Corcomp 9900 MES - Disk Controller + 32K Board Recreation

[RickyDean]

34 minutes ago, HOME AUTOMATION said:

I have a pile, all from old hard drives.

Understood, I probably do too, somewhere out in deep storage. Getting ready to place a small order to Digikey or Mouser and thought I'd go ahead and get one to see if it fixes my CC  MES. Thanks for responding. I also probably need to change out one of the 22 pin ones  on J2 also, as it appears damaged, though I think it checked out fine when tested 2 years ago.

I think I found them at Digikey, about insulation height .335 inches tall, contact length on post . 126 inches? part # PPPC021LFBN-RC

Edited September 29, 2023 by RickyDean
added content

[RickyDean]

@acadiel any traction on this project? I've replaced the damaged connectors and the unit is still coming up with th Corcomp screen, but the disk and 32k are not being seen. I'm gonna start programming Gal chips to see if I have a bad one. 

[RickyDean]

I decided to burn replacement Gal chip for the upper section. I did one at a time, starting with U11, nothing changed. Then I replaced U10 and it woke up some with Extended basic seeing the 32k when you type in size, but none of the ram testers sees the ram. I tried replacing U9, but no change. 

Then I went into the Corcomp peripherial test and it said that on the 32k test:

"Error Found at Address >2010

Value Written = >2010

Value Read + >2000"

Does this sound like a bad TMS4500, though I've changed it out with two other, believed good, 4500's, or bad dram? Or one of the two 9901's bad?

Edited February 6 by RickyDean
spelling

[RickyDean]

I just tried a HXC emulated disk on the MES and it now accesses the drive but I get a disk not intialized message or an error 16 no disk or dosk drive present. These are known good 40 track disk images.

Edited February 6 by RickyDean
spelling, added content