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Help trying to revive an HP Vectra 386s/25

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First post, by L0c0

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Hello everyone,

I received this dusty (literally) Vectra 386s/25 PC with a dead power supply. I tried buying a refurbished supply from apparantely less than reputable sources, both came dead. So I'm trying to rig my own power supply using this pinout: https://pinoutguide.com/Power/hp_725_power_pinout.shtml.

My issue is with this 2pin header sitting on the motherboard. For the life of me I can't figure out what is it for and what voltage should I apply.

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I looked inside the power supply, this connector is isolated from all the rest, and I buzzed the motherboard trying to find which chip is powered by this, no luck there either (was only able to tell that R21 is sitting across both pins).

Hoping that someone could shed some light into this mystery. Thanks.

Reply 1 of 1, by Datadrainer

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This motherboard is unknown to me and there is no clear view of the PSU.
But I recommend to check the voltage rails from an ISA slot to find the correct pinout of the 18-pin connector. The web page of your link is pointing to a 20-pin connector.
In many 386/486 HP Vectra PCs, the PSU is turned on/off by a low voltage line connected to the power switch on the front panel. Maybe that is what P2 is. Check continuity between it and the pins of the front panel ribbon cable connector (blue connector).

Knowing things is great. Understanding things is better. Creating things is even better.

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