> > 1) Check the PSU in the 11/34 CPU. It's probably fine,
> > but you don't want to ruin all your boards
>
> How should I check the power supply? I know that many people here
> say you should always do this but with the small cheap micros I've
> picked up so far I haven't bothered.
Disconnect the PSU from the backplanes. Inspect it visually to make
sure there are no obvious uprooted components, cooked tracks, etc.
Connect dummy loads between the important supply rails and ground (I
think they are +5V +15V and -15V in a PDP - Can someone confirm this?
Do you need a load on the 20V rail as well?) and switch on. Measure the
voltages across the dummy loads.
Generally the 15V rails don't need to be loaded very heavily - a
resistor of 100 ohms rated at a few watts ought to do it. You ought to
try and draw several amps from the 5V rail - a 6V car headlamp bulb is
ideal. Light bulbs make good dummy loads in any case because you can
see if there is any current there...
Beyond that, there are plenty of PDP hackers on this list who can take
up the story at this point...
Philip.
PS I too will admit to not doing this nearly often enough...
Received on Tue Feb 17 1998 - 09:09:23 GMT
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