Electronics > Repair
HP 3468A does not complete self-test, the LCD display all on.
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cruff:
Can you unsolder and lift one or more of the D7-D0 input pins to the 373 and see if those signals clear up?
fenugrec:
+1, either the source of those signals is defective, or something else on the bus is affecting them. I think you're close.
StrayElectrons:
Lifting a pin I didn't thought of that!   Thank you, certainly I'll try that, but it isn't socketed, have to cut a leg.

Yes, I meant the inputs and outputs of this '373 are garbage.   Enable pin is clean.   The CD4076 in and outputs are clean.  And other than processor's D0-D7 are clean signals.

Cheers,
StrayElectrons:
I'm still on trouble shooting.

The microcontroller is outputting bad quality signals,    Slow rise to high but on turn off going low is sharp and nice.

Does this HP3486A's microcontroller processor contains small ROM or just ram only?     Can I use intel 8039 or must I find a MK36000 microcontroller?   Which I cannot find MK36000 anymore on ebay.

Cheers,
fenugrec:

--- Quote from: StrayElectrons on December 22, 2024, 08:58:41 pm ---Does this HP3486A's microcontroller processor contains small ROM or just ram only?     Can I use intel 8039 or must I find a MK36000 microcontroller?
--- End quote ---

Hm, isn't MK36000 simply an EPROM ? In any case, the 8039 (also used in the 3478A which I have worked extensively on) has no built-in ROM or customization.
If you have an EPROM reader I recommend you (carefully) make a backup of the ROM chip, I don't know if anyone has dumped it yet, and the 3478A is too different to have compatible firmware.
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