. You also have the choice to put caps in parallel to make the capacity - and series/parallel to make a higher working voltage. There is plenty of room given the size of modern caps to go this route.


There are two transformers. The first has many taps and the second
is connected through a relay to the bank of caps. The secondary of
this xmfr is the spotwelder output.
As near as I can tell the circuit basically operates like so: The
first xmfr provides 450 volts AC which goes through the 5U4GB tube to
be rectified and then through three OA2WA tubes which are connected
in series. From there the power goes to the cap bank and charges the
caps. And from the caps through a big relay to the output xmfr.
The OA2WA tubes have only two of the pins connected. So power goes
in one pin and then out the other to the next OA2WA tube and so on. It
looks like there is no output from the last tube in the series. So
maybe this is why the caps won't charge.


I suggest you consider PHOTOFLASH rated caps - they have a very fast
discharge (low internal ESR - you might want to get a Blue ESR meter to
test these caps) and aren't too expensive...

http://ca.mouser.com/Passive-Components/Capacitors/_/N-5g7r?Keyword=photoflash&FS=True

Look up REFORMING capacitors. Even old ones like yours may be saved,
there was a recent thesis published that showed how large value caps can
last a long time if they are reformed carefully.

2D21's are very old design - there are many circuits online to replace
them with SCRs if you want to bring the machine up to the 21st century...

Likewise your 5U4s, this can be replaced with a solid state bridge (dual
diode) rectifier. As the 5U4 has its own transformer then you need to
make sure it is fused correctly on the primary side in case of a shorted
diode.

OA2 tubes are 150VDC regulators, so with three of them the output is
regulated to 450VDC. If the OA2s are glowing purple then they are at
their regulated voltage (more or less) - all three need to be glowing
for your 450VDC to be regulated. I would expect them to be across the
output of the 5U4 to ground to regulate the output voltage...

John :-#)#


It is probably a blessing that your rectifier (5U4) tube does not work. Were you to be passing B+ - well, the results may be unhappy - see below.

At least one 2D21 thyratron seems to work because the relay that
connects the cap bank works when the machine is triggered.
I would like to know how to test the tubes without a tube tester.

Other than for filament continuity and gross shorts (shorts on a cold tube), no you have no certain way to test tubes without a tester.

Maybe this means I will need to make a tester. I also would like to
know how to test the big caps. My meter has a cap test function but it
doesn't seem to work with these big caps. Maybe this is because the
caps are high voltage types. Is it (fairly) safe to attempt charging
the caps with line voltage (120 volts) by first rectifying and then
passing the current through a resistor and then to the caps?
Here is a link to pics my son took of the guts of the spotwelder:
https://goo.gl/photos/LF4JKeGyA4YWiCwv9
Any comments about the spotwelder would be much appreciated.
Thanks,
Eric

The big caps are toast - full stop. DO NOT EVEN TRY to operate the tester without them as it is possible to do permanent damage to the transformers if the caps are shorted.

If you are anywhere near the Melrose Park section of Cheltenham Township (Philadelphia area) let me know. Despite the size and industrial application, this is a fairly basic issue to troubleshoot.

Now, showing my age, I used one of those ancient beasts some 40 years ago when I was working as a machinist. When set up properly, they are amazingly versatile. I used one to weld various thickness of inconel wave washers and pimple washers onto stainless steel seal backs for aircraft and nuclear applications. From stuff that was almost as thin as paper (0.004 thick) to stuff as thick as index card stock - dial in the machine, pass the pull-tests and it would hold the setting, effectively, until changed. There was a small stash of tubes above the machine - but no 2D21s. When one of them died one way, I found it at Leon Fertik's establishment for $1.50. I replaced them both and purchased two spares. The machine shop is still with us and thriving. Leon, sadly gave up his shop after his wife passed.

Best of luck with it - I can think of a lot of uses.... Especially if your son is an artist.

Peter Wieck
Melrose Park, PA



--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
I found 220 mfd 450 caps at JustRadio.com. I'm not sure if these will
discharge fast enough. I emailed the site and am waiting for an
answer. A quick search for photoflash caps turns up 300 volt caps, no
450 volt caps. So I'll wait to see if Just Radio thinks its caps are
up to the job. I have decided to just change out all the caps in the
thing if the correct main big caps are available at a reasonable
price. I don't think I want to go through the trouble of coming up
with solid state solutions and then rewiring the unit just yet. If it
worked that well in the past with tubes and if they have reasonable
lifetimes I'll just keep it the way it is. On the other hand, it is my
son's machine and he can do whatever he wants with it, no matter what
kind of help dad wants to give.
Eric

Did you look at the Mouser link I included a few posts ago? They list
400 and 500VDC Photoflash caps. Mind you, you need to order one to two
hundred.

http://ca.mouser.com/Passive-Components/Capacitors/_/N-5g7r?Keyword=photoflash&FS=True

Here is a surplus place with photoflash caps, not cheap, but they are in
stock:

https://www.surplussales.com/capacitors/Electrolytics/eaf.html

However, if you use the part number you will probably find a stocking
distributor...

JustRadio sells good caps, but they aren't photoflash rated - pretty
safe bet on that!

John :-#)#

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(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[mike]

On 11/14/2016 3:15 PM, Ralph Mowery wrote:

In article <q5fk2cppqo2i0v69gdvdcq3bu5f147u9b7@4ax.com>,
etpm@whidbey.com says...

"Old pinballers never die, they just flip out."
I found 220 mfd 450 caps at JustRadio.com. I'm not sure if these will

The 220 mfd will work fine where the 200 mfd caps are used. Many of
them have a large tolerance of 20 to 50 %or more.


Might be helpful to take a peek below the obvious.

Take a close look at the pix of the capacitors at the mouser link.
Compare the solder pins to the size of the buss bars in the welder.
At least you'll be able to say you thought about the consequences
of tiny pins and dubious solder connections. That compounds if you
go with fewer larger caps. All that energy into the weld
came from the caps. It's just as easy to melt the solder at that
end.

Don't go too crazy with the cap values. My spot welder is calibrated
to deliver energy based on the voltage and cap value.
If the cap is different, the calibration can be off by that ratio.
If your meter has a square-law scale, that can make a significant
difference in calibration at one end or the other. You can't
just add a resistor to fix it. But you can put a post-it note
on the panel and do the scale factor in your head.

If you don't have a schematic, create one. It only takes one
wrong assumption to make a lot of smoke.

Beware saturation in the output transformer. Mine has a core reset
pulse between firings. If that part of your system is broke,
you can saturate the core. At best, that can take your diagnostics
down the wrong path. At worst, more smoke that takes out the parts
you just fixed.

Are we having fun yet?

 

[Clifford Heath]

On 15/11/16 12:45, whit3rd wrote:

On Monday, November 14, 2016 at 2:44:55 PM UTC-8, et...@whidbey.com wrote:
I found 220 mfd 450 caps at JustRadio.com. I'm not sure if these will
discharge fast enough.
For a welding purpose, 100l milliseconds is very fast (no functioning
capacitor you are likely to find would have too high ESR for this job).

I agree that the speed doesn't matter, but low ESR caps have wiring that
will survive higher currents. No sense having a whopping cap
with internally-fused connections.

I also have a bench-top spot welder, from my father who was an
orthodontist. It has a 110V input (so we needed a transformer
from 240V), and that feeds via a small Variac into a selenium
rectifier. I suspect the caps need replacing (again - they were
last done 25 years ago) and I have a bunch of 300V photoflash
caps from disposable cameras that I hope will suffice.

The welding contacts are an anvil and an upper contact connected
to the foot pedal, via an adjustable pressure-operated switch
that fires the contacter. That leaves both hands free to hold and
position the work. When you press down hard enough, the thing
fires, very cute.

What I don't know is how to determine the maximum energy I can
dump through the output transformer without saturating it.
Anyone know how I can tell (other than just keeping the
capacitance below the original value)?

Clifford Heath.