Mike's PCjr Page

I've been trying to resurrect my PCjr that had the Racore unit in place. It's a long story, but I think I likely damaged the disk drive ribbon cable and am wondering if anyone knows of a place from which to obtain a replacement. When I boot up with all Racore connections intact, the monitor displays the RAM count up to 128K and then shows an "Error A" message, at which point it does nothing else. When I disconnect Racore and use the original disk drive cable, the computer boots up fine. When I swap out the original cable for the Racore one, I get an "Error H" message after the count to 128K. Any thoughts or suggestions would be appreciated.

Please pardon my ignorance, but if there's no way to purchase a cable that would match what came with the Racore unit, is there a way to construct one somehow or determine what's getting in the way of the cable functioning?

Hi Jeff,

I get slammed by work during the week so posts like this wind up getting addressed on weekends. Sometimes weeks late. ;-0

Some questions before we start debugging or worrying about the cable:

• Does your expansion chassis have a memory board? It will be in the top expansion chassis, about 6"x6" and populated with RAM chips lined up in rows. 128K is not correct for a Racore unit; 512 or 640KB is expected.
• Have you looked for broken pins on the sidecar bus connector? (Be sure not to over-tighten the screws. Some Racores were flakey when the screws were too tight.

Can you post a picture of the cable you have? And pictures of the machine so that we can see if all of the necessary cables and boards are present?

Thanks for addressing this Mike. Yes, there is a board in the Racore unit that fits your description. All the pins on the Racore side unit look good. There is a pin that appears pushed in on the side of the jr that the Racore side unit fits into. However, that doesn't seem to get in the way of recognizing the 128 RAM sidecar when I connect that.

When I first tried booting up - after over 30 years of dormancy - the Racore seemed to be recognized (the RAM count showed 384K upon boot-up with no other sidecar attached besides the Racore one). But the disk drive in the jr. didn't seem to be reading any of my disks so I opened things up and disconnected the Racore. I've since gotten a working disk drive for the jr., but the Racore isn't recognized at all and I get the error A message at the 128K count. I assumed - perhaps incorrectly - that the Racore cable could function as the original disk drive cable from the jr., so I tested it without attaching the Racore unit and I got an Error C at boot-up. That's why I suspect that the Racore cable was functional before I disconnected everything but that I may have somehow damaged it. Do you know if that would account for the behavior I'm experiencing now?

I tried attaching the pics but they wouldn't upload due to file size in excess of 2mb.

In a pinch, you can make a new cable from a standard floppy cable and connectors from the old one.

I took a look at pictures that Jeff sent me and the expansion chassis is missing a row of RAM chips, which might be the reason why it is not counting the memory. (If the wrong row is populated DOS will see a hole in the memory and not count further.) The Racore can be configured with partial memory, but the instructions I have posted don't list the valid configurations.

I'll be looking at one of my Racores this weekend to help Jeff out.

FortMax wrote:In a pinch, you can make a new cable from a standard floppy cable and connectors from the old one.

Is that something that's easy to do?

Brutman wrote:I took a look at pictures that Jeff sent me and the expansion chassis is missing a row of RAM chips, which might be the reason why it is not counting the memory. (If the wrong row is populated DOS will see a hole in the memory and not count further.) The Racore can be configured with partial memory, but the instructions I have posted don't list the valid configurations.

I'll be looking at one of my Racores this weekend to help Jeff out.

Thanks very much. Here are the pics (finally got them down to size). It doesn't seem that the RAM chip configuration is the likely culprit as the machine did count up to 384K and was running until I took down the Racore to get at the jr’s disk drive. Once I replaced the drive, it counted up to 128K when booting up and the computer worked - without re-hooking up Racore - using the standard ribbon disk drive cable. It’s only after that tinkering that the count stops at 128K with Racore installed, giving the message Error A. When I remove Racore and try running the computer using the Racore ribbon cable to attach the disk drive to the dd adaptor, the jr won’t run - it counts to 128K and gives the message Error H; that’s what got me thinking that I may have damaged the Racore ribbon and that it may be the issue.

Jeff,

Does your expansion chassis use the pcjr floppy controller or the Racore controller? If its the JR controller cable I believe I have a new one somewhere with my spares.
If I have it and it's what you need I do ask that if the cable doesn't resolve your issue that you return it to me to keep in my bag of tricks.

Thanks,
Sonny

That’s really good of you to offer Sonny. Does the cable you have resemble the one in the picture I posted? I believe it’s what came with the Racore unit. Thanks so much for your response.

- Jeff