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IBM 5162 - Garbage output on screen?

itsvince725

Experienced Member
Joined
Nov 26, 2016
Messages
444
Location
Pennsylvania
Thanks to forum member Raven I finally have a working video card for my 5162. Fortunately for me it works just fine, outputs nice clear video and text...when I don't try using my DOS 3.2 disk. Putting that in results in the text becoming complete garbage, both on the initial boot screen and in IBM Basic (the disk doesn't get read). What could be causing this?

https://i.imgur.com/Ld8iH5l.jpg

https://i.imgur.com/3UyE9sJ.jpg
 
I'd start by trying a different video card, or try that card in another (known good) machine. My initial thought is bad ram on the video card.
 
Nope! Same behavior without the monochrome card as with it installed. There must be something wrong with the floppy drive. It's a model YD-380 (with no brand name listed) 1.2MB drive made in "1986-44" (44th week of 1986?) and I genuinely don't know how to get to the heads or how to safely disconnect its extremely stuck Molex connector. I already broke a Molex connector off a 5.25 floppy drive once and I'd rather not do it again...
 
That boot floppy is the only 5.25" disk I have on hand so it's the only one I've used.

There must be something wrong with the floppy drive. It's a model YD-380 (with no brand name listed) 1.2MB drive made in "1986-44" (44th week of 1986?) and I genuinely don't know how to get to the heads or how to safely disconnect its extremely stuck Molex connector. I already broke a Molex connector off a 5.25 floppy drive once and I'd rather not do it again...

Hang on a second, you only have a single boot disk that does this, no other disks to try in the machine and no other machines to try that floppy disk in and you jump to "it must be the drive" Sorry to tell you this, but there is simply no way to draw that conclusion based on what you have told us thus far. Also, why jump to the hard thing (broken floppy) and not focus on the easy thing (bad boot disk)?

Get a known good boot disk and try that before taking the machine apart...

What sticks out to me is that you get the same corruption during the BIOS initialization of the VGA card (the purple bit that says something about Oak Technologies). That is a before anything is done with the floppy drive.

At this point we've got no real way to give you direction. It could be the floppy drive (you won't know until you try to boot from a know good boot disk), it could just be the disk (try that one in a known good machine, or try with a known good disk in that machine). But it could just as easily be the power supply running low when the floppy drive kicks in and starving the graphics card of power (try that card in a known good system, or try a known good display card in that system).

And for some future advice, if you seek help online, then a nice clear description of the problem with details on what you have or have not done will not only help you work it out faster, but will allow us to at least try to help you out.
 
I might hit you up for some DOS 5.0 disks, but for now I'm curious about the power supply thing...how exactly would I test it both with and without the floppy drive running to determine if there's a current drain messing up the video card? I can try to get another ISA video card but that wouldn't fix the issue if the problem is the power supply.
 
I can try to get another ISA video card but that wouldn't fix the issue if the problem is the power supply.

It would not, however if it is a known good card, and if it does the same thing in your system, then you'll know it's not the video card.

I'm curious about the power supply thing...how exactly would I test it both with and without the floppy drive running to determine if there's a current drain messing up the video card?

Get a volt meter and measure the voltage coming out of one of the molex connectors and then boot it and see if the voltage fluctuates. You should get a pretty solid 5V from the red wires and 12V from the yellow (well ~4.5 to ~5.5V and ~11.5 to 12.5V). Alternatively you can also push the black (ground) probe into the drive molex, then use the red one to check the voltages at the board by pushing it in the back end of the molex that connects to the board. Look up the color code for an AT power supply to get an idea of what voltages to expect.
 
Alright, I measured the voltages on two separate Molex connectors and they're fine so that narrows things to the boot disk and the video card. That's good it's not the power supply.
 
It's the video card combined with the 5162. Some VGA cards simply don't handle 16-bit writes properly in the 5170 or 5162. Try a different VGA card from a different manufacturer.
 
Okay, I have an update! So here's what's been found so far:

1. The PSU voltages are fine.
2. I picked up an original IBM CGA card yesterday (the green one) and it works fine, no corruption.
3. I made a new DOS boot disk and it too does not boot.

The problem is definitely the floppy drive. Not only does it not read disks properly, it's actually damaging them. Here's what my original boot disk looked like after a few attempts, notice the clear parts where the magnetic material has been worn away:

https://imgur.com/zwgYqjk

Obviously something's not right inside this floppy drive, but then that brings in another problem. While I can free the drive from the case the Molex connector on the back is stuck and stuck tight. I want to completely remove the drive from the machine so I can examine it but I can't do that if I can't disconnect it from the PSU. Is there a safe way to remove these stuck on Molexes without just wiggling it back and forth and hoping it will come loose without breaking the connector off?

Also the machine complains about setup so I need a setup disk. Does the 5162 have its own setup disk or does it just use an AT one?
 
Use needle-nose pliers or forceps to grab the plug and slowly rock it side to side to get it to come out. Make sure you're grabbing the plug and not the socket.

The 5162 uses the 5170 (IBM AT) setup disk. There are ways to set up a system without the setup disk; see www.minuszerodegress.net.
 
Oh, I have 2 boxes of 1.2MB 5.25 disks now so making a setup disk is no big deal. As long as my Windows 98 5.25 floppy maker PC behaves itself.

Does it matter if I use version 2.00 or version 2.07?
 
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