8 Sep
2019
8 Sep
'19
2:01 p.m.
On 9/8/19 3:20 PM, Noel Chiappa via cctalk wrote:
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
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.