31 Jul
2009
31 Jul
'09
1:27 p.m.
Assuming I read you correctly, the mobo appears to have problems.
I really dislike that abreviation. 'System Planar' I can tolerate, but
not that one...
[...]
Besides swapping boards, try removing the socketed
chips (CPU, etc.)
and replacing just those. Or using that CPU in another computer or
board. You have to have something else that runs an 8088 by now, don't
you... >
Alternatively, you could try something that's gone out of fashion now,
but which IMHO is the _only_ way to repair a computer (or for that matter
anything else). And that is to make measurments, deduce what's working
and what's not, and fix the faulty part.
It's already been suggested you get a multimeter (and I'll go along with
that). A logic probe (if you can still find one) is useful too. More
complex and expensive test gear includes an oscilloscope and a logic
analyser. You probably don;t need those at this point.
Try to get the IBM Personal Computer Techncial Reference Manual. It
contains full scheamtics of the motherboard (and in early editions the
I/O boards, these were later moved to the Options and Adapters TechRefs).
This is how I'd attack this problem. Assuming you are prepared to risk
the motherboard on this PSU (and to be honest it's not much of a risk),
conenct the PSU to the motherboard and power up. Using a voltmeter
(voltage rages of a multimeter), check the power voltages at the PSU
connector on the motherboard. If any are missing/wrong then either the
PSU is faulty (and needs repair), or there's a short somwhere on the
motherboard (maybe a decoupling capacitor).
If the votlages are OK there, check them at the power pins of a few ICs.
If they're msisign there, there's an open-circuit on the motherboard.
Now, using the logic probe, check that the CPU clock is present and that
the thing is not being held in the reset state. Check that the address
and data buses arte active (toggling signals).
-tony