Reviving IBM PC 5150

[SpidersWeb]

Sorry, just generic, mostly by Chicony etc
Only IBM keyboard I have is the PC one for the 5150.

[tezza]

No worries...looking for a genuine one for my IBM AT. Those keyboards are not common!

[SpidersWeb]

Dropped off the 5151 today, and apparently the guy kept an old IBM as a conversation piece.
When I go back to pick it up, I might make sure to ask a few more questions

Felt confident dropping it off, he knew what it was and recognised it, and already has a theory as to what's wrong.
Should hear back in a few days when he gets to it. Left him my Concord XT286 without drives as a test bed but he seemed 50/50 weither he'd even need it or not (think he has quite a few bits out the back).

Trialed my new 5150 board - it looks prestine, genuine IBM RAM chips even, no black dots on any capacitor or (like my XT) legs where capacitors once were. However I can't make it beep. Tested with two PC speakers (both read 8 ohms), and two power supplies (63W original + 200W 386 PSU). Wont initialise my VGA in 8 bit mode but neither did my 5160 (but the XT286 is fine with it) - thought the 5150 might be ok since it has a V20 CPU - will need to see what happens when I get my mono monitor back.

Switches seem correct and I've tried different options for SW1 5&6, but I at least expected beeeeeeeeeeep chirp chirp.

[SpidersWeb]

Just rang repair guy, 5151 is fixed and the display came up fine
Was a single faulty transistor (as he expected when I dropped it off).
$90ish - not bad

So with that gives me a few jobs for the weekend

- run diags ROM on the replcement 5150 board which wont start either

- check ROM on MFM controller isn't faulty (very well could be, as the 386 wont boot off it)
Failing that - replace 41256 chips in 286XT and see if I can get it too boot without parity errors

- play with IBM 5160 PC-XT (unless my CGA card arrives before then, in which case I'll use that and my 1084S).

[SpidersWeb]

Fitted the diagnostics ROM, still nothing, not even beeps, sigh. That ROM needs very little to actually start up.

Started up the 5160 though, used FastLynx to get it's hard drive contents off, then ran Norton Calibrate to do a low level format without losing data. It was taking too long, so I went off to bed. Apparently around 4AM the machine started screeching. Flatmate got up and went down to see if it had a volume control or something but said 'it just stopped'. I found it off but with the power switches all in the ON position.

Anywho now it wont power up until the motherboard is disconnected, so am going to have to dismantle the machine and try if I can see what is wrong. I can't see anything new, but there is a bad cap I will be testing first.

IBM 5151 is working just fine though.

[SpidersWeb]

So the power supply does 11 volts now, umm yey.
And there is 0 ohms on the 12V motherboard line, another sarcastic yey.
Can't see any obvious faults, will be a case of undersoldering, testing, unsoldering, testing etc bah

On the brightside, I moved a few bits to my 286XT which is happily booting with a pair of MFM hard drives running side by side.
Now to find out why it only sees 512K RAM :/

[tezza]

So the power supply does 11 volts now, umm yey.
And there is 0 ohms on the 12V motherboard line, another sarcastic yey.
Can't see any obvious faults, will be a case of undersoldering, testing, unsoldering, testing etc bah

Bugger. Sounds like a short. Probably a cap. I've had to deal with a similar thing myself.