Compaq Pentium I not booting. \ VOGONS

Compaq Pentium I not booting.

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First post, by T4600C

Posted on 2015-09-20, 12:45

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I have a Compaq Presario 7212 (Or Compaq Presario 7210 ) AT style motherboard with a Pentium I that I was installing a secondary harddrive into.
Everything was working until that point, it passed every Norton Utility and Compaq diagnostic test.
The system was running while I was looking at some connectors, I accidentally kicked the harddrive cradle, moving it along its rail slightly and then everything shut down. The power supply was making a weird high pitched noise, as if water was boiling, for a short moment. I'm not smelling anything burning inside the powersupply or on the motherboard.

Now the board no longer wants to boot. The only things that turn on for a moment are the keyboard lights.
The harddrives still do their thing when I turn on the power, the harddrive light from the motherboard even lights up. But the 'power on' light from the motherboard does NOT. My screen does not get any signal either.

I have re-inserted every powersupply connector. I have put back the original 2 4MB EDO ram simms supplied by compaq. I disconnected the harddrives, floppy drives and tried different configurations. I switched out the Pentium I CPU for an other Pentium I. Tried a PCI video card.

None of that has worked, what should I try next?

Thanks for reading.

Reply 1 of 10, by alexanrs

Posted on 2015-09-20, 13:52

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Is the PSU connector propertary? Have you tried another PSU?

Reply 2 of 10, by brostenen

Posted on 2015-09-20, 13:54

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Somehow it sounds like a dead motherboard to me.
You could test the cpu on an SS7 if the cpu is supported by that.
You could try testing another PSU on that Compaq as well.
Try testing as much different parts in different systems as possible.

The worst thing could be that both MOBO and the PSU are dead.

Don't eat stuff off a 15 year old never cleaned cpu cooler.
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Reply 3 of 10, by PeterLI

Posted on 2015-09-20, 13:56

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You probably killed it unintentionally. It happens. 😈

Reply 4 of 10, by Sutekh94

Posted on 2015-09-20, 13:57

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brostenen wrote:
The worst thing could be that both MOBO and the PSU are dead.

And, if I know Compaq systems like I do, the motherboard is more than likely going to be proprietary, not AT style. I'd say try another PSU in that system if possible. If it turns out that the mobo is dead, good luck finding a replacement...

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Reply 5 of 10, by T4600C

Posted on 2015-09-20, 14:47

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If anyone has a schematic of this board: https://www.dropbox.com/s/nyaodfpsgkp8r45/FOTO0860.JPG?dl=0
Then maybe I could buy a multimeter and test everything. If anything has been damanged by the cradle movement, which parts would it be?

Reply 6 of 10, by shamino

Posted on 2015-09-20, 15:43

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Sounds to me like something short circuited and overloaded the PSU, possibly damaging it. It might have shorted on the hard drive PCB, not necessarily the motherboard.
You could test for shorts at the board's and drive's power connectors, but from your description it sounds like the PSU is able to start up now, so it seems the short is no longer there.
You could measure output voltages also, see if they look reasonable. Preferably do that while it's hooked up to a load and trying to run. +5v and +12v can be tested at a molex connector.
You could try swapping PSU with same motherboard, and motherboard with same PSU (but consider possibility the PSU might damage other boards if it's really messed up).
That appears to be an LPX form factor motherboard. I don't know how consistently they can replace each other and fit correctly, never tried.

Reply 7 of 10, by ODwilly

Posted on 2015-09-21, 11:36

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When you power it on does your powersupply still make the squealing noise? I once had a bad AT powersupply that blew out and sounded like that as well. Try another AT psu first is my suggestion (make sure the pinout is not proprietary)

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Reply 8 of 10, by T4600C

Posted on 2015-09-21, 21:46

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ODwilly wrote:
When you power it on does your powersupply still make the squealing noise? I once had a bad AT powersupply that blew out and sounded like that as well. Try another AT psu first is my suggestion (make sure the pinout is not proprietary)

I don't have an other AT powersupply, or AT compatible motherboard. The PSU is no longer making the squealing noise.

Is it possible to modify an ATX PSU to connect to P8 and P9 ports?

Reply 9 of 10, by brostenen

Posted on 2015-09-21, 22:02

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T4600C wrote:

I don't have an other AT powersupply, or AT compatible motherboard. The PSU is no longer making the squealing noise.

Is it possible to modify an ATX PSU to connect to P8 and P9 ports?

Absolutely. Just a matter of connecting the right voltage to the right pin's.
For the power on, just use the original switch, as an ATX psu will power up when the green wire is connected to a black (ground).

This is a project that I need to do my self. I have maby 8 of these in a box somewhere.

And if I butcher some dead AT psu or ATX for the P10, then I could get two extra ones, if they can be used as P8 and P9.

Don't eat stuff off a 15 year old never cleaned cpu cooler.
Those cakes make you sick....

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Reply 10 of 10, by ODwilly

Posted on 2015-09-24, 06:10

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You can buy an ATX to AT conversion cable on ebay for $12

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