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HP 8116A All Lights and -188.8.8 On Screen

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MarkL:
That's an odd behavior that the display would go out.  The display driver (A3U22, ICM7218A) operates independently from the processor, and the processor would have to tell it to shutdown for the display to go blank.

I would try a couple of things when it gets into this mode:

- Try manually grounding the /RESET signal without powering down the unit.  Depending on which rev of the A3 board you have, you can find /RESET on  header J5 or as a separate probe post, both near the upper edge of the board, and both labeled "RES".  See if that brings it back, albeit temporarily.

- Because U22 operates independently, the display should stay on no matter what else happens.  Check that U22 pin 19 has +5V on it.

Not ignoring the fact that the output dies too, but you have to start somewhere.  The display is an easy thing to tackle first and will likely lead to the issue (or at least one issue if there are multiple).

MarkL:

--- Quote from: mkidd9106 on September 07, 2024, 12:59:11 am ---Hey there, I hope all is well.  I continued to work on the 8116.  After cleaning the CPU board of battery acid from NiCad, I discovered a few faulty components (resistor, diode, and 1858-0053 chip (four transitory chip).
...

--- End quote ---
Exactly which components did you replace and on which board(s)?

In terms of possibilities, it's also not out of the question that the CPU loses its mind after running for a few minutes.  Causes can include EPROM bit-rot and/or intermittent RAM.

Edit: fix typo

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