Tubes in broken spotwelder & other questions

Nov 15, 2016

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

Tim Wescott · Nov 15, 2016

On Mon, 14 Nov 2016 10:36:41 -0800, etpm wrote:

All,
I know almost nothing about tubes(AKA valves).

Round. Shiny. Get hot. They hold the magic smoke so well, it usually
spurts out of some other part of the circuit when they break. What more
do you need to know?

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.

Probably 200uF, but I won't weep if I'm found to be wrong.

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.

Charging the caps through the voltage regulators would be dumb, and may
even overheat the tubes, so I'm not sure I believe it. Much more likely
is that they're being used to generate a regulated 450VDC supply
someplace (the OA2 is a nominal 150V regulator). I'd claim that they're
there to protect the caps, but they have a strike voltage of 185V, three
times which is greater than the voltage rating on the caps -- and smart
engineers never run their 'lytics at full voltage rating.

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.

Did you find this by measurement, or what? Industrial circuits do thingsn
that I find weird so I could be wrong, but I would expect the chain of
regulator tubes to end at ground.

Gas regulator tubes like that are basically neon lights, only they're not
for making light and the gas mix may not have neon. The gas mix and the
electrode spacing is selected for the desired voltage drop. IIRC, those
will light up blue or purple if they're working -- but it's been a
while. They'll light up with some visible color, although the room may
need to be dim to see them. So dim the lights and look.

At least one 2D21 thyratron seems to work because the relay that
connects the cap bank works when the machine is triggered.

I would expect that if the circuit has thyratrons in it at all, that they
are there for closing the primary power circuit, not for closing the
relay. I could be wrong (and those are dinky little tubes, which makes
me think I might indeed be wrong), but I'd only feel sure of that if I
knew that the thyratron anodes were connected to the relay coil, rather
than the secondary.

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

Have you typed the model information into Google and seen if any
schematics pop up? This whole job is really best done if you know the
schematic. I think that if I was as far along as you were in this I'd be
spending some quality time with the welder, an ohmmeter, a pencil and
paper, and tracing the schematic out by hand -- assuming I couldn't find
it on the web.

You talk about hearing the relay click -- does that mean that you've had
the thing plugged in? If you've had it plugged in and smoke didn't pour
out, then it's passed the first test and you can probably safely play
with it (well, as safely as you can do any probing around in a circuit
with at least 450V on it).

Yes, you can test the caps in the way you suggest, at least to some
extent. The one that rattles is probably dead. Charge each one up and
note the current it draws when charged up (Google "capacitor reforming"
if you want to do the whole dance). Then, if you have a storage
oscilloscope, discharge each one through a known resistance and look at
how quickly the voltage drops (or discharge one through a big enough
resistance that you can watch on a voltmeter). Assuming that they'll
hold charge for a minute or so by themselves, when you put a resistor on
the amount of time that it takes them to get from full voltage to 38% of
full is the RC time constant of the circuit -- if you know the resistance
and the time, you can solve t = RC for the capacitance.

If you've had the thing running, and you know how to be safe around
voltages like that then I suggest you trace out the schematic, or try to
obtain one, then test things in operation (Google for procedures -- 450V
can leave you dead before you realize it, and I don't want to be reading
your obituary).

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

Ralph Mowery · Nov 15, 2016

In article <4huj2c9po9e6d9ee1idtcq5nfkv4ncamgm@4ax.com>,
etpm@whidbey.com says...

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

Do you know anythng about electronics at all ? Maybe the solid state
electronics.

The capacitors marked 200 450 mean they are 200 mfd and rated to run at
up to 450 volts on them. They don't have to have that much, just the
maximum.

The 0A2 tubes are like big neon bulbs. The show glow a blue color when
working. You can look up the voltage as I don't want to. Somewhere
around 100 to 150 volts will be required to make them glow. When
glowing they regulate the voltage to that value. Only 2 pins are needed
for them.

You can get an idea of the capacitors if you have an old analog ohm
meter or multimeter. Go to a high ohms scale and see how if the ohms
show very low to start with and after several seconds the ohms should go
to almost an open circuit indication. This will probably have to be
done with atleast one side out of the circuit.

The 5U4 should have a filiment you can see glowing. There are 2 pins
connected to the 2 plates. You should get pulsating DC from each plate
to the ground or common connection point probably where the negative
lead of the capacitors are.
If the capacitors are good or sort of working the DC will be steady.

Tim Wescott · Nov 15, 2016

On Mon, 14 Nov 2016 13:15:18 -0600, Tim Wescott wrote:

On Mon, 14 Nov 2016 10:36:41 -0800, etpm wrote:

All,
I know almost nothing about tubes(AKA valves).

Round. Shiny. Get hot. They hold the magic smoke so well, it usually
spurts out of some other part of the circuit when they break. What more
do you need to know?

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.

Probably 200uF, but I won't weep if I'm found to be wrong.

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.

Charging the caps through the voltage regulators would be dumb, and may
even overheat the tubes, so I'm not sure I believe it. Much more likely
is that they're being used to generate a regulated 450VDC supply
someplace (the OA2 is a nominal 150V regulator). I'd claim that they're
there to protect the caps, but they have a strike voltage of 185V, three
times which is greater than the voltage rating on the caps -- and smart
engineers never run their 'lytics at full voltage rating.

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.

Did you find this by measurement, or what? Industrial circuits do
thingsn that I find weird so I could be wrong, but I would expect the
chain of regulator tubes to end at ground.

Gas regulator tubes like that are basically neon lights, only they're
not for making light and the gas mix may not have neon. The gas mix and
the electrode spacing is selected for the desired voltage drop. IIRC,
those will light up blue or purple if they're working -- but it's been a
while. They'll light up with some visible color, although the room may
need to be dim to see them. So dim the lights and look.

At least one 2D21 thyratron seems to work because the relay that
connects the cap bank works when the machine is triggered.

I would expect that if the circuit has thyratrons in it at all, that
they are there for closing the primary power circuit, not for closing
the relay. I could be wrong (and those are dinky little tubes, which
makes me think I might indeed be wrong), but I'd only feel sure of that
if I knew that the thyratron anodes were connected to the relay coil,
rather than the secondary.

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

Have you typed the model information into Google and seen if any
schematics pop up? This whole job is really best done if you know the
schematic. I think that if I was as far along as you were in this I'd
be spending some quality time with the welder, an ohmmeter, a pencil and
paper, and tracing the schematic out by hand -- assuming I couldn't find
it on the web.

You talk about hearing the relay click -- does that mean that you've had
the thing plugged in? If you've had it plugged in and smoke didn't pour
out, then it's passed the first test and you can probably safely play
with it (well, as safely as you can do any probing around in a circuit
with at least 450V on it).

Yes, you can test the caps in the way you suggest, at least to some
extent. The one that rattles is probably dead. Charge each one up and
note the current it draws when charged up (Google "capacitor reforming"
if you want to do the whole dance). Then, if you have a storage
oscilloscope, discharge each one through a known resistance and look at
how quickly the voltage drops (or discharge one through a big enough
resistance that you can watch on a voltmeter). Assuming that they'll
hold charge for a minute or so by themselves, when you put a resistor on
the amount of time that it takes them to get from full voltage to 38% of
full is the RC time constant of the circuit -- if you know the
resistance and the time, you can solve t = RC for the capacitance.

If you've had the thing running, and you know how to be safe around
voltages like that then I suggest you trace out the schematic, or try to
obtain one, then test things in operation (Google for procedures -- 450V
can leave you dead before you realize it, and I don't want to be reading
your obituary).

Oops -- I pulled up the 2D21 data sheet but only noticed the following
when I went to close that browser tab: " ... designed for use in relay
applications ... ". So it could just be there to make the relay work.

I'm a bit puzzled, because unless that's one honkin' big relay, it seems
like the capacitor bank is too large to be consistent with just turning
it on, but the power transformer is too damned small to weld with. I'm
leaving all my ramblings above intact, but check if the welding
transformer doesn't just go straight to the input power -- I'm wondering
if all the fancy electronics aren't just there to set the timing on the
pulse, and the actual welding power is AC (why not?) and steered by the
relay.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

Jim Thompson · Nov 15, 2016

On Mon, 14 Nov 2016 13:15:18 -0600, Tim Wescott
<seemywebsite@myfooter.really> wrote:

On Mon, 14 Nov 2016 10:36:41 -0800, etpm wrote:

All,
I know almost nothing about tubes(AKA valves).

Round. Shiny. Get hot. They hold the magic smoke so well, it usually
spurts out of some other part of the circuit when they break. What more
do you need to know?

[snip]

Nov 15, 2016

On Mon, 14 Nov 2016 13:21:39 -0600, Tim Wescott
<seemywebsite@myfooter.really> wrote:

On Mon, 14 Nov 2016 13:15:18 -0600, Tim Wescott wrote:

On Mon, 14 Nov 2016 10:36:41 -0800, etpm wrote:

All,
I know almost nothing about tubes(AKA valves).

Round. Shiny. Get hot. They hold the magic smoke so well, it usually
spurts out of some other part of the circuit when they break. What more
do you need to know?

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.

Probably 200uF, but I won't weep if I'm found to be wrong.

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.

Charging the caps through the voltage regulators would be dumb, and may
even overheat the tubes, so I'm not sure I believe it. Much more likely
is that they're being used to generate a regulated 450VDC supply
someplace (the OA2 is a nominal 150V regulator). I'd claim that they're
there to protect the caps, but they have a strike voltage of 185V, three
times which is greater than the voltage rating on the caps -- and smart
engineers never run their 'lytics at full voltage rating.

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.

Did you find this by measurement, or what? Industrial circuits do
thingsn that I find weird so I could be wrong, but I would expect the
chain of regulator tubes to end at ground.

Gas regulator tubes like that are basically neon lights, only they're
not for making light and the gas mix may not have neon. The gas mix and
the electrode spacing is selected for the desired voltage drop. IIRC,
those will light up blue or purple if they're working -- but it's been a
while. They'll light up with some visible color, although the room may
need to be dim to see them. So dim the lights and look.

At least one 2D21 thyratron seems to work because the relay that
connects the cap bank works when the machine is triggered.

I would expect that if the circuit has thyratrons in it at all, that
they are there for closing the primary power circuit, not for closing
the relay. I could be wrong (and those are dinky little tubes, which
makes me think I might indeed be wrong), but I'd only feel sure of that
if I knew that the thyratron anodes were connected to the relay coil,
rather than the secondary.

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

Have you typed the model information into Google and seen if any
schematics pop up? This whole job is really best done if you know the
schematic. I think that if I was as far along as you were in this I'd
be spending some quality time with the welder, an ohmmeter, a pencil and
paper, and tracing the schematic out by hand -- assuming I couldn't find
it on the web.

You talk about hearing the relay click -- does that mean that you've had
the thing plugged in? If you've had it plugged in and smoke didn't pour
out, then it's passed the first test and you can probably safely play
with it (well, as safely as you can do any probing around in a circuit
with at least 450V on it).

Yes, you can test the caps in the way you suggest, at least to some
extent. The one that rattles is probably dead. Charge each one up and
note the current it draws when charged up (Google "capacitor reforming"
if you want to do the whole dance). Then, if you have a storage
oscilloscope, discharge each one through a known resistance and look at
how quickly the voltage drops (or discharge one through a big enough
resistance that you can watch on a voltmeter). Assuming that they'll
hold charge for a minute or so by themselves, when you put a resistor on
the amount of time that it takes them to get from full voltage to 38% of
full is the RC time constant of the circuit -- if you know the
resistance and the time, you can solve t = RC for the capacitance.

If you've had the thing running, and you know how to be safe around
voltages like that then I suggest you trace out the schematic, or try to
obtain one, then test things in operation (Google for procedures -- 450V
can leave you dead before you realize it, and I don't want to be reading
your obituary).

Oops -- I pulled up the 2D21 data sheet but only noticed the following
when I went to close that browser tab: " ... designed for use in relay
applications ... ". So it could just be there to make the relay work.

I'm a bit puzzled, because unless that's one honkin' big relay, it seems
like the capacitor bank is too large to be consistent with just turning
it on, but the power transformer is too damned small to weld with. I'm
leaving all my ramblings above intact, but check if the welding
transformer doesn't just go straight to the input power -- I'm wondering
if all the fancy electronics aren't just there to set the timing on the
pulse, and the actual welding power is AC (why not?) and steered by the
relay.

The relay works-I saw it working. And it does indeed connect the cap
bank to the output xmfr. The connections are obvious. And the relay
contacts are big, like a contactor.

Nov 15, 2016

On Mon, 14 Nov 2016 14:20:02 -0500, Ralph Mowery
<rmowery28146@earthlink.net> wrote:

In article <4huj2c9po9e6d9ee1idtcq5nfkv4ncamgm@4ax.com>,
etpm@whidbey.com says...

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

Do you know anythng about electronics at all ? Maybe the solid state
electronics.

The capacitors marked 200 450 mean they are 200 mfd and rated to run at
up to 450 volts on them. They don't have to have that much, just the
maximum.

The 0A2 tubes are like big neon bulbs. The show glow a blue color when
working. You can look up the voltage as I don't want to. Somewhere
around 100 to 150 volts will be required to make them glow. When
glowing they regulate the voltage to that value. Only 2 pins are needed
for them.

You can get an idea of the capacitors if you have an old analog ohm
meter or multimeter. Go to a high ohms scale and see how if the ohms
show very low to start with and after several seconds the ohms should go
to almost an open circuit indication. This will probably have to be
done with atleast one side out of the circuit.

The 5U4 should have a filiment you can see glowing. There are 2 pins
connected to the 2 plates. You should get pulsating DC from each plate
to the ground or common connection point probably where the negative
lead of the capacitors are.
If the capacitors are good or sort of working the DC will be steady.

Thanks for the reply Ralph. Especially the info about the large caps.
I do OK with solid state stuff but tubes are a mystery to me because I
have never really needed to work with them or test them. My son has
googled for a schematic but so far no luck. It may be that he will
need to trace it out himself.
Eric

amdx · Nov 15, 2016

On 11/14/2016 1:44 PM, etpm@whidbey.com wrote:

On Mon, 14 Nov 2016 14:20:02 -0500, Ralph Mowery
rmowery28146@earthlink.net> wrote:

In article <4huj2c9po9e6d9ee1idtcq5nfkv4ncamgm@4ax.com>,
etpm@whidbey.com says...

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

Do you know anythng about electronics at all ? Maybe the solid state
electronics.

The capacitors marked 200 450 mean they are 200 mfd and rated to run at
up to 450 volts on them. They don't have to have that much, just the
maximum.

The 0A2 tubes are like big neon bulbs. The show glow a blue color when
working. You can look up the voltage as I don't want to. Somewhere
around 100 to 150 volts will be required to make them glow. When
glowing they regulate the voltage to that value. Only 2 pins are needed
for them.

You can get an idea of the capacitors if you have an old analog ohm
meter or multimeter. Go to a high ohms scale and see how if the ohms
show very low to start with and after several seconds the ohms should go
to almost an open circuit indication. This will probably have to be
done with atleast one side out of the circuit.

The 5U4 should have a filiment you can see glowing. There are 2 pins
connected to the 2 plates. You should get pulsating DC from each plate
to the ground or common connection point probably where the negative
lead of the capacitors are.
If the capacitors are good or sort of working the DC will be steady.
Thanks for the reply Ralph. Especially the info about the large caps.
I do OK with solid state stuff but tubes are a mystery to me because I
have never really needed to work with them or test them. My son has
googled for a schematic but so far no luck. It may be that he will
need to trace it out himself.
Eric

The OA2s are like zener diodes and they are 150V. I would say they
have 3 in series to get a regulated 450V to charge the caps, BUT then
why are the caps only rated at 450V? I've been working on a device that
has an OA2 and an OB2 in series for a regulated 258Vdc. Must be the OB2
is a 108V regulator.
Just my 2 cents to add to the confusion.
Mikek

Jim Thompson · Nov 15, 2016

On Mon, 14 Nov 2016 11:44:23 -0800, etpm@whidbey.com wrote:

On Mon, 14 Nov 2016 14:20:02 -0500, Ralph Mowery
rmowery28146@earthlink.net> wrote:

In article <4huj2c9po9e6d9ee1idtcq5nfkv4ncamgm@4ax.com>,
etpm@whidbey.com says...

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

Do you know anythng about electronics at all ? Maybe the solid state
electronics.

The capacitors marked 200 450 mean they are 200 mfd and rated to run at
up to 450 volts on them. They don't have to have that much, just the
maximum.

The 0A2 tubes are like big neon bulbs. The show glow a blue color when
working. You can look up the voltage as I don't want to. Somewhere
around 100 to 150 volts will be required to make them glow. When
glowing they regulate the voltage to that value. Only 2 pins are needed
for them.

You can get an idea of the capacitors if you have an old analog ohm
meter or multimeter. Go to a high ohms scale and see how if the ohms
show very low to start with and after several seconds the ohms should go
to almost an open circuit indication. This will probably have to be
done with atleast one side out of the circuit.

The 5U4 should have a filiment you can see glowing. There are 2 pins
connected to the 2 plates. You should get pulsating DC from each plate
to the ground or common connection point probably where the negative
lead of the capacitors are.
If the capacitors are good or sort of working the DC will be steady.
Thanks for the reply Ralph. Especially the info about the large caps.
I do OK with solid state stuff but tubes are a mystery to me because I
have never really needed to work with them or test them. My son has
googled for a schematic but so far no luck. It may be that he will
need to trace it out himself.
Eric

Jim Thompson · Nov 15, 2016

On Mon, 14 Nov 2016 14:16:46 -0600, amdx <nojunk@knology.net> wrote:

On 11/14/2016 1:44 PM, etpm@whidbey.com wrote:
On Mon, 14 Nov 2016 14:20:02 -0500, Ralph Mowery
rmowery28146@earthlink.net> wrote:

In article <4huj2c9po9e6d9ee1idtcq5nfkv4ncamgm@4ax.com>,
etpm@whidbey.com says...

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

Do you know anythng about electronics at all ? Maybe the solid state
electronics.

The capacitors marked 200 450 mean they are 200 mfd and rated to run at
up to 450 volts on them. They don't have to have that much, just the
maximum.

The 0A2 tubes are like big neon bulbs. The show glow a blue color when
working. You can look up the voltage as I don't want to. Somewhere
around 100 to 150 volts will be required to make them glow. When
glowing they regulate the voltage to that value. Only 2 pins are needed
for them.

You can get an idea of the capacitors if you have an old analog ohm
meter or multimeter. Go to a high ohms scale and see how if the ohms
show very low to start with and after several seconds the ohms should go
to almost an open circuit indication. This will probably have to be
done with atleast one side out of the circuit.

The 5U4 should have a filiment you can see glowing. There are 2 pins
connected to the 2 plates. You should get pulsating DC from each plate
to the ground or common connection point probably where the negative
lead of the capacitors are.
If the capacitors are good or sort of working the DC will be steady.
Thanks for the reply Ralph. Especially the info about the large caps.
I do OK with solid state stuff but tubes are a mystery to me because I
have never really needed to work with them or test them. My son has
googled for a schematic but so far no luck. It may be that he will
need to trace it out himself.
Eric

The OA2s are like zener diodes and they are 150V. I would say they
have 3 in series to get a regulated 450V to charge the caps, BUT then
why are the caps only rated at 450V? I've been working on a device that
has an OA2 and an OB2 in series for a regulated 258Vdc. Must be the OB2
is a 108V regulator.
Just my 2 cents to add to the confusion.
Mikek

A thing to be wary of... I got bit by it when I was still a teen...
gas discharge regulator tubes may fail to fire when stored in the dark
for a long time, resulting in too high a voltage applied to
electrolytics with resultant loss of the magic smoke ;-0

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice

Tom Biasi · Nov 15, 2016

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.

Tim Wescott · Nov 15, 2016

On Mon, 14 Nov 2016 13:21:48 -0700, Jim Thompson wrote:

On Mon, 14 Nov 2016 11:44:23 -0800, etpm@whidbey.com wrote:

On Mon, 14 Nov 2016 14:20:02 -0500, Ralph Mowery
rmowery28146@earthlink.net> wrote:

In article <4huj2c9po9e6d9ee1idtcq5nfkv4ncamgm@4ax.com>,
etpm@whidbey.com says...

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

Do you know anythng about electronics at all ? Maybe the solid state
electronics.

The capacitors marked 200 450 mean they are 200 mfd and rated to run at
up to 450 volts on them. They don't have to have that much, just the
maximum.

The 0A2 tubes are like big neon bulbs. The show glow a blue color when
working. You can look up the voltage as I don't want to. Somewhere
around 100 to 150 volts will be required to make them glow. When
glowing they regulate the voltage to that value. Only 2 pins are needed
for them.

You can get an idea of the capacitors if you have an old analog ohm
meter or multimeter. Go to a high ohms scale and see how if the ohms
show very low to start with and after several seconds the ohms should
go to almost an open circuit indication. This will probably have to be
done with atleast one side out of the circuit.

The 5U4 should have a filiment you can see glowing. There are 2 pins
connected to the 2 plates. You should get pulsating DC from each plate
to the ground or common connection point probably where the negative
lead of the capacitors are.
If the capacitors are good or sort of working the DC will be steady.
Thanks for the reply Ralph. Especially the info about the large caps. I
do OK with solid state stuff but tubes are a mystery to me because I
have never really needed to work with them or test them. My son has
googled for a schematic but so far no luck. It may be that he will need
to trace it out himself.
Eric

If it helps your thought processes... pentodes are similar in function
to depletion-mode MOSFETs, triodes likewise, but with lousy LAMBDA ;-)

...Jim Thompson

And thyristors are kinda like SCR's.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

Jim Thompson · Nov 15, 2016

On Mon, 14 Nov 2016 18:32:07 -0600, Tim Wescott
<seemywebsite@myfooter.really> wrote:

On Mon, 14 Nov 2016 13:21:48 -0700, Jim Thompson wrote:

[SNIP]

If it helps your thought processes... pentodes are similar in function
to depletion-mode MOSFETs, triodes likewise, but with lousy LAMBDA ;-)

...Jim Thompson

And thyristors are kinda like SCR's.

Tom Biasi · Nov 15, 2016

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.

Nov 15, 2016

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

Tom Biasi · Nov 15, 2016

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.

Tim Wescott · Nov 15, 2016

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.

--
Tim Wescott
Control systems, embedded software and circuit design
I'm looking for work! See my website if you're interested
http://www.wescottdesign.com

Tom Biasi · Nov 15, 2016

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.

Tim Wescott · Nov 15, 2016

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.

I see your point, though -- some older toob radios have passed through my
hands, and I review and revise the safety measures as necessary.

--
Tim Wescott
Control systems, embedded software and circuit design
I'm looking for work! See my website if you're interested
http://www.wescottdesign.com

default · Nov 16, 2016

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.

Tubes in broken spotwelder & other questions

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