• Updated 2023-07-12: Hello, Guest! Welcome back, and be sure to check out this follow-up post about our outage a week or so ago.

Recapped my Disk II drive and now it's gone from "kinda sorta working" to "not working"

Huxley

Well-known member
Hi all!

I'm deep into a repair + restoration project on an Apple IIe, and while I'm making great progress, I've run into a problem:

I just recapped the Disk II drive, lubricated all the moving parts, etc. However, now when I power up the Apple IIe with a ‘known good’ boot disk in the drive (I have several boot disks I’m testing with), the disk spins and I get the classic “rattle” of the read/write heads shuddering back and forth, but that’s it - no further movement and no data being read. Even weirder: The disk motor spins continuously when it's powered up, whether or not there's actually a disk inserted. Strange!

On the assumption that I goofed something up with the recap work (I’m new at this!), I went back and double-checked everything I did, and as best I can tell, it looks solid. I ‘reflowed’ the soldering I’d done to ensure good connections, and also double-checked that all the capacitors I installed are oriented correctly.
What are some good next steps towards getting this drive working again?

I made a short video to show what I'm seeing - here's the link:

Thanks for any tips or suggestions!
 

volvo242gt

Well-known member
Possible that the ULN2003, 74LS125, or MC3470P/AP chip has fried itself (or more than one have fried themselves).
 

Huxley

Well-known member
Possible that the ULN2003, 74LS125, or MC3470P/AP chip has fried itself (or more than one have fried themselves).
Yeah, that's a super valid thought. I'm thinking hard to my first post-recap test, and I'm now realizing that I may have missed a super important clue: the first time I tested the drive after recapping, the Apple IIe didn't power on - it was acting dead. I thought I'd just failed to seat the Disk II card or the power cable, so I went around re-seating everything and then started testing again. That's when the Apple IIe powered right up, but the Disk II began this weird behavior. I've just found an old forum post saying that the Apple IIe power supply will essentially go into "dead as a doornail" mode when there's a short or other failure in the Disk II, to protect the system. I'm super careful about always plugging the disk cable in correctly so I don't think I killed it that way, but something is definitely funky here.

Time to source some replacement chips!

:)

Huxley
 

volvo242gt

Well-known member
I bet the 74LS125 blew. It's used as a fuse on the analog board... I did have one disk ][ a few years back that had both the 74LS125 and the MC3470P chips blown. I've had good luck with the 74HC125 chips in place of the regular 74LS125 chips, btw. They work the same. So, if your usual electronics supplier is out of the 74LS125 chips, feel free to grab some 74HC125s instead.
 

bibilit

Well-known member
Hard to say from a video, but it seems the drive is spinning way too fast.
The drive will not boot if speed is not around the 300 rpm mark.
that’s the purpose of the black and white stripes on the underside of the wheel.
 

Skate323k137

Well-known member
Having to calibrate the speed after this kind of service seems sensible, I would certainly start there next.
 
Top