Electronics > Repair
Xantrex/Sorensen XHR 40-25 schematic?
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coppercone2:
lol where is waldo

watch that fixes it!
ifonlyeverything:

--- Quote from: NikiG on December 12, 2023, 08:05:43 pm ---Hello, you maybe have problem in two components in corner?

--- End quote ---

Looks a little toasty, I'll have to check it. :) Unfortunately haven't had much time to work on this due to demands of my day job. I also need to order a new set of output capacitors and desolder/individually check the input capacitors and FETs.
coppercone2:
a burned out part is like a really strong guess that it might just work if replaced. and whatever that resistor is connected to also.
NikiG:
 :-+
ifonlyeverything:
4 months later and I finally have a little free time to dick around with this. :) I replaced the capacitor that NikiG identified and fired it up. The relay clicked a bunch of times, the display flickered, the SMPS fired up for a second, and then it went back to flickering the display. I power cycled it a few times. No more relay clicks and the display is flickering. It's not powering up fully as I can't hear the fan run.

I can measure 170V DC across P2 so I know everything upstream is good. U21 (UC3842 SMPS IC) has an unstable VCC-GND voltage, fluctuating between 12V and 13V DC rapidly. I measured the voltage across C38 and I'm getting between 0.8V and 1.0V rather than the expected 18V. I measured the voltage across C35 and I'm seeing 7-8VAC at 60 hz which makes no sense.

This C35 output, I think it's supposed to be 18V, feeds the UC3854 PFC IC and the UC3524 full bridge IC. The UC3842 VREF output feeds the U64 ripple counter, which feeds the UC3524 full bridge IC. I measured this VREF and it's 0.8V to 1V, so nowhere near its intended 5V.

I'm not an expert with SMPS here but I assume something in this UC3842 section is having an issue here. Any suggestions on what I should measure next? I have a scope but I'm a little paranoid of using it since I don't have differential probes.

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