I've been working on some H240AS-00 PSUs from the Dell Optiplex 790.
Apparently, it's made by HIPRO.
PCB is labeled Rev. 02
I've been seeing a failure that was reported in this thread.
The 1kV rated ceramic snubber cap (C52) blows and takes Q51, R25, and IC301 with it.
According to stj, who posted in the above thread, this failure can also kill various diodes and resistors around the MOSFET. Thankfully, this hasn't been the case for me yet. I was able to repair a similar H240 by replacing only C52, Q51, R25, and IC301 with parts from a working donor unit. It passed 48 hours of stress testing with Prime95 and is still running.
The original C52 is marked 681K 1KV. I assume I'll need a 680pF cap here. Based on stj's advice, I plan to replace C52 with a 2kV cap like this one on all of my H240s.
IC301 is marked CP012A. According to the posters in this thread, the CP012A is only available from 3rd party Chinese suppliers. I guess I'll be getting these from AliExpress.
Finding a replacement for R25 is the problem for me. It appears to be a .27 ohm resistor. I believe stj described this as a fusible resistor. Unfortunately, I am unable to find a .27 ohm fusible resistor. Does anyone know where I might find a suitable replacement for R25? What kind of power rating do I need?
I'm aware of the bulging output filter caps on the example used in the pictures. I've also included pics of a naked H240 board in case that helps anyone, but the naked board is not from the same PSU.
Apparently, it's made by HIPRO.
PCB is labeled Rev. 02
I've been seeing a failure that was reported in this thread.
The 1kV rated ceramic snubber cap (C52) blows and takes Q51, R25, and IC301 with it.
According to stj, who posted in the above thread, this failure can also kill various diodes and resistors around the MOSFET. Thankfully, this hasn't been the case for me yet. I was able to repair a similar H240 by replacing only C52, Q51, R25, and IC301 with parts from a working donor unit. It passed 48 hours of stress testing with Prime95 and is still running.
The original C52 is marked 681K 1KV. I assume I'll need a 680pF cap here. Based on stj's advice, I plan to replace C52 with a 2kV cap like this one on all of my H240s.
IC301 is marked CP012A. According to the posters in this thread, the CP012A is only available from 3rd party Chinese suppliers. I guess I'll be getting these from AliExpress.
Finding a replacement for R25 is the problem for me. It appears to be a .27 ohm resistor. I believe stj described this as a fusible resistor. Unfortunately, I am unable to find a .27 ohm fusible resistor. Does anyone know where I might find a suitable replacement for R25? What kind of power rating do I need?
I'm aware of the bulging output filter caps on the example used in the pictures. I've also included pics of a naked H240 board in case that helps anyone, but the naked board is not from the same PSU.
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