M0110 Keyboard Dead - Ideas?

[GeGnome]

Hi guys,

New member here. Looks like a great forum! Saw a mention of it in JDWs video.

So I recently picked up a few Macintosh Plus machines to repair and rescue and one came with a 128K/512K style keyboard. Unfortunately, using a known good cord, I get no activity from it at all. I cleaned the connector port with the deoxit and confirmed that the cable has continuity on all pins from the Macintosh end through to the PCB.

I don't see anything obviously concerning on the PCB, but considering it was missing a cord when I got it, I wonder if a phone cord had been used and if I've got a fried microcontroller?

I also have a Macintosh Plus keyboard, but the controller is much larger so I can't swap it. This particular M0110 is newer and has a single chip and it's labeled pic1657-824.

So, first are there any specifics that I should check? I did a quick check, and there is continuity across the resistors. I will confirm accurate resistance next, and I will check for a short and the capacitance across that single capacitor before jumping to any conclusions.

Second, if it is a bad I see, are there currently any solutions to this using modern microcontrollers out there? These keyboards are expensive, and it would be a shame to buy another one simply due to a bad chip.

Thank you!

 

[Stephen]

Have you ever confirmed the Macs port? After that - have you confirmed power is making it to the keyboard side when it’s plugged in?

IIRC the outer pins are GND and 5v. Inner two are clock and data. if you have an oscilloscope or logic analyzer it’s trivial to probe clock and data on the keyboard side.

If all else fails, I valiantly offer to buy it from you at a “not working” price

 

[GeGnome]

Have you ever confirmed the Macs port? After that - have you confirmed power is making it to the keyboard side when it’s plugged in?

IIRC the outer pins are GND and 5v. Inner two are clock and data. if you have an oscilloscope or logic analyzer it’s trivial to probe clock and data on the keyboard side.

If all else fails, I valiantly offer to buy it from you at a “not working” price

Yes, this Mac works fine with my proper Macintosh Plus keyboard and cable. As soon as I plug that cable in to this particular keyboard and Boot It up it will not function.

I have confirmed that the Mac side of the cable shows continuity with components such as resistors on the PCB. I actually recently bought a new oscilloscope and logic probe, but have not used them yet. I suppose it's a good time to pull them out and learn!

I will certainly keep you in mind if I decide to sell it. Unfortunately I have $35 just tied up into the space bar that I purchased for this thing before I knew that it was dead! Seems that there has to be a way to use a modern microcontroller with decoding software on it if all else fails.

Thanks for the tips, I'll be sure to follow up.

 

[lilliputian]

Possible that the controller chip in the keyboard was blown at some point...

 

[RetroTheory]

There are caps that can fail inside the keyboard too, and components that can corrode

 

[GeGnome]

There are caps that can fail inside the keyboard too, and components that can corrode

Wow that one does have corrosion! Mine looks clean and there seems to be continuity, but I'm going to carefully check the values and all the resistors and the capacitor before assuming that it's the controller chip.

 

[GeGnome]

UPDATE! I connected the keyboard again today and it was working! Well...mostly.

On two occasions, on two different macs, it did stop working but then it resumed functioning after a reboot.

I used deoxit on the port and it cleaned up nicely, as well as the chip socket, but I suspect that there is a connection issue due to oxidation as suggested above. I checked and recorded all the voltages on all components while it was working in case I need to do troubleshooting in the future. I will also plan to record data with a logic probe or my oscilloscope when I get some time.

Since a mask EPROM shouldn't be intermittently good, I think it's safe to say that the chip is good! (Right???)

This keyboard needs a complete disassembly and cleaning, so I will address any corrosion, reflow solder joints and check all the components carefully (resistor values, capacitance etc). I think it also makes sense to put new caps on it... Or at least the black one that appears to be an electrolytic.

Thanks for the help! I will post an update if anything interesting comes about.

 

[pyranger]

congrats on your working keyboard. I have the same 1986 version, with the PIC1657 uC. My keyboard isn't working. I used an oscope to confirm the motherboard was sending pulses on the dataline. however, the keyboard didn't send any clock pulses. Probing the PIC1657 shows sine type waves (about 7MHz I seem to remember) on a couple of pins close to the end of the IC so the oscillator seems to be functioning. But that's about it.

Does anyone know of a source for replacement ICs or perhaps the FW to reprogram a new IC?

How about a modern replacement? I've seen some USB or PS2 solutions nothing that inputs the keyboard matrix and outputs the apple 2 wire protocol.

thanks in advance for any suggestions.