Well, I dug this one out again to finally track down the problem. I tested the suspect traces above and they're good. I also tested the keyboard cable for any broken wires or bad contact, it was good. 5V regulator was still working fine and output was 5V to the vcc pin on the chips. I finally removed all the boards including the motherboard, re-assembled/re-seated everything. Still the 301 keyboard error. I found the manual entry for the 301 error and and it said to "replace the keyboard". As if it were that simple... I suspect there is a bad chip in the keyboard. It's too bad they used such a proprietary internal keyboard connector(6-pin, 12V power) . Not really fixable by me at this point. I'm not expert enough to find the bad chip and replace it, even though many of these old chips can still be ordered online.

I suppose I'll have to keep an eye out for another keyboard. Might take a while though. That about wraps it up for now. I may be getting my hands on a working Apple ][ soon so that might be fun to tinker with in the mean time....

any updates on this?
i have a similar problem

NK

Hi! Digging this old thread. Same issue here. BUT I managed to patch an XT keyboard and it works. There’s is a way to send 5v instead of 12v to the keyboard by doing a small mod to the motherboard.

Wha-hey! You say you've managed to get an XT keyboard working with yours? What exactly was done and could it be done without modifying the motherboard? Perhaps with and in-between voltage regulator or something of the sort?

I don't know what the pinout of the built-in square keyboard connector is, but I suppose given the right pinout, drop the volts down to 5, I guess that's all that's needed essentially?

Cabernut wrote on 2022-09-20, 03:25:

Wha-hey! You say you've managed to get an XT keyboard working with yours? What exactly was done and could it be done without modifying the motherboard? Perhaps with and in-between voltage regulator or something of the sort?

I don't know what the pinout of the built-in square keyboard connector is, but I suppose given the right pinout, drop the volts down to 5, I guess that's all that's needed essentially?

I modified the motherboard. Everything is already there to put a 3 pin header to use a jumper. Only need to cut a trace on the underside.

Soooo... I've dug this old thing out again with renewed vigor to figure out what's wrong with the keyboard. I really would like it to run with original equipment. Its a nice unit, it has the RAM upgrade and an 8087, no HDD but otherwise a nice machine. I'd like to eventually try some old-school ASM or C programming on it. Flip the power switch and squint... still error 301 but still boots into DOS 3.3 off the floppy.

This time, I did some pinout tracing and voltage checking, some probing with an LED probe. What I have so far is that the cable pins check out on both ends, cable connector, 12V, 5V, GND all check out. Nothing physically wrong is apparent. Traces with light spots of corrosion have not affected continuity, cleaned with 99%ipa.

I've spent the better part of a day back-tracing circuits and looking up pinouts and schematics, etc. So far it seems that the 8035 is sending the 301 code since it isn't seeing the key matrix though the sense chips(XR22-908-03A and XR22-950-3B). Key pads trace back to the sense chips, 8035 pins trace to the sense chips pins. Could bad sense chips be causing the 8035 to get confused and throw the 301 code? I'm already in over my head so at this point I can't figure out how to test if the sense chips are bad. There are no schematics for these, or even pinouts for that matter.

I suppose I could swap in some new sense chips, they still seem to be available online, however I do enjoy the process of troubleshooting.