Dell Optiplex 990 psu H240AS-00

[etwallace]

Re: Dell Optiplex 990 psu H240AS-00

Hi Folks,

I know this is an old thread but I thought I'd ask anyway.
My 3010 sff psu has recently died, H240AS-00, its done a few thousand hours, with destroyed C52 (680pf ?), R25 (.27), plus smd R55 (22) and smd D53 (T4 Z9) on the rear. The other components look good but the FET might have failed. If I knew the exact diode I would have a go at repair, but I can't id it from the markings, T4 Z9. Can anyone tell me the exact diode to use please?

ps. Does anyone know the purpose of the black foam sheet between the pcb and the plastic insulator?


Cheers, ETW

[SMDFlea]

Re: Dell Optiplex 990 psu H240AS-00

There`s another old thread about this psu ,https://www.badcaps.net/forum/showthread.php?t=50864
D53 is a 1N4148W ,https://cdn.badcaps-static.com/pdfs/...e7280624d2.pdf

[stj]

Re: Dell Optiplex 990 psu H240AS-00

black foam is to prevent dust building up and causing a short.

[etwallace]

Re: Dell Optiplex 990 psu H240AS-00

Thanks for those replies, very helpful.

Can the psu be switched on, for testing using a resistive load, by connecting to the 4 pin connector (yellow and black wires)?. What connections would be required and can I use a switch or a wire link?

Thanks

[stj]

Re: Dell Optiplex 990 psu H240AS-00

yellow and black are 12v for the cpu!!!
it can be forced on, but i recommend you get a real psu tester - it will have a load resistor etc inside.
https://www.aliexpress.com/item/32864168715.html

[rayfloyd170]

Re: Dell Optiplex 990 psu H240AS-00

Hi sorry to post a problem related to this specific powersupply.

It turns ON for like 2-3 seconds and switches OFF... i opened the unit but i am not sure of what is really the defective part... i have seen 2 components that have visible burning marks and cracked at the dame time.

What is this part? is it a capacitor or varistor? what are the values since i wish to replace them.

[Per Hansson]

Re: Dell Optiplex 990 psu H240AS-00

You do need to do some work yourself.
Just read this thread and the one linked by SMDFlea in post #22 above and you will have your answer in allot more detail than I can provide.

The leadup to the thread linked by SMDFlea is here if you are interested:
https://www.badcaps.net/forum/showth...427#post613427

[rayfloyd170]

Re: Dell Optiplex 990 psu H240AS-00

H240AS-01 version has two identical capacitors at C52 and C11.

Problem is still the same.

Hi may i know the values of C11 and C52? i have similar case

[rayfloyd170]

Re: Dell Optiplex 990 psu H240AS-00

You do need to do some work yourself.
Just read this thread and the one linked by SMDFlea in post #22 above and you will have your answer in allot more detail than I can provide.

The leadup to the thread linked by SMDFlea is here if you are interested:
https://www.badcaps.net/forum/showth...427#post613427

wow, thanks a lot.. i didnt know everything i need is here... very common psu problems

[rayfloyd170]

Re: Dell Optiplex 990 psu H240AS-00

i replaced both c52 and c11 as well as r25 but my problem still the same. psu powers up but after few seconds like 4 seconds it will shut off. something likely tripping it.

what could be the common problem?

[rayfloyd170]

Re: Dell Optiplex 990 psu H240AS-00

i replaced both c52 and c11 as well as r25 but my problem still the same. psu powers up but after few seconds like 4 seconds it will shut off. something likely tripping it.

what could be the common problem?

I think there is no short in my circuit because the fuse is still good... it still powers up after removing the plug from mains and re-inserting it back.

i guess it could be the over or under voltage tripping the psu.. but i just dont know... hope you can help me with this problematic PSU.

[rayfloyd170]

Re: Dell Optiplex 990 psu H240AS-00

any ideas? i replaced both caps already as well as the resistor but still my powersupply will shutdown after a couple of seconds after switching it ON.

[alejandrocastel]

Re: Dell Optiplex 990 psu H240AS-00

Hello everyone, I have a power source from an Optiplex 790, which also burned the surface resistor R55 and the surface diode D53, they were so destroyed that you cannot know the orientation of the diode or the value of the resistance. I appreciate if someone can inform me of this information in order to replace it.
Thank you very much.

[momaka]

Re: Dell Optiplex 990 psu H240AS-00

Hello everyone, I have a power source from an Optiplex 790, which also burned the surface resistor R55 and the surface diode D53, they were so destroyed that you cannot know the orientation of the diode or the value of the resistance. I appreciate if someone can inform me of this information in order to replace it.
Thank you very much.

Posts #21 and #22 contain the answers above.
R55 is 22 Ohms
D53 is apparently a 1N4148W

Again, read the entire thread and also the one linked to in post #22. If you can't find any part number from these two threads, then post back.

[hed190]

Re: Dell Optiplex 990 psu H240AS-00

Hey Guys,

Just to your knowledge, every year i'm getting more of these PSU blown...

Bought some on ebay, but i don't know how much time they will work.

Anyone knows if there's a better version of these PSU?
Mine are:
Model: H240AS-00
DP/N: 3WN11

Regards,
hed190