IBM PC 5150 ROM failures (and substitutes)

[jafir]

How common are ROM failures?

I recently picked up a later 5150 with a 256K motherboard. It had an AST Sixpak Plus and some sort of network/terminal card used when it was in the service of an airline. When I powered it up for the first time, a tantalum capacitor on a floppy drive popped and the power supply shut down. It's C36 here.

I unplugged the drive and that allowed it to power back up again, but of course with a 601 error and it didn't load BASIC. Instead, it had F600 and FC00 ROM errors, exactly like here. This makes me ask if it's pretty common for these to fail. I tried reading one of them, and it showed blank. The other could be read, but didn't match what was here even though the part numbers all matched the C1.10 versions.

I was able to write two replacement MCM68766 EPROMs and the system seems to work flawlessly now, well after replacing the floppy drive with a spare until I can order some capacitors. Also, I removed one of the Motorola EPROM and I replaced it with a Texas Instruments TMS2564, just to see if they really can be used. It worked fine, just the top two legs on each side hanging out of the socket.

 

[modem7]

How common are ROM failures?

To give you some kind of idea, for the IBM PC family, I have recorded some motherboard BIOS ROM failures at [here].
That page excludes Cassette BASIC ROM failures and BIOS expansion ROM failures.
And of course, excluded are failures that members have not reported.

Also, I removed one of the Motorola EPROM and I replaced it with a Texas Instruments TMS2564, just to see if they really can be used. It worked fine, just the top two legs on each side hanging out of the socket.

Thank you. That is useful information. I will give it a go myself.

 

[jafir]

Thanks for compiling that list.

I was surprised that two ROM were bad at the same time, but I guess if the previous users were never using basic, and since the error doesn’t keep from booting, those chips could have failed a decade apart.

 

[modem7]

Also, I removed one of the Motorola EPROM and I replaced it with a Texas Instruments TMS2564, just to see if they really can be used. It worked fine, just the top two legs on each side hanging out of the socket.

Thank you. That is useful information. I will give it a go myself.

I ended up trying this, with some TMS2564's sourced from China.
Photo at [here].
Consequently, I added '2564 EPROM' as a replacement option at [here].