Looking for schematics of QBUS 32KW memory module.

[Jerry Weiss]

On 9/8/19 3:20 PM, Noel Chiappa via cctalk wrote:
>      > From: Mister PDP
>
>      > listed back there were numerous bad addresses all over memory.
>      > ...
>      > I cannot find schematics for any of the boards
>
> .....
>
> With the completed chart in hand, given a failing word (address and bad
> data), you can work out which chip is at fault, and replace it. Repeat
> for all memory errors.
>

Noel's approach is valid and I have done the same on several boards.  
Sorry I don't recognize the vendor of your board.

I would also suggest checking the voltages on the board, especially the 
-5V for the memory chip if the memory faults are scattered across the 
memory space. The circuitry on the upper left of your picture is 
probably a NE555 that is used as a charge pump to generate Vbb from the 
LSI power supplies.

The larger capacitors are probably tantalum (Kemet?) and should have 
aged better than electrolytics of the period.

   Jerry