Power Good timing question

[jamesbo]

I have an old ISO-400 PSU that I recently took out of service. I opened it up and there was one Fuhjyyu 1000uf 16V cap bulging, I replaced it with a Rubycon MCZ. All the other caps look ok. When I test it with a Coolmax PSU tester, all the voltage are correct. The first time I test it the Power Good is 480ms. When I test again right afterwards, I get a Power Good timing High. It works fine in service. I checked a number of articles on the web and the only place I find a tolerance for the PG timing is related to the the Coolmax Tester. Is the timing issue normal or should I examine it further? The PSU has a number of Fuhjyyu and Teapo capacitors. I'm keeping the supply as a spare for some of the old computers I am maintaining for my family, simple internet/business machines with onboard graphics.

[c_hegge]

Re: Power Good timing question

I wouldn't worry. It's usually because it was one of the last pins to make contact with the tester. I would always plug it in to the tester before connecting it to the mains, and it would never happen.

[jamesbo]

Re: Power Good timing question

Thanks much.

[momaka]

Re: Power Good timing question

I wouldn't worry.

I agree.
However, I would strongly advise that you change the Fuhjyyu caps. The fact that one Fuhjyyu is failed means the others may not be far behind.
Overall, the PSU may be okay if you just want to use it to test a PC for a few minutes. Any longer than that and you may be doing damage to the components in that computer.

Also, Rubycon MCZ is not really a suitable replacement for PSU caps. You need something with a little higher ESR than that. Rubycon YXG and ZL, Panasonic FC, FR, and FM, Nichicon PM, PW, and HE, United Chemicon LXY, LXZ, KY, and KZE, and Samxon RS are all better choices.

With that said, the Rubycon MCZ you installed is still a better option than leaving the bad cap in the PSU.

[PCBONEZ]

Re: Power Good timing question

I have an old ISO-400 PSU that I recently took out of service. I opened it up and there was one Fuhjyyu 1000uf 16V cap bulging, I replaced it with a Rubycon MCZ. All the other caps look ok. When I test it with a Coolmax PSU tester, all the voltage are correct. The first time I test it the Power Good is 480ms. When I test again right afterwards, I get a Power Good timing High. It works fine in service. I checked a number of articles on the web and the only place I find a tolerance for the PG timing is related to the the Coolmax Tester. Is the timing issue normal or should I examine it further? The PSU has a number of Fuhjyyu and Teapo capacitors. I'm keeping the supply as a spare for some of the old computers I am maintaining for my family, simple internet/business machines with onboard graphics.

It's in Intel specifications somewhere.
I think in the docs for VRMs.
Haven't read it for a while.
.

[PCBONEZ]

Re: Power Good timing question


Section 3.3.
The ATX spec 2.1 refers you back to this one for the timings.

Intel and these guys verbatim repeat each other on the topic.
Not sure which actually originated it.
.

[jamesbo]

Re: Power Good timing question

I finished replacing all the caps with Panasonic FM & FC, except for the 2 power caps. Now the Power Good timing is 490-500ms everytime.