I popped open the QX-10 again today and swapped the A and B drives. When I had them out, I observed that the B drive (the then Right drive, second picture) has a chip that the A drive (the then Left drive, first picture) lacked.
“Hmm,” I thought, “maybe that’s why the A drive wasn’t working. Maybe somewhere along the line it lost a chip it needs, maybe I’ll need to find a replacement chip.” I reversed the drives (and the DIP switch settings, which was probably the most important thing), reassembled, et voilà:
Cool. Except the (now) Right drive (still labeled “A” but now logically “B”) wasn’t working at all. Well, except that its activity light was coming on at a very, very low level and just staying lightly lit.
I was distracted from thinking about that further by the thought that I should right now back up the boot disk onto the new floppy media I had (though this was not going to be possible regardless, all of the copy functionality I had available on the boot disk requires both drives to be working). But, once I popped out the boot disk, I couldn’t convince the left drive to accept any further disks, even the one I had just popped out. The problem, I correctly guessed, is that spring return mechanism mentioned in the previous post about the drives wasn’t returning. The pad didn’t want to slide back, it needs to be lubricated. If it doesn’t slide back, then it remains in a kind of unready state where the physical disk capture mechanisms won’t go.
So, I took it all back out and decided that at least until I get that lubricated, I need the drives out in the open so that I can pop the pad back with my finger. So, now the QX-10 has its drives sitting on top, though it all still works as well as it did with them inside.
Until just a little while ago, I was thinking that what was wrong with the (now) Right drive is that it was missing that chip. This is the chip:
However, when I looked it up, the Peacon Vintage Blog wiki told me that it is: “a 150-ohm resistor network in a 14-pin package. It can be used to terminate the floppy disk drive bus.”
So, this is why only the (then) Right drive and not the (then) Left drive had one, and also might be the very reason why the (now) Right drive isn’t doing anything. The chip is a terminator. It’s telling the drive bus that the Left drive is the end of the line, and there shouldn’t be any more drives expected (even though the [now] Right drive is connected after it). So, now I still don’t know if the (now) Right drive works or not, since I disabled it by accident.
Not sure what I’ll do next. I might try to transfer the terminator chip to the (now) Right drive, or I might swap them back and see if I can do anything to get the (now) Right drive to work, since I have now seen that the rest of the machine basically works.