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IBM 5155 faulty memory expansion card

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IBM 5155 faulty memory expansion card

by GJ5155 » Tue Nov 26, 2019 4:54 pm

Hi All,

First post here, thanks Terry.

I picked up an IBM 5155 which did not turn on at all when I first tried. I had preemptively open it up to see if there was anything obviously wrong before powering it on.

Through the process of elimination with everything unplugged and removed, then testing each part I've got it turning on and displaying. But there are some issues I still need to fix.

- When the b:\ floppy drive molex is plugged in the machine fails to turn on at all. Would this be a short maybe? I'm yet to take it out.
- Same issue when the memory expansion is plugged in, it will refuse to turn on. I though it might be a capacitor again, but with basic multimeter none seem to be shorted (like the motherboard one was).

- Capacitor c56 shorted. It had it running for about 20min at first then it just turned off.
- HDD did not work, received error 1701. It's a Hardcard 20, opened it and got the head moving again. And now amazingly it is working fine.

Does anyone have any suggestions on how to test the Memory Expansion card?

I've attached a couple of photo's one of the memory card.

IMG_5102.jpg (199.6 KiB) Viewed 6289 times
IMG_5158.jpg (167.61 KiB) Viewed 6289 times
IMG_5103.jpg (257.7 KiB) Viewed 6289 times
Posts: 5
Joined: Mon Nov 25, 2019 11:21 am

Re: IBM 5155 faulty memory expansion card

by Mark0x01 » Sat Dec 07, 2019 9:56 am

Nice to se another old survivor.

The older hard drives frequently suffer from stiction https://en.wikipedia.org/wiki/Stiction#Hard_disk_drives

A number of quick rotations of the drive in your hand is usually enought to make the platters spin again.
It was a major issue back when drives were about 20Mb, especially in colder weather, where even powering off over a weekend was enough to have a drive failure.

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Joined: Sun Jun 23, 2013 2:11 pm

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