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On Mon, 14 Nov 2016 18:25:14 -0500, Tom Biasi wrote:
On 11/14/2016 1:36 PM, etpm@whidbey.com wrote:
Any comments about the spotwelder would be much appreciated.
Thanks,
Eric
You couldn't pay me enough to spot weld with that thing.
Why? It looks well built, if a bit old.
On Tue, 15 Nov 2016 11:53:18 -0500, Tom Biasi wrote:
On 11/15/2016 11:49 AM, Tim Wescott wrote:
On Tue, 15 Nov 2016 11:40:38 -0500, Tom Biasi wrote:
On 11/15/2016 10:56 AM, etpm@whidbey.com wrote:
On Mon, 14 Nov 2016 21:27:33 -0500, Tom Biasi
tombiasi@optonline.net
wrote:
On 11/14/2016 9:17 PM, Tim Wescott wrote:
On Mon, 14 Nov 2016 18:25:14 -0500, Tom Biasi wrote:
On 11/14/2016 1:36 PM, etpm@whidbey.com wrote:
Any comments about the spotwelder would be much appreciated.
Thanks,
Eric
You couldn't pay me enough to spot weld with that thing.
Why? It looks well built, if a bit old.
450 volts capacitive discharge to a piece of metal. No OSHA back
then.
The caps discharge into a large transformer. The spotwelding voltage
must be very low, just a few volts. ALL of the spotwelders I have
ever used were high current, low voltage. Usually around three volts.
Eric
Yes, If the unit is working properly.
If that's your reasoning then don't use any spot welder.
I wasn't looking for a war Tim, I just said what I would do. I have seen
units like that in an old factory, and people have been shocked.
Well, I'm kinda shocked that it looks so modern and in good condition,
yet with toobs.
On Mon, 14 Nov 2016 10:36:41 -0800, etpm@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.
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
I've been following this thread for a time now and for what it is
worth....
Solid state devices have it all over vacuum (and gas) tubes. I worked
in a pharmaceutical plant for several years with antiquated packaging
lines... Where ever we could (and that meant everywhere) we'd replace
those 2D21's with Thyristors (SCR's) and the gas regulators with Zener
diodes or other SS shunt regulators, and the 5U4's with simple 1N4000
series diodes.
It was often lots less work to do it that way then try to find working
vacuum tubes from some antique parts store.
Don't get me wrong.. if you're doing it because you like cheerful
glowing vacuum tubes, or convinced yourself that harmonic distortion
sounds better than negligible distortion, by all means go for it.
I get it. I like varnished oak with brass corners and braces and large
fancy gear trains turning potentiometers etc.. But if you actually want
to use the silly thing, put in solid state components, or design it new
from the ground up. (and you may never have to mess with it again -
something I hate; doing it once is fun, repairing it sucks big time
IMO)
And BTW we had one small bench top cap discharge spot welder that used a
HV source (all new SS) to weld our thermocouples with... Piece of crap
IMO, we would use a low voltage spot welder (cost ~$50 from Harbor
Freight) to do the same job, safely and reliably.
On Tue, 15 Nov 2016 20:27:53 -0500, default wrote:
On Mon, 14 Nov 2016 10:36:41 -0800, etpm@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.
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
I've been following this thread for a time now and for what it is
worth....
Solid state devices have it all over vacuum (and gas) tubes. I worked
in a pharmaceutical plant for several years with antiquated packaging
lines... Where ever we could (and that meant everywhere) we'd replace
those 2D21's with Thyristors (SCR's) and the gas regulators with Zener
diodes or other SS shunt regulators, and the 5U4's with simple 1N4000
series diodes.
It was often lots less work to do it that way then try to find working
vacuum tubes from some antique parts store.
Don't get me wrong.. if you're doing it because you like cheerful
glowing vacuum tubes, or convinced yourself that harmonic distortion
sounds better than negligible distortion, by all means go for it.
I get it. I like varnished oak with brass corners and braces and large
fancy gear trains turning potentiometers etc.. But if you actually want
to use the silly thing, put in solid state components, or design it new
from the ground up. (and you may never have to mess with it again -
something I hate; doing it once is fun, repairing it sucks big time
IMO)
And BTW we had one small bench top cap discharge spot welder that used a
HV source (all new SS) to weld our thermocouples with... Piece of crap
IMO, we would use a low voltage spot welder (cost ~$50 from Harbor
Freight) to do the same job, safely and reliably.
How much do you have to change? Can you just plug in semiconductor
modules where the tubes used to be, or do you have to make other circuit
modifications?
Are you set on making this work or just having a working spot welder?
On Tue, 15 Nov 2016 20:27:53 -0500, default wrote:
On Mon, 14 Nov 2016 10:36:41 -0800, etpm@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.
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
I've been following this thread for a time now and for what it is
worth....
Solid state devices have it all over vacuum (and gas) tubes. I worked
in a pharmaceutical plant for several years with antiquated packaging
lines... Where ever we could (and that meant everywhere) we'd replace
those 2D21's with Thyristors (SCR's) and the gas regulators with Zener
diodes or other SS shunt regulators, and the 5U4's with simple 1N4000
series diodes.
It was often lots less work to do it that way then try to find working
vacuum tubes from some antique parts store.
Don't get me wrong.. if you're doing it because you like cheerful
glowing vacuum tubes, or convinced yourself that harmonic distortion
sounds better than negligible distortion, by all means go for it.
I get it. I like varnished oak with brass corners and braces and large
fancy gear trains turning potentiometers etc.. But if you actually want
to use the silly thing, put in solid state components, or design it new
from the ground up. (and you may never have to mess with it again -
something I hate; doing it once is fun, repairing it sucks big time
IMO)
And BTW we had one small bench top cap discharge spot welder that used a
HV source (all new SS) to weld our thermocouples with... Piece of crap
IMO, we would use a low voltage spot welder (cost ~$50 from Harbor
Freight) to do the same job, safely and reliably.
How much do you have to change? Can you just plug in semiconductor
modules where the tubes used to be, or do you have to make other circuit
modifications?
On Thu, 17 Nov 2016 18:37:18 -0600, Tim Wescott
seemywebsite@myfooter.really> wrote:
On Tue, 15 Nov 2016 20:27:53 -0500, default wrote:
On Mon, 14 Nov 2016 10:36:41 -0800, etpm@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.
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
I've been following this thread for a time now and for what it is
worth....
Solid state devices have it all over vacuum (and gas) tubes. I worked
in a pharmaceutical plant for several years with antiquated packaging
lines... Where ever we could (and that meant everywhere) we'd replace
those 2D21's with Thyristors (SCR's) and the gas regulators with Zener
diodes or other SS shunt regulators, and the 5U4's with simple 1N4000
series diodes.
It was often lots less work to do it that way then try to find working
vacuum tubes from some antique parts store.
Don't get me wrong.. if you're doing it because you like cheerful
glowing vacuum tubes, or convinced yourself that harmonic distortion
sounds better than negligible distortion, by all means go for it.
I get it. I like varnished oak with brass corners and braces and
large fancy gear trains turning potentiometers etc.. But if you
actually want to use the silly thing, put in solid state components,
or design it new from the ground up. (and you may never have to mess
with it again - something I hate; doing it once is fun, repairing it
sucks big time IMO)
And BTW we had one small bench top cap discharge spot welder that used
a HV source (all new SS) to weld our thermocouples with... Piece of
crap IMO, we would use a low voltage spot welder (cost ~$50 from
Harbor Freight) to do the same job, safely and reliably.
How much do you have to change? Can you just plug in semiconductor
modules where the tubes used to be, or do you have to make other circuit
modifications?
Most of the changes were relatively minimal. Something like a 5U4
already has plug-in solid state replacements available off the shelf.
The thyristor behaves pretty much the same as a thyratron so replacement
was a matter of checking out the firing circuit and maybe adding a diode
to prevent the negative voltage the thyratron needs in the off state
from reaching the gate ... on a case by case basis. Mounting and
heatsinking were other considerations.
We were paying something like $50 for the 2D21's and sourcing and
stocking them was a problem so it paid to spend a little time tinkering
to make it work. AND there's nothing like having a packaging line go
down at midnight to motivate people to find an alternative...
In the case of gas shunt regulators they were mainly relatively low
current devices used in vacuum tube biasing supplies and back in the day
we could often find zeners with similar specifications or by stringing
several in series to dissipate the power at the necessary voltages.
Something like 1-5 watts in the case of an 0A2 (if my memory serves me)
And unlike the 0A2, ambient light doesn't affect the firing voltage...
On Mon, 14 Nov 2016 10:36:41 -0800, etpm@whidbey.com wrote:
PS
In the case of 5U4 and other rectifiers, I've often wondered what the
warm-up characteristics might have done to prolong the life of other
vacuum tubes in the circuits.
Back in the day, especially the early days, it was understood that you
didn't want to apply plate voltage until the cathodes were up to
temperature. The theory behind it was that while the cathodes were
warming up from a cold start there would be uneven heating in the case
of indirectly heated cathodes (and coated filaments) and the strong
electrostatic field would cause bits of the emissive coatings to be
ripped from the cathodes. Or so we were told...
This was especially true of large transmitting tubes because of the
physical size, high voltages and powers present - and no doubt the cost
of replacements. There'd often be a timed relay that would apply plate
power after the tubes had a chance to heat.
Which makes me wonder about microwave ovens with their 2KV, 1000 watt
vacuum tubes... Maybe coatings or cathode structures have improved?
Unitek. They are still making spot welders but have been bought up byTim Wescott <tim@seemywebsite.com> wrote:
On Mon, 14 Nov 2016 18:25:14 -0500, Tom Biasi wrote:
On 11/14/2016 1:36 PM, etpm@whidbey.com wrote:
Any comments about the spotwelder would be much appreciated.
Thanks,
Eric
You couldn't pay me enough to spot weld with that thing.
Why? It looks well built, if a bit old.
I was thinking it looks rather "new" to be packed with tubes and the
constuction is good. What company made it?