Syncrowave 250 issues

[wojtek077]

I recently acquired syncrowave 250 cc serial number kh470070. I been having issues with R7 running hot especially in AC mode. I measured 1.6amp across the resistor in ac and 800 milliamps in DC mode. I checked the rectifiers sr2 and sr3 with a multimeter both were fine. Also changed the cr2 and cr6 relays thinking that was a issue. I'm planning to change all of them they looked little worn. Also checked the resistance across the transformers they are all fine. I'm lost what it could be. I didn't weld with the machine yet Syncrowave 250 issues
because resistor gets hot quickly don't want to run machine too long.

[Bushytails]

Is your open-circuit voltage normal?

[wojtek077]

Like a across the work and electrode? It's 59.4vdc
50vac in dcen mode and 70.4vac and 1.1vdc in ac mode. So pretty much normal voltage diagram from the technical manual.

[jjohn76]

That's a 100W, 50ohm resistor, so it looks like the RMS amperage is measuring out close (AC seems to be about .2amps high). What is indicating that it is getting too hot? I would expect worse case.for that resistor is open circuit voltage. The current through it would drop when the machine is under load and output voltage is in the 12-36V range.

[wojtek077]

Resistor starts smoking if leave machine on ac with it just idling with panel mode. Don't have a remote padel yet. Interesting, the current drops across the resistor when welding so pretty much safe to weld on it then.