Captain Chaos
Member
- Joined
- Feb 11, 2022
- Messages
- 21
Hi everyone,
This is my first post, and I'm just getting into the vintage PC repair hobby. I have basic electrical knowledge and some basic equipment like a multimeter and soldering iron. I purchased an IBM PC XT, plus keyboard, monitor and printer. It was being sold as fully working (except the floppy drive), but it has very rapidly deteriorated in various ways and now won't boot at all any more.
It had been fully working days earlier (I was shown days old videos of it in the same location and I think the seller is trustworthy), but when I came to pick it up, the video had stopped working. There is a problem with either the monitor or the MDA card. The monitor just displays a bright green field with a brighter scanline dropping from above. We could tell that it still booted though, as you could press Enter twice for date and time and then enter commands like
Then, while turned off but connected to the wall, the two RIFA capacitors in the power supply blew with a loud bang and a lot of smoke. But even then, the PC would still boot. I decided to purchase the set anyway.
Since then it has deteriorated further, and it now no longer boots at all. The harddrive does spin up and its light flickers very briefly. It seems to get to the POST and then fails with two short beeps. I assume an error code would be showing on screen, but the display doesn't work so we can't tell.
I think it will be a nice challenge to get this thing working again for me and a friend who is helping me. Things we have already done: we have ordered an 8-bit ISA VGA card, so that we can use a VGA monitor and hopefully see what the POST error is, and leave the display problem for later. And we have ordered two 0.1μF 275V X2 filter capacitors to replace the RIFA capacitors.
Hopefully you guys can give us tips and pointers for the following questions/problems we have:
Many thanks in advance for any help you can give us with getting this PC working again! Let me know what information, photos, etc. I can provide to clear things up.
This is my first post, and I'm just getting into the vintage PC repair hobby. I have basic electrical knowledge and some basic equipment like a multimeter and soldering iron. I purchased an IBM PC XT, plus keyboard, monitor and printer. It was being sold as fully working (except the floppy drive), but it has very rapidly deteriorated in various ways and now won't boot at all any more.
It had been fully working days earlier (I was shown days old videos of it in the same location and I think the seller is trustworthy), but when I came to pick it up, the video had stopped working. There is a problem with either the monitor or the MDA card. The monitor just displays a bright green field with a brighter scanline dropping from above. We could tell that it still booted though, as you could press Enter twice for date and time and then enter commands like
dir
which resulted in exactly the harddrive activity one would expect. We could even get the printer to print.Then, while turned off but connected to the wall, the two RIFA capacitors in the power supply blew with a loud bang and a lot of smoke. But even then, the PC would still boot. I decided to purchase the set anyway.
Since then it has deteriorated further, and it now no longer boots at all. The harddrive does spin up and its light flickers very briefly. It seems to get to the POST and then fails with two short beeps. I assume an error code would be showing on screen, but the display doesn't work so we can't tell.
I think it will be a nice challenge to get this thing working again for me and a friend who is helping me. Things we have already done: we have ordered an 8-bit ISA VGA card, so that we can use a VGA monitor and hopefully see what the POST error is, and leave the display problem for later. And we have ordered two 0.1μF 275V X2 filter capacitors to replace the RIFA capacitors.
Hopefully you guys can give us tips and pointers for the following questions/problems we have:
- The C56 and C58 capacitors on the motherboard have been intentionally disabled by someone. Two of their leads have been cut and the capacitors tilted up. Why would this have been done? What problems could it cause? Should we restore/replace them? Since the PC was fully working at one point in this configuration they don't appear to be essential.
- Is the display problem likely to be due to the MDA card, or the monitor? When we remove the card we do get the beeps that indicate it can't initialise the graphics card, so it seems that the BIOS can at least initialise the card. Where do we start to diagnose this?
- The floppy drive turned out to have had its power lead disconnected by someone. When we connect the power, the power supply of the PC won't even turn on (the fan doesn't turn). Does this mean it likely has a short? Where should we start looking to diagnose the floppy drive?
- When we disconnect the harddrive the power supply also will not even turn on. Is this because it needs a minimum load?
Many thanks in advance for any help you can give us with getting this PC working again! Let me know what information, photos, etc. I can provide to clear things up.