HP 110 "garbage" on screen

[Martin Hepperle]

(05-10-2023 08:49 PM)dave-in-kc Wrote:  I replaced those two caps on the display board but don't see any difference. I tested the whole keyboard and attached a photo. I pressed each character 2 times. The numbers and special characters seem to work fine but not the letters.

Any thoughts before I slap it back together?

As already noted above: bit 6 seems to be zero all the time.
All characters that have bit 6==0 are displayed correctly (everything up to the ASCII question mark).

This could be due to a logic chip fault or a broken trace. You could first ring out the path of data bit 6 , and later try to trace signals with an oscilloscope to find out, where the fault enters the chain. It may well be that the bit is never written to the RAM so that the fault lies somewhere upstream, e.g. in the bus drivers/buffers.

Martin