I have a 386 Prolinea MB that produces a "long-short-short-long-short-short-long-short-short" beep code at POST before video appears. The beeps sort of run together without any obvious pause. The weird thing is, after this, everything progresses as normal. No errors, and boots from a floppy just fine. I even ran Compaq diagnostics and the only "issue" is a missing FPU. I haven't connected a HDD yet. There is absolutely nothing else on the MB except a keyboard, monitor, floppy, and the original SIMM modules.

There's a jumper on the MB to disable onboard video, so I thought I'd try that since this sort of sounds like a video problem beep code, 3 times in a row. That only causes a "long-short-short" and never any video so I switched it back.

The CMOS has been cleared because I have disconnected the external battery I have connected several times. The external battery voltage was around 3.2V, so I tried adding another battery to bring it to 4.7V and no change.

Any ideas? It's clearly complaining about something!

EDIT EDIT EDIT

I thought I'd post this in case anyone wants to know what was wrong, although I doubt many will have the same issue.

I don't have a spare AT power supply so I powered this board from bench power supplies. First I thought +5 is all that would be required, but the MB remained dead until I also supplied +12V, which pulled only 38mA on that voltage.

This morning I decided to also supply the negative voltages to eliminate that and voila, no extraneous beeps! Interestingly, it's only the -12 that does it. I can leave -5 off and it still behaves normally.

So the MB must have a power monitor of some type. I've already looked up a lot of the chips I don't recognize, but there's a PLCC right by the power connector that is branded Compaq and of course there's no info on it.

The RS-232 ports use SN75188 which do not generate their own voltages, so clearly it needs that to operate. Otherwise, no idea what would require -12V on this.