VOGONS


First post, by Alesia

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Hello again, I had the opportunity to pick up a Kaypro 10 locally and I'm trying to get around to troubleshooting it's issues. However I'm really only familiar with 286 and later machines so I could use some guidance of where to look so to speak.

The good news is the Kaypro powers on and the screen can draw it's entire area, evidenced by the flash of markings it makes when the computer is reset. The keyboard also makes ticking sounds when keys are pressed, and the caps lock light illuminates (and never shuts off) so that is working in some capacity.

The bad news is that the Kaypro powers on to a blinking cursor with no splash, beeps, errors, no splash screen, ect and stays there. There is no hard drive activity (I'm assuming it's bad or seized) at any point, however the floppy drive becomes active after a second and never stops running, disks can not be inserted fully either without force. I imaged a CP/M system disk out of curiosity to see if it would read it and got nothing, so no dice there. I did find a capacitor (can see it in one of the below photos) that had it's legs crossed/touching so I straightened that out gently to see if that made a difference and nada.

Aside from the system disk and capacitor, I tried unplugging the data inputs to the system board to see if it would give me any kind of error and that resulted in the same blinking cursor as well. I tried digging around in whatever old troubleshooting threads I could find on google plus the manual and didn't see anything similar to what I am dealing with. If anyone has any idea of where I should be looking, I would appreciate any ideas. Please excuse the dust in the attached photos, I've not gotten in enough to clean the boards and have just been trying to get any signs of function out of the computer. I'm sure I'm missing something obvious, but I'm very out of my wheel house with this computer.

Reply 1 of 4, by Horun

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I see one bad thing and that is the mask tape came off the uv window on the eprom in _154704.jpg. Due to the age of that chip it would not take much light from you (and others before you) to corrupt the bios if not already corrupted.
The contents may still be good but I always get concerned on 40+ year old bios chips missing that mask.
I suggect you check the PSU voltages to make sure they are within 10% of what they should be. Yes the +5v and +12v should be within 5% but if within 10% should still work ok...
All I got on a quick look.

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 2 of 4, by BitWrangler

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You're probably going to have to check a lot of your assumptions, like assuming you've tried a good disk in it yet.

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.

Reply 3 of 4, by Alesia

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Horun wrote on 2024-08-26, 01:17:
I see one bad thing and that is the mask tape came off the uv window on the eprom in _154704.jpg. Due to the age of that chip it […]
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I see one bad thing and that is the mask tape came off the uv window on the eprom in _154704.jpg. Due to the age of that chip it would not take much light from you (and others before you) to corrupt the bios if not already corrupted.
The contents may still be good but I always get concerned on 40+ year old bios chips missing that mask.
I suggect you check the PSU voltages to make sure they are within 10% of what they should be. Yes the +5v and +12v should be within 5% but if within 10% should still work ok...
All I got on a quick look.

Interesting, the mask was long gone by the time I got the machine. I'll put some black masking tape on it when I have it open next to check the voltages, but that being the case, I might have to figure out a replacement if it was intentionally or unintentionally wiped in the past.

Reply 4 of 4, by Alesia

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Thought I would provide an update to this even though it's a pretty big necro at this point.

I got around to testing the power supply voltages and the results were:

+5v rail : 5.10
+12v rail: 11.95
-12v rail: -12.21

I did get the tape mask replaced on the rom as well. I found that Capacitor C4 has a lifted leg (you can actually see it in one of the above pics right below the external ports), so I'm planning to get some long overdue soldering equipment and at least a "cheap" oscilloscope so I can at least check for activity as per the kaypro 10 technical manual. The elephant in the room is of course the hard drive not spinning up, but I don't want to get that deep into the computer until I'm pulling the motherboard to reattach that capacitor leg, at that point I can pull the hard drive pretty easily and see if I can get it going. Given how expensive MFM hard drive replacements/emulators/ect are I want to give it a fair shot before I'm forced to spend hundreds. I did find in some other posts elsewhere that the floppy drive and hard drive spool up together, and that the floppy drive will stay on until the hard drive completes it's initialization and the 10mb ready light is solid, so that could explains that issue I think. I'll still need to get in an service the floppy drive anyways. Hopefully I can update this with good news sooner then later.