Duo 280c ADB Woes

[sutekh]

Been a while since I posted, but I picked up a Duo Dock at a warehouse sale this week and it's got me scratching that old 68K itch again The dock came with a very basic 210 (lowest end Duo, small drive, limited RAM) that works fine, and as luck would have it, the dock has been upgraded to the later lid that accommodates color duos!

That's where my luck ran dry though :/ I plugged in my 280c, which boots up fine, but the ADB attached keyboard and mouse don't work. Huh... I cleaned connectors, tried reseating a few times etc. to no avail. Just to rule out the Duo Dock, I then pulled out my minidock and an etherdock. No working ADB there either. I loaded up a couple of ADB utils from Mac Garden and regardless of the dock or keyboard I try (several of each at this point), the 280c never detects them.

To be honest, I'm not sure I've ever tried connecting an ADB keyboard to this laptop before, so it could have been inop for decades. It does definitely output 5v though, because I've used the ADB port to power accessories. Before I go down the dock connector pinout electrical troubleshooting rabbit hole, I'm wondering if anyone has ever experienced similar behavior from a Duo?

 

[finkmac]

before anything else... have you recapped the 280c? it 100% needs all the lytic capacitors on the mainboard and LCD panel replaced.

 

[sutekh]

before anything else... have you recapped the 280c? it 100% needs all the lytic capacitors on the mainboard and LCD panel replaced.

I fully recapped it a couple of years ago. Thankfully, none had been leaking significantly and the boards are all in great shape!

I seem to recall that ADB on the Duo is somehow intertwined with the modem daughter board via the power manager... I have a basic power switch board from a non-modem Duo I may try to swap in and see what happens as a next step. It's been too long since I futzed with these and I've forgotten some of their peculiarities!

 

[Arbee]

ADB on the Duos is a little weird. On the 280c the keyboard is a bare matrix keyboard like the Apple IIe and the trackball is a quadrature device, like an M0100 mouse. The Power Manager microcontroller emulates ADB devices for both of them, but it also has a pin to communicate with a standard ADB bus too. (And it's hardware-accelerated ADB, which wasn't used in any other Macs).

Anyway, I would guess a bad connection somewhere. The hardware note for the original Duo 210/230 has the pinout for the dock connector, so I'd start with seeing if there's continuity from the ADB line there back to the Power Manager.

 

[jmacz]

To be honest, I'm not sure I've ever tried connecting an ADB keyboard to this laptop before, so it could have been inop for decades. It does definitely output 5v though, because I've used the ADB port to power accessories. Before I go down the dock connector pinout electrical troubleshooting rabbit hole, I'm wondering if anyone has ever experienced similar behavior from a Duo?

I have not experienced your issue. My 280c works fine with external ADB keyboards/mice through both the duo dock and the mini duo dock. Given you mentioned you have been able to power other devices through that port just fine, that would probably rule out 2 of the 4 pins (VCC/GND) and for your issue, you don't have to worry about the power switch pin either. So you only have to worry about 1 pin, the data one, and as @Arbee suggested, you should beep it out from the dock connector back through the logic board. May want to eyeball the dock connector as well to see if there's anything that looks weird.