A quick comment on the 3325B service manual – Thanks to a kind contributor.
The kernel SA test is a bit flaky on A26U27 PIN 10. This is an inverter output, and can’t be same as the input… correct signature is A70F. Appears to be a misprint in the HP service manual!
In the present case – the culprit was one of the SRAMs, the lower byte. Fortunately, not really a rare part, and easily sourced and replaced, once you know that this is the circuit at fault. You might want to check this very carefully, because there are multiple versions of the 3325A/3325B control boards.