A2000 R914 resistor (keyboard problem)

[guest11527]

Thanks. It reads, after "jumping" for a while, 14 M ohms. Yes, 14 M ohms. Not 14 K ohms or 14 ohms.

That's more like the resistance of your body, from one hand to another. With that resistance, the keyboard would be completely inoperable, not "half way broken". Hence, your meter did not make contact with the resistor properly. It *does* supply *some* current to the keyboard, after all, and for that, 14 M Ohms is way, way, way, way too large.

[duga]

That's more like the resistance of your body, from one hand to another. With that resistance, the keyboard would be completely inoperable, not "half way broken". Hence, your meter did not make contact with the resistor properly. It *does* supply *some* current to the keyboard, after all, and for that, 14 M Ohms is way, way, way, way too large.

I guess the layer of battery acid on the resistor legs doesn't help. I measured other resistors and they show the correct values.

Expecting new components in a few days.


Edit: in the meantime I removed one 470 ohm resistor that shouldn't exist on a rev 4.5 board (originally rev 4.3) as it is already on the motherboard as R1000 from rev 4.3 and up. Source: https://ftp.fau.de/aminet/docs/hard/Amigafix.txt . Not related to the keyboard issue of course.

[duga]

Fault most probably found. It's on the keyboard. On the circuit board there's a black dot which I presume is short circuiting four lanes. That explains why some keys are working and others not.

The model is:
Mitsumi
KKQ-E96YC
PCB A-2000 (E)

[duga]

"black dot" removed, problably didn't cause any short circuiting. At least the fault is still the same.

Working buttons:
q, w, z, 7, 4, 5, 6, 1, most of the other buttons on the Numpad and a few more.


Can anyone confirm if the 16 leg chip on the circuit board should be 74LS123 as mentioned on http://home.arcor.de/kickstart/TKA/Tutorials/troubleshooter/trouble2.html or HD74HC123AP as on my board? Can they be considered to be the same type of 74 chip?

The mentioned chip + the big MOS chip might have been changed on my board.

[paul1981]

Duga, is this your m/c that you have retrieved from storage? I'm just wondering whether it was working correctly when you purchased it or before it went into storage?

[duga]

It was given to me recently.

[papa_november]

By the way, if R914 fails open, or (in my case) is removed for some inexplicable reason, the 2000 will not boot at all (blank dark screen) if a keyboard is plugged in.