HP-67 failed main board?

[Geoff Quickfall]

Hard to diagnose over the phone (internet :-) but looks like an ACT failure at first glance.

Questions:

1. Is this repeatable or does the display change at every on / off cycle?

2. When keys are pressed, do you see a momentary flicker in the LED display?

3. How are you supplying voltage for testing, regulated bench supply at 3.6v ~ 4v?

4. Are all pins contacting, examine closely at the pin via interface.

That’s to start!