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IBM 5150 not starting up!

C

Chromedome45

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Jul 6, 2009
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Ok so I got a 5150 for testing and evaluation for possible sale.

One problem is it is not starting up. All voltages are within tolerance. Tried the bare minimum test with no boards, set to monochrome SW1 5 & 6 off and no beeps at all. Tried swapping any socketed chips. 8088, 8284A, 8253, 8273 and replaced the 14.318 crystal. Also replaced the 8259A Did not swap RAM.
still no go.

Any ideas on this one guys.
 
With no beeps at all, my first guess would be the CPU.
If that fails, it can't do anything, not even a basic POST, so no beeps.
 
Remove P8 and turn it on to see if it makes any difference.

If that didn't reveal anything, you've probably got one or more bad RAM chips in the first bank.
 
For got to mention I did reseat the ROM chips all 5 of them. I do not have a scope so can't monitor my data or address lines. If DRAM I should get some kind of beep code. I have dead silence.

Stone: you mean P8 like in power connector to motherboard?
 
Sorry Stoner, I guess I misinterpreted the meaning. Anyway I clipped out the old chips and removed the pins that were left. Desoldered the holes and put sockets in the bank 0. Installed 9 64k rams and got the beep tone. Installed rest of chips and running advanced diags on the memory. So far so good. Now to
get a good working B: drive!

Thanks to all for the info. I had totally forgot about the base 16k/64k being so important. A lot of critical stuff gets put in there.
 
Chromedome45 said:
Anyway I clipped out the old chips and removed the pins that were left. Desoldered the holes and put sockets in the bank 0. Installed 9 64k rams and got the beep tone. Installed rest of chips and running advanced diags on the memory. So far so good.
Click to expand...
I have added your motherboard failure to the list at [here].
 
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