Reviving IBM PC 5150

[SpidersWeb]

Picture of the PSU last weekend, before testing, and before today's cleaning.

[tezza]

Yes, a similar thing happen to me with those square PSU caps and my Lisa Profile drive. I replaced the blown one. There were two more on the board though in hard to get places. I chanced it and reassembled the unit. Within 5 mins another one blew.

Moral of the story. It's probably best to replace ALL of these type of caps at the same time.

[SpidersWeb]

Speaking of caps, I found a 5150/5160 oh noes guide, and did all their resistance tests.

On one line, they said 200-1300 ohms, I had 150ohms and it said to look for bad caps. I found one with a tiny black eye in my memory banks.

Will ignore it for now, but if PSU turns out good and motherboard not responding, I'll replace it, and maybe quite a few more :/
All other resistance tests passed.

[SpidersWeb]

Replaced the other AC filter. Tested PSU with hard disc - runs like a dream with significantly less smoke and it's clean.

Connected to mainboard, no cards, but no beep.
So tested the voltages, they're all within spec (negative rails dead on, positive rails 5% over) and the Power Good was throwing a solid positive signal too.

D1 - a signal diode at the back of the board (that tiny strip behind the ISA slots) is definately gone, and left some of it's sludge on a nearby resistor. Couple of C3 (0.047uF) caps have tiny tiny black dots but they're not shorting enough for the PSU to stop applying power - so I hoped I'd at least get a beep.

Better change that signal diode, and might try randomly moving some of the 4564 RAM chips on top of Bank 0 chips - might get lucky. Worst case I can burn a diagnostic ROM, get an adaptor, and that'll fire up with no memory and output to MDA (which I hope works). Just not feeling terribly excited about replacing 20+ caps for a maybe.

Speaking of which does anyone know if using small ceramic caps (non-polarised, easy to get in 0.047uF, cheap) are fine to use? Everything I read suggests it's ok, but wasn't sure.

Also looked at the ROM BIOS listing in the tech manual PDF, I notice there are BIOS calls for running the cassette. I'm pondering the idea of writing a small prog in MASM to copy GWBasic (etc etc) listings on to tape, so I can run them from the built in BASIC BIOS with CLOAD. BIOS takes care of all the CRC and lead in lead out etc, which makes it pretty easy.

[tezza]

Speaking of which does anyone know if using small ceramic caps (non-polarised, easy to get in 0.047uF, cheap) are fine to use? Everything I read suggests it's ok, but wasn't sure.

Not sure, but I've always replaced tantalum caps with other tantalum ones or (if I couldn't find an equivalent) an electrolytic one.

[SpidersWeb]

Cheers, the fact that something else worked for you gives me a bit more confidence. After replacing the diode, I could easily see myself making a mistake when replacing all the C3 caps - so leaving that as a last resort.

Replaced diode, but appears it's actually for the cassette relays, quite understandable. Old one was definately dead, wouldn't flow anything in either direction and on removal one of it's legs fell off.

Since the PSU isn't suffering from slightly misbehaving caps, I'm thinking memory, but have no way of knowing which of my test chips are actually good lol
I also found doubling up kind of fiddly and worried I'd end up doing more damage than good. So I've ordered the adaptor to allow 27C256 ROM chips, and if I can get a ROM programmer, I'll burn on a diagnostic ROM which can test my memory.

[tezza]

Will this thread help?

http://www.minuszerodegrees.net/5150_51 ... config.htm

Or maybe this one?

http://www.vintage-computer.com/vcforum ... and-Clones

The latter will take a lot of wading through, but in the few years I've been a member of the VCF people are always bringing up 5150 motherboard faults.

[SpidersWeb]

I've done the minuszerodegrees one (that site is epic), and the result was 'most likely BIOS or memory' because the caps aren't shorting enough to kill the PSU output. Using the diagnostic ROM will eliminate or identify these two pretty quick I hope

But yeah I certainlly need to troll that vintage forum some more I think Cheers

[SpidersWeb]

Replacement board, delivered, $132NZD, so tempting :/

[SpidersWeb]

After losing the only ROM burner auction on trademe, I jumped on ebay and bought this:

http://www.ebay.com/itm/ws/eBayISAPI.dl ... true&rt=nc

Has a NEC V20, full RAM populated, pulled from working machine.

Worked out at around $130NZD delivered.

In other news got a large set of cards off trademe for ten bucks. Needed to replace my ESS1868 in the T3200, and in the pile was the exact same sound card - so pretty stoked with that. Also found unopened sealed etc NT4 Workstation packs at my work today - might ask for those - they're Dell OEM though.

[SpidersWeb]

Item has shipped and the seller refunded me $11.50USD in postage, sweeeeeeet.
I just wish some of his other goodies weren't so damn pricey

Anywho this leaves the other board free. If anyone with a ROM burner is mildly interested let me know, otherwise it'll be put in storage. Would be pretty odd for someone to have a near complete 5150 but lacking the mainboard, but thought I'd mention it just in case. Also on that note, I need another case lid, mine has a fair amount of rust. I was attempting to clean it up, but it's definately rust! If I can't find a genuine replacement, I may end up using paint stripper, rust converter, and fresh paint on the metal so it doesn't look like I dragged it home from the tip. I can't sand it down because I'll lose the factory texture, and finding a matching paint colour could be fun too.

In other news, 5160 arrives on Sat, and I may be buying my first house, and the place I'm looking at has a small room that'd be perfect for setting this gear up and maintaining it - fingers crossed.

[SpidersWeb]

Quick update on this. The new board has arrived with the NEC V20 and 256Kb RAM.
However it still in it's static wrap, because setting it up is somewhat pointless until I get the monitor repaired.

I got recommended a place in Newlands, so am going to take it down there and smile.
Going to use the 286XT stripped as a source for them to test with, will have to see how that goes.

In my hunt for XT compat keyboards I have found 1, and accidently aquired 10-15 PS/2 and around 10 5pin AT along the way (bulk lots). So yeah, have a few spare keyboards if anyone gets desperate :/ Still need one more XT keyboard.

[lizardb0y]

Anywho this leaves the other board free. If anyone with a ROM burner is mildly interested let me know, otherwise it'll be put in storage. Would be pretty odd for someone to have a near complete 5150 but lacking the mainboard, but thought I'd mention it just in case.

Do you know if the 5155 luggable uses the same main board as the 5150? I'm looking for a board for my 5155.

[lizardb0y]

Anywho this leaves the other board free. If anyone with a ROM burner is mildly interested let me know, otherwise it'll be put in storage. Would be pretty odd for someone to have a near complete 5150 but lacking the mainboard, but thought I'd mention it just in case.

Do you know if the 5155 luggable uses the same main board as the 5150? I'm looking for a board for my 5155.

Yes, apparently it is exactly the same main board. I'll PM you about it

[tezza]

[quote="SpidersWeb"In my hunt for XT compat keyboards I have found 1, and accidently aquired 10-15 PS/2 and around 10 5pin AT along the way (bulk lots). So yeah, have a few spare keyboards if anyone gets desperate :/ Still need one more XT keyboard.[/quote]

Are the AT keyboards genuine IBM 5170 (IBM AT) keyboards? If so, I'd be interested.