Dell H235P-00 recap

[lucky13]

After a power outage, Dell Optiplex 760 won't start. Power LED flashing amber.

Suspect bad caps.

Crack open the power supply, and sure enough. there are.

C60 2200/10V > 2200/16V (Old cap measured 22uF & ESR 4.1)
C107 2200/16V LPZ > 2200/16V (Old cap measured 2244uF & ESR 0.01) <Wow
C114 680/16V > 1000/16V (Old cap measured 2uF & ESR 13.4)
C119 2200/10V > 2200/16V (Old cap measured 333uF & ESR 1.61)

On small board for fan, 100/25V > 2*47/25V (Old cap measured 0uF, ESR 30). I don't have any 100uF on hand so I twsited two 47uF together and soldered it in.

Computer is back up and running.

Hope this helps someone in the future.

[Wester547]

Re: Dell H235P-00 recap

Were any of them bulging? Sounds like the bad caps were failed LTEC LZP and TK (or possibly LXY and ST). Maybe some Teapo SC, SEK, or SS thrown into the mix, or OST RLP or RLS? It almost sounds like one of them was actually in spec. Was it deformed?

EDIT: It's true that such a low ESR reading and a higher-than-nominal-capacitance reading is indicative of high leakage current (either the electrolyte is attacking the aluminum oxide or it can no longer repair defects in the dielectric because it's starting to break down), unless it was an ultra low ESR capacitor but you don't find those in PSUs usually.

[stj]

Re: Dell H235P-00 recap

none are in spec, the 0.01 esr one is almost 100% leaky if you have a tester that shows leakage.

i have seen it myself, leakage goes up and sometimes the uf too! and esr goes down.

[lucky13]

Re: Dell H235P-00 recap

OK, here are some pictures.

The small cap on the fan PCB is C818.

I missed one on the list. I did not see the printing on the PCB. It is the 1500u (3rd one from the line up) that is not deformed. I replaced it with 1500u/16V FM.

[Wester547]

Re: Dell H235P-00 recap

Okay, bulged LZGs, LZPs, and LXYs. The bastards - they used Rubycon in all the low stress positions and LTEC in the critical, higher stress positions. That looks like it might be an ADDA or Sunon fan. I hope it still works (it might need lubrication).

[kc8adu]

Re: Dell H235P-00 recap

built in failure points.the caps and the "death adda" fan.

[lucky13]

Re: Dell H235P-00 recap

Hmm.. fan seems to be running fine with no strange noise. I need to research this "death adda" fan syndrome and get a replacement ready.

[mitchw]

Re: Dell H235P-00 recap

Hi, I am repairing the same PSU and despite changing all of the capacitors (even the main smoothing filter that was the main problem), I still get blinking orange light. All of them were bad, only the Nichicon ones tested good, go figure

I noticed that the resistor R844 is crusty and it is measuring 180 ohms. This seems rather high. I used the cropped image from OP as my resistor has almost unrecognisable color bands.

As far I decoded it, it seems that it could be 1 ohms 2%?

Can someone decode the image and what resistor should I use? Or perhaps if someone has schematics for this thing

Thanks

[mitchw]

Re: Dell H235P-00 recap

Nevermind, I think the 180 ohms is correct value.

It is now working. Like I said, it needed a full recap including all of the small value capacitors (e.g. 22uF 16V, etc.).

Main problem was open main/PFC capacitor (420V 150uF) and shorted PFC rectifier (10A 600V TO220), most likely blown because of open main capacitor.

[fildelo]

Re: Dell H235P-00 recap

This thread is still useful in august 2019.
You made me want to repair my H235P-00 which only provided 1V on green PS-ON.
I had 320Vcc on the 420V/150uF. I did'nt change it.
I only replaced the bulged capacitors (3x 2200uF, 2x 1500 and 1x 680uF) and everything works again.
Thanks from France

[Raziel19935]

Re: Dell H235P-00 recap

hi i have 2 units of these, the mosfets and resistors are good (measured with the multimeter), there is no 5v in green, it is the h255e-01, has anyone encountered this problem?