Problems with IBM 5150 Power

Chuck Guzis cclist at sydex.com
Mon Jul 27 22:20:01 CDT 2009


On 27 Jul 2009 at 19:03, Joe Giliberti wrote:

> Can anyone suggest what to do next? I have PDFs of the Hardware
> Maintaince manual and the technical service manual.

I assume you're re-seated all of the socketed chips and probed a bit 
with a scope or logic probe to see that the processor is at least 
ticking over--and you've checked your display switch settings.

There are inexpensive POST cards that can display any POST error 
codes, but if you're not even getting a beep, that doesn't sound 
good.

It's not unknown for the old mask-programmed 8Kx8 ROMs to develop bit 
rot. 

If you suspect this, you can either use a 2764-type 28-pin EPROM and 
rig up an adapter to fit the 24-pin socket or pick up some Motorola 
68764 EPROMs and program them and use them directly.  Amazingly, 
during the 5150's heyday, they were near unobtainum, but I've seen 
them offered NOS for something like $6 the each lately.

--Chuck






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