PC-9801 Power Resistor

Started by Slypty, 10/15/2018, 10:56 PM

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Slypty

A while ago when I was in Japan, I bought a few of the old school NEC 9801 laptops.  They didn't work, but wanted to try and fix them.  Anyways, I got around to re-capping one of them, and when powering on I get a blue screen only.  The only part I didn't recap, was the power board.  I noticed a damaged power resistor, and left it somewhere before I moved and it has been lost somewhere.

  So I'm left with a partially working PC-9801, the small PCB on the mainboard that has a transformer and a few IC's is missing a power resistor.  So, I bought a cement power resistor rated 5W 22K, now when I power on I blow caps each time.  I think I bought this one because the resistor was a wire wound RJ22, but it was so old I could hardly read it.

  I'm wondering if I should just keep on replacing caps (because a different cap seems to fry each time) or if there's a good starting value for a power resistor.. for instance, you can use a higher resistance than what is regulated but not lower than the needed amount I believe.  So, considering it's a small Power Board, what might be a recommended value to start with?  This is probably too vague, but I have no idea where to start at this point.

NightWolve

Yeah, too vague, but I'd say you need to find a schematic for the power supply or find someone who owns it who can test that resistor and get a value for it.

You should take a photo of the power area too, mark where the resistor was to help the other owner find it, if willing...

Sounds like you did permanent damage to me if you caused new capacitors to pop though, might be a lost cause without a pro EE...