32K PEB card issue hanging DR in FW

[NewcomerTI]

I’ve found out that one of my 32k PEB cards is not functioning and is not seen in the “size” command of Extended Basic. Is the board condition something that can be determined and/or remedied by troubleshooting techniques?  I’m able to swap out one board to the other PEB and it moves the problem.  Any guidance on what to do to help resolve the card acting up would be a big help.  
 

Is there a upgrade/replacement to the 32k board and is it the SAMS card? 

[+Ksarul]

The SAMS card will work as a replacement for a 32K card. There is also an option to add a 32K RAM chip to your Horizon 4000B (the sockets for the chips are present, see the construction manual for what goes there).

 

On troubleshooting older 32K cards, the schematics are available. The CorComp Diagnostic cartridge was designed to test expansion memory, as is the memory tester from @jedimatt42. They will primarily show what part of memory (if anything) is working. It also helps to have an oscilloscope and a PEB extender board to allow you to follow signals through the board. A lot of the time, it is just the buffer chips that have been blown (several 74LS244s and one 74LS245).

[NewcomerTI]

Thanks for the information on the HRD 4000B sockets.  That might be the best solution that I’ll explore for a quick remedy being down one 32k card.
Being without one of those board extenders and needed O-scope (that would make things easier) I might look into replacing the possibly blown buffer chips as a solution to get the card back to a working board.

1 hour ago, Ksarul said:

blown (several 74LS244s and one 74LS245

Thanks for the response.

[+Ksarul]

You might also want to verify that the voltage regulator is good. Do note that on TI-manufactured cards, the heat sink for the regulators is the metal case. Don't run a card for anything much longer than a short life-check test without a temporary heat sink when the case is off.

[Lumpy]

Before changing any internal parts, try cleaning the edge connector contacts. I had one that was not recognized and I cleaned the contacts with a pink pencil eraser and it works fine now.

[NewcomerTI]

On 8/31/2021 at 10:55 PM, Lumpy said:

Before changing any internal parts, try cleaning the edge connector contacts. I had one that was not recognized and I cleaned the contacts with a pink pencil eraser and it works fine now.

So I tried the eraser trick to see if it was some connection problem but it seems that there is a likely failure in one of the other components.  The cards LED does light on power-up. I’m leaning to having bad buffer chips on there that are inhibiting the RAM to be accessed or a bad voltage reg.  Thanks for the suggestions on helping resolve the card.

 

[+Ksarul]

LED says you have +5V, so I would lean towards the buffers as a first possible problem point.

[NewcomerTI]

I have been fortunate in having been provided a memtest program which identified one chip being bad on the 32k mem card.  I replaced the chip and all 32k is functioning on both systems. I also purchased the 32k chip for the HRD 4000B and am pleased to have both working.  Thanks all for the information on how to remedy the problems with the 32k not being operational and in the troubleshooting techniques described above.