Syncrowave 250 full amperage output KB057067

[mewanchyna]

After I verified operation of each portion of the board such as AC timing reference, switching, etc, the welder was still exhibiting strange behavior. Using a stick welding, I would set the current very low. Once I struck an arc, the current rose dramatically. After some additional checking through...

[mewanchyna]

Thanks Jon,
I found that RC55 pin 4.

For those cheap op amps, I decided to cut off legs rather than heat and reheat the pads and risk lifting pads and tracks. Thankfully, there are no microcontrollers on this board.

[mewanchyna]

Hi Jon,
I did scope the drive signals from A4 pin 7 and A5 pin 7 which drive the transistors that drive the primary of the drive transformers for the SCR pairs. (no ground loop as the secondary is completely isolated). As I change the amperage control on the front panel, the pulse width changes,...

[mewanchyna]

Hi All, After doing some strategic part replacement, I have tested most portions of the circuit and portions of the circuit seem to work as expected. Unfortunately, the manual gives little information as to calibration, which I think may be another problem. I think the potentiometer, which I think is...

[mewanchyna]

So don't breath or light a match. Did I mention that I hated Chemistry in school. ...

[mewanchyna]

Actually, I think it is Chlorine gas and NaOH. Nice combination. In any case, something to do outside....

[mewanchyna]

I haven't put my scope on the gate drive signals yet. I checked all voltages from front panel controls and switches. They all check out fine, including the current adjustment potentiometer.

From the schematic, the feedback voltage from the shunt goes into one op amp and is sent to the control...

[mewanchyna]

No Hall device on this year. Shunt resistor instead. Nevertheless, thanks for responding. I was starting to feel very alone on this group.

[mewanchyna]

I am trying to fix a 1991 Syncrowave 250. It has no amperage control. The welder was working and suddenly, went full output. I am quite competent in electronics and repairs and need a few hints as to the operation of the control board (135254). I am aware of the fact that the PCB common is NOT at chassis...