Seasonic not giving PG: safe to apply 5 V?

[Behemot]

I got two Seasonic OEMs with no power good signal. The 400W I've just jumpered to +5 V and left in bitcoin miner. Recapped ofc first, it works with no problems for two weeks now, 24/7.

The other, 500W, I tried to repair by swapping the daughterboard with secondary IC (from my dead old Seasonic) which shoudl give the PG signal. They are the same and mine should be working with 99,9% chance. But no change.

Initially I found one SMD resistor torn off the main PCB so I soldered it back. Was not sure with the soldering so I changed it for small ordinary axial resistor (same value - 100 ohms) but still nothing. So am thinking about just leaving it be as it most likely otherwise works normaly as long as I apply +5 V to the power good for MB to turn on.

So I am just thinking, is it safe in long-term? Well, the PSU could go bad, but the PG should not matter for that because if it goes over/under votlage, it should shut down the PSU itself, so no problem if it won't shut down MB fist, right? It does not have any means of OCP/OPP so this won't matter as well. And if I'll recap the PSU, what chance it even is there for it to go bad?

[LDSisHere]

Re: Seasonic not giving PG: safe to apply 5 V?

Can you find a datasheet for the supervisor chip?

[Behemot]

Re: Seasonic not giving PG: safe to apply 5 V?

HY-510N. I found nothing wrong anywhere in the compensation so I really don't know why it does not work. All diodes are good, all resistors are good, all transistors are good (or at least are not shorted).

[LDSisHere]

Re: Seasonic not giving PG: safe to apply 5 V?

A few months ago I repaired a supply that had a problem similar to yours. The PGI voltage was not what it should have been but I could not find any shorted / open part. It turned out to be a diode that would pass the DMM diode test but had an out of circuit resistance of approximately 30k ohms.

I would suggest seeing if your PGI voltage is in spec or not. I hope this helps you resolve your issue.

[Behemot]

Re: Seasonic not giving PG: safe to apply 5 V?

Well when I measured some pins on both the daughterboards out of main board, there were some differences. But most of the diodes is on the DB itself and I have swapped the whole boards, not just the monitors. And it still does not work so…

[Behemot]

Re: Seasonic not giving PG: safe to apply 5 V?

With PG and +5 V jumpered, one burned rectifier on +12 V (no worries, there are another two ) and one strange behavior. When unjumpered, 32 A output on +12 V without problems and with +-50 mV ripple.

I think I will solder the PG cable directly into +5 V, as such it should not have any connection with the monitor so it won't be driving it mad. But such PSU is not really that safe to be sold so I'll keep it into bitcoin miner when I'll upgrade next time, I'll need more powerfull PSU anyway (for 3 graphics).