MTPTurbo
Mechanical
- Oct 27, 2005
- 12
(partial schematic)
(full schematic)
Hi all, I've got an old ESAB AC/DC TIG welder that has me scratching my head and I'm hoping some of you more skilled in the art of welder repair can shed some light on my problem. I have placed a couple of links to the scehematic above. The welder was working fine, then abruptly quit providing HF and the arc began wandering wildly..
Here is what info I have:
1) In AC mode everything seems to function normally. If I rotate the polarity switch between positions everything is also ok.
2) In DC mode (STR or REV polarity) there appears to be a short (the welder is under load and the HF circuit quits functioning (shorted out??).
3) The diode between terminals 5 and 19 was bad so I have replaced it with one of the proper polarity and size but the problem remains unchanged.
4) If I disconnect the transformer from the junction at the "top" leg (post 5) of the rectifier everything gets better. Also, If I remove the diode from between terminals 5 and 19 everything gets better (no shorting, HF operation is restored).
5) If I remove any other diode from the rectification circuit it it has no effect on the machine.
6) I have tried disconnecting the capacitor/resistor groups betwwen leads 49 and 50 (welding leads) as well as those between 5 and 21 (rectification circuit) and it has no effect.
7) I can swap the diode from 5 and 19 with the other diode of the same polarity and the machine still behaves the same (it only gets better if I remove the connection betwen the diode and transformer). This tells me the diode isn't the problem.
8) There are no apparent shorts in the machine (no wires/buss bars shorted to one another)
9) All components in the (diodes and SCR's) in the current control circuit appear to be ok (no shorts, etc..)
My assumption may be incorrect, but please help me here. I am thinking that the problem is not in the transformers since everything is ok in AC mode, and that it likely lies in the rectification circuit. I thought I had it figured out when I discovered the bad diode (shorted, had continuity both ways), but it seems to have no impact on the problem.
My question, is the shorted diode a symptom of some other problem, or did it damage some other components that I need to look at?
Any insights would be greatly appreciated.
Thanks,
Chris Spies
(full schematic)
Hi all, I've got an old ESAB AC/DC TIG welder that has me scratching my head and I'm hoping some of you more skilled in the art of welder repair can shed some light on my problem. I have placed a couple of links to the scehematic above. The welder was working fine, then abruptly quit providing HF and the arc began wandering wildly..
Here is what info I have:
1) In AC mode everything seems to function normally. If I rotate the polarity switch between positions everything is also ok.
2) In DC mode (STR or REV polarity) there appears to be a short (the welder is under load and the HF circuit quits functioning (shorted out??).
3) The diode between terminals 5 and 19 was bad so I have replaced it with one of the proper polarity and size but the problem remains unchanged.
4) If I disconnect the transformer from the junction at the "top" leg (post 5) of the rectifier everything gets better. Also, If I remove the diode from between terminals 5 and 19 everything gets better (no shorting, HF operation is restored).
5) If I remove any other diode from the rectification circuit it it has no effect on the machine.
6) I have tried disconnecting the capacitor/resistor groups betwwen leads 49 and 50 (welding leads) as well as those between 5 and 21 (rectification circuit) and it has no effect.
7) I can swap the diode from 5 and 19 with the other diode of the same polarity and the machine still behaves the same (it only gets better if I remove the connection betwen the diode and transformer). This tells me the diode isn't the problem.
8) There are no apparent shorts in the machine (no wires/buss bars shorted to one another)
9) All components in the (diodes and SCR's) in the current control circuit appear to be ok (no shorts, etc..)
My assumption may be incorrect, but please help me here. I am thinking that the problem is not in the transformers since everything is ok in AC mode, and that it likely lies in the rectification circuit. I thought I had it figured out when I discovered the bad diode (shorted, had continuity both ways), but it seems to have no impact on the problem.
My question, is the shorted diode a symptom of some other problem, or did it damage some other components that I need to look at?
Any insights would be greatly appreciated.
Thanks,
Chris Spies
