British Columbia Technical Repair Assistance on a KDF11-B

[NeXT]

I have a board here that I was given by another forum member about a decade ago which ran fine for years until one day it didn't come back after a power cycle. After verifying jumpers, baselining the board and exhausting my ability to test QBUS machines and available local resources I've determined that something on the CPU board itself like a buffer is partially corrupting or hanging the data bus and forcing the CPU to halt for everything to the point it won't even reach an ODT prompt. Swapping socketed parts with a donor board ruled out the major chipsets and bootstrap ROM.
I'm looking for someone offering to take the board on and find out what the fault is. Printsets and schematics are available.

 

[jmdhuse]

Hello NeXT,

I recently bought 4 kdf11-b boards from Ebay that were sold as "non-functional, for parts". They did not have boot ROMs or the processors chips in them. I put CPU/MMU/FPU chips into them from KDF11-A boards that I had, installed boot ROMs, and went to work. I have been able to bring three of them back to life, as indicated by their ability to repeatedly boot into XXDP from a floppy drive and run the JKL5B0 diagnostic with all pertinent tests enabled for hours without fail.

I can't promise anything, but it would be good to put the knowledge I've gained to use, rather than forgetting it all!

Let me know if you'd like me to take a crack at it...

Regards, Jon.

 

[NeXT]

Alright sure. By chance where are you located as well?

 

[jmdhuse]

Alright sure. By chance where are you located as well?

I'm on the same continent, but not too close... Chandler Arizona USA (Phoenix metro area).