HI All,
Same friend dropped off a different model of SSI power supply.
This one has a strange fault. No power at all to the NE5560N switch mode chip.
All of the transistors, fuse and caps check out. Though I cant seem to find the fault anywhere.
As far as I can tell, there are no shorts at all on the board. Also fuse does not blow....well it does if I try to measure the MosFet with my DMM.
I have injected a sine and square wave from my function gen through the AC terminals and I also tried DC.
I still cant find where its stopping or why.
I tried another tact. Disconnect the AC line and just power the switch mode NE5560N from my DP832.
That worked. The chip started up and was outputting its sawtooth. That made it all the way to the transistors.
Even stranger, the DC made it all the way to the bulk filter caps. Something that doesn’t work in the opposite direction.
I figured that maybe a diode was faulty but I checked every one in the path.
Though I have no way to test the 800v fast recovery rectifier diodes other the DMM diode mode and one of those Arduino tester things.
For further testing, I was wondering if I could power the NE5560N externally and apply the AC to the input?
I want to see if the rest of the supply is working but I don't want to blow up my DP832.
On that trend, if I cant figure out why the NE5560N isn't getting power, could I rig up a separate supply permanently?
Photos of the supply in question attached. I haven't cleaned the flux off and lost a few pads (not electrically connected, at least on the bottom).
Thanks!