Hi all,
I currently have an old German made siegen mig with a wire feed issue.
There is no wire feed with the pot turned down low and as I turn the speed up I only get a slow feed at what should be the fastest.

I have checked the pot which was okay but changed it anyway, all the resistors on the board are fine, I changed one that was a bit low.

I have also changed all of the smaller diodes (with the black marks next to them), apart from the 6A ones located at the bottom of the board.

When the potentiometer is turned down to near 0ohm I get 13.7v at the motor, as soon as I turn the pot up then I get no volatage at the motor. Believe it to be a 24v motor.

Does anyone have any suggestions what to try next.

It arcs fine, and does weld,it’s just the wire feed issue.

To be honest how to check it is a bit beyond me, if it’s what is connected to the small heat sink then it’s (BTA10-400B)

I have ordered a replacement one of these just in case and just waiting for it to arrive

Whilst you're waiting for that part to arrive, it would be a good idea to test the motor.

The motor is working, it’s just getting enough voltage to it that’s the problem!

Okay so it arrived today, swapped it and it’s still not right.

The welder has 5 voltage setting,
Setting 1 gives: 35v on meter (should be 14v)
No2 gives: 30v (should be 15v)
No3 gives: 24v (should be 17.2v)
No4 gives: 28v (should be 18.2v)
No5 gives: 31v (should be 22v)

The higher the setting I choose, the faster the wire speed but all of the adjustment is within the last 1/4 turn of the potentiometer

This is the data panel on the front

Okay so it arrived today, swapped it and it’s still not right.

The welder has 5 voltage setting,
Setting 1 gives: 35v on meter (should be 14v)
No2 gives: 30v (should be 15v)
No3 gives: 24v (should be 17.2v)
No4 gives: 28v (should be 18.2v)
No5 gives: 31v (should be 22v)

The higher the setting I choose, the faster the wire speed but all of the adjustment is within the last 1/4 turn of the potentiometer

Are you welding taking these readings?

Are you welding taking these readings?

No, that’s without pressing the trigger! It almost doubles when I press the trigger but not welding

But the torch isn’t live until I press the trigger!

Is the pot marked xxKA? If so, that's the problem, it's audio/logarithmic taper and the change in resistance speeds up towards the end of travel - what's needed is a linear pot, marked xxKB?
Or the pot could be bad, cheap ones can have a pretty short life, particularly if dust and muck get inside onto the resistor track...
I assume it has been used somewhere dusty and mucky, most welders have...

Dave H. (the other one)

It is a Log potentiometer, that’s what the original was so I replaced it with one of the same, all be it slightly smaller in dimension. It’s a 47KA

On the lower power settings I’m still not getting any voltage to the motor! I’m just baffled now, just thought I’d have a go at getting it running again as it’s value isn’t worth taking in to be repaired!

Are you sure the pot fitted that you swapped out was the original? I would say a bit odd having a log pot in that application

I agree. A log pot can't work in that application. You need a linear sweep to get the control you need . A log pot would be on or off in that circuit, no control. Check the preset pot adjustment too.

Thanks I will order a linear pot and try that. I tried adjusting the smaller pots on the board and they made absolutely no difference to anything!

All sorted now guys thanks,
Seemed to work on the lowest resistance so I canged the 47k pot for a 4.7k linear one and I works..I take it was changed by someone in the past for the wrong value!

Great post I have one of these with exactly the same problem