VOGONS


First post, by ITzTravelInTime

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So i got this 64-256k xt motherboard and i want to resurrect it, so i plugged it in with an et4000ax vga card (i have no rgbi compatile monitors for my hercules or ega cards) and i got a screen, but the ram counter during post stops at 064 kb ok and basically the systems hangs from there, i have a post card in one of the isa slots which does not show up post codes because those are unsupported on the xt, but it shows activity on port 80h and so also the cpu, when it comes to 64k on the counter, and it stops writing to port 80h shortly after and it stucks to a value of 0007 most of the times.

So i started swapping parts, i first swapped all the socketed ics on the motherboard because lucly i have some spares for those including a lot of 8088 cpus (but not some working replacement roms and the tools to program those), and ... same beahveour ... so i replaced ram chips multiple times to test all of the compatible ones i have and still the same, i changed vga card and i used a nec v20 and same thing, i also removed ram chips from the vga card to see the problem was the vga card having too mutch of it and no. I have also tried every configuration for the dip switches without luck.

So i am here to ask you for some help thrubble shooting this thing, i have checked all the caps and resistors and they are all fine, also i dont't see any broken traces or damage at a first inspection, but the mobo is an early revision with some patch cables from the factory.

At the end i think that the problem sould be some hidden damage or some bad ics, but i want to hear an opinion from you guys, so let me know if you have any ideas, ecause i am running out of them

Reply 1 of 5, by ITzTravelInTime

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UPDATE: i don't get pc speacker beeps, i get those only if i set the machine to a known failure setting, for example when i set the mobo to use mda but there is no mda card installed

Reply 2 of 5, by jesolo

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Have a look here (specifically under the IBM 5160  (IBM XT) section): http://minuszerodegrees.net
Also verify your jumper settings.
I wish to point out that very few 16-bit VGA cards will work on an IBM XT.

Reply 3 of 5, by ITzTravelInTime

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jesolo wrote:

Have a look here (specifically under the IBM 5160  (IBM XT) section): http://minuszerodegrees.net
Also verify your jumper settings.
I wish to point out that very few 16-bit VGA cards will work on an IBM XT.

I already did all of that and all my vga cards are listed as fully compatible even without the nec v20, but there not any very usefould thrubble shooting tips for my specific situation

Reply 4 of 5, by jesolo

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Have you tested the voltages on all your rails and also your Power Supply under load with a multimeter?? Although the capacitors seems fine, you might have one that is starting to fail.
Alternatively, you can also describe your problem on Vcfed.org under the Forums section.

Reply 5 of 5, by ITzTravelInTime

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the psu is an atx psu with an adapter and it's tested to be fine and also there are no shorts in the mobo, the problem is that on startup the ram counter on the screen stops at 64k