IBM 5160 POST Issue - Memory test repeats

[MikeTwain]

I'm new here so apologies if this is a question I should be looking elsewhere to answer but I searched the forum and did a google search and didn't find any results. Also didn't see anything on Minuszerodegrees

Long story short, I recently purchased a 5160 and I've been trying to repair it. Following the -0 instructions I got to the point of removing the C56 and C58 capacitors due to a short in either the 12v or -12v line. That got me to the point of starting a POST.

However the memory starts counting up to 64k and then stops, the screen then flickers and the test just repeats. It repeats at least 4 times...haven't tried waiting longer.

Any thoughts on what I should do next would be greatly appreciated.

My thought was to start removing ram chips from banks 1-3 and seeing if I got different results but I haven't owned a machine like this in 30 years and I'm a software guy so I'm pretty clueless about hardware.

Thanks in advance!

 

[MikeTwain]

Well Minuszerodegrees turned out to have the answer after all. It turns out that when I set the dip switches to the minimal diagnostic config I didn't realize I was literally setting it to repeat POST mode.

So that question is answered.

I'm now getting a clean boot to ROM BASIC but having trouble with my also recently acquired supposedly XT compatible keyboard. The F1 key works but nothing else

Sorry for the false alarm!

 

[Xarpi]

Hi!

I was having the same issue on my 5160 I talked about in another post
In that time I also acquired a 5155, which is just a portable XT

I swapped the Bios Roms between the 2 machines, and the 5160 posted, while now the 5155 didn't.
Therefore I concluded I had bad Bios Roms on my 5160.

I purchased a new set from a fellow member of this forum and installed them into my 5160.
Its been working great ever since. I'd suggest looking into your ROMS as well, just considering we were having the same issue

Good Luck!

 

[modem7]

I'm new here ...

Welcome to these forums.

Following the -0 instructions I got to the point of removing the C56 and C58 capacitors due to a short in either the 12v or -12v line. That got me to the point of starting a POST.

I have added your C56/C58 'experience' to the list at [here].

However the memory starts counting up to 64k and then stops, the screen then flickers and the test just repeats. It repeats at least 4 times...haven't tried waiting longer.

It turns out that when I set the dip switches to the minimal diagnostic config I didn't realize I was literally setting it to repeat POST mode.

I see. The switch block SW1 photo that I had at [here] showed SW1's switch 1 in the on position. Although the instructions only have the user change switches 5 and 6, I had not catered for users going beyond those switches. I have updated the subject photo to one that has switch 1 in the off position.

Also didn't see anything on Minuszerodegrees

In case someone else with a 5160 sees the same symptom, I have added a 'The POST keeping running in a loop' section to [here].

 

[MikeTwain]

Thanks! I'm super impressed by how much info you have on your site and that you update it as people describe their experiences!