Mogmeister
New Member
- Messages
- 9
Hi All,
I'm a first time poster and I'm hoping someone might be kind enough to offer help regarding a recently bought (via ebay) 'spares or repair' 150TE that had a wire feed problem.
Initially the welder did nothing on pressing the trigger but I found a broken connection on the torch and replaced that.
Now, when the trigger is pressed the relay makes and the feed wire motor turns but the speed cannot be adjusted. I have tried adjusting the potentiometer on the PCB but it makes no difference to motor speed. I removed the potentiometer from the PCB and tested it off circuit using a multimeter and it is working fine.
From reading other threads, I suspect the faulty component could be the drive transistor and that it is short circuiting? Someone even posted that this is fairly common on hobby Clarkes. From looking at the PCB, I think this is what looks like a medium-power thyristor that I guess it is an SCR? To help with identification, this component is also riveted to a small heat sink.
I understand that SCRs are difficult to test using a multimeter and so my next intended step was to try replacing it to see whether this solves the problem. My difficulty is that there are no markings or lettering on this thyristor and so I did not know what values or spec a replacement thyristor should have. I've had a quick look on Maplin and Farnell websites but that made me no wiser really.
I was hoping that someone might be able to offer some advice on the likely spec for this thyristor so that I could then have a go at changing it.
Any advice you can offer would be greatly received. Cheers.
I'm a first time poster and I'm hoping someone might be kind enough to offer help regarding a recently bought (via ebay) 'spares or repair' 150TE that had a wire feed problem.
Initially the welder did nothing on pressing the trigger but I found a broken connection on the torch and replaced that.
Now, when the trigger is pressed the relay makes and the feed wire motor turns but the speed cannot be adjusted. I have tried adjusting the potentiometer on the PCB but it makes no difference to motor speed. I removed the potentiometer from the PCB and tested it off circuit using a multimeter and it is working fine.
From reading other threads, I suspect the faulty component could be the drive transistor and that it is short circuiting? Someone even posted that this is fairly common on hobby Clarkes. From looking at the PCB, I think this is what looks like a medium-power thyristor that I guess it is an SCR? To help with identification, this component is also riveted to a small heat sink.
I understand that SCRs are difficult to test using a multimeter and so my next intended step was to try replacing it to see whether this solves the problem. My difficulty is that there are no markings or lettering on this thyristor and so I did not know what values or spec a replacement thyristor should have. I've had a quick look on Maplin and Farnell websites but that made me no wiser really.
I was hoping that someone might be able to offer some advice on the likely spec for this thyristor so that I could then have a go at changing it.
Any advice you can offer would be greatly received. Cheers.