Compaq Proliant 1500 from the mid 90's. The PSU fires up and a green light appears on the backplane, but no POST / no video / nothing on POST card.
The first thing I did was test the pins from the PSU and I see most pins are labelled quite clearly and I have verified all those voltages.
There are 4 pins on the PSU that I don't recognize from their silkscreen labels. I was hoping someone here would know?
Pin labels that I know and check out ok:
"5" = 5.1v
"N5" = -5.0v
"12" = 12.0v
"N12" = -12.0v
"3" = 3.4v
"G" = Ground
Pin labels that I don't recognize:
"3RS" / Pink wire. Reads as 3.8v while PSU is powered but not connected to backplane, and 3.4v when connected.
"5RS" / Red wire. Reads as 5.2v when not connected, 5.1v when connected.
"PG" / White wire. Reads as 5.2v when not connected, 4.8v when connected.
"SD" / Purple wire. Reads as 0v either way.
Other info:
- The server has an actual power switch on the front, not a momentary. I thought one of these might be a standby/soft power but there's no buttons on the case for that.
- The intrusion protection is bypassed (microswitch that interrupts the power at the power switch if the case is open)
- It worked when I stored it
EDIT:
I'm looking through schematics of other power supplies trying to find clues. Here's what I found...
- I suspect PG is "Power Good" or the same as "PWR_OK" on some PSUs. Goes to 5v high when the PSU detects it is providing power within spec.
- 3RS and 5RS could be "Remote Sense" - feedback into the PSU to help it make the PWR_OK decision? Detecting that the power output is as expected? Maybe the motherboard is providing that voltage back so the PSU can adjust to load?
- SD - the only pin that is 'missing' is Standby Power for soft power buttons, but this PSU doesn't have a soft button so I don't think that's it.
The first thing I did was test the pins from the PSU and I see most pins are labelled quite clearly and I have verified all those voltages.
There are 4 pins on the PSU that I don't recognize from their silkscreen labels. I was hoping someone here would know?
Pin labels that I know and check out ok:
"5" = 5.1v
"N5" = -5.0v
"12" = 12.0v
"N12" = -12.0v
"3" = 3.4v
"G" = Ground
Pin labels that I don't recognize:
"3RS" / Pink wire. Reads as 3.8v while PSU is powered but not connected to backplane, and 3.4v when connected.
"5RS" / Red wire. Reads as 5.2v when not connected, 5.1v when connected.
"PG" / White wire. Reads as 5.2v when not connected, 4.8v when connected.
"SD" / Purple wire. Reads as 0v either way.
Other info:
- The server has an actual power switch on the front, not a momentary. I thought one of these might be a standby/soft power but there's no buttons on the case for that.
- The intrusion protection is bypassed (microswitch that interrupts the power at the power switch if the case is open)
- It worked when I stored it
EDIT:
I'm looking through schematics of other power supplies trying to find clues. Here's what I found...
- I suspect PG is "Power Good" or the same as "PWR_OK" on some PSUs. Goes to 5v high when the PSU detects it is providing power within spec.
- 3RS and 5RS could be "Remote Sense" - feedback into the PSU to help it make the PWR_OK decision? Detecting that the power output is as expected? Maybe the motherboard is providing that voltage back so the PSU can adjust to load?
- SD - the only pin that is 'missing' is Standby Power for soft power buttons, but this PSU doesn't have a soft button so I don't think that's it.
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