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

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

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: 

 

https://youtu.be/0CfAzbqSXl8

 

Thanks for any tips or suggestions! 

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I can't help much on

I can't help much on troubleshooting. But I can clarify a couple things.

 

 

On a IIe, the drive will spin constantly on boot if it doesn't think a disk is in the drive. So it seems that your drive isn't reading the disk at all. Otherwise it would attempt a boot vs continuously spinning.

 

 

As for the belt, Console5 only sells a Disk II belt for Shugart drives. And it's slightly different than the Alps drive belt. Your drive looks like an Alps drive (only the early Disk II were Shugart). So if you bought the DIsk II belt from there, it's the wrong one.

 

 

But he does sell an Alps belt for Commodore 1541 drives. As the Alps chassis is the same between the 1541 and the later Disk II, that belt should work if you really need one. I've mentioned that to him in the past, but for some reason he never made the reference on the store for Alps Disk II. 

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Calibrated the speed?

If you just changed the caps and didn't break anything :-), then it's probably just the drive speed which needs adjustment. That's especially the case if you changed the caps on the motor controller PCB.

There is a trimmer to adjust the speed. You need an old incandescent light bulb, flickering with your 60 Hz (or 50 Hz) mains frequency - not a modern LED light etc. Put it next to the drive and adjust the spindle trimmer until it appears the "stroboscope" stripes on the disk pulley no longer move forward or backward when the drive spins (the stripes for 60 or 50, depending on your mains frequency, of course). Once the speed is about right, the Apple should recognize the disk.

Once you're able to boot, you need to fine tuning. There is a diagnostic disk (I forgot which), which shows whether the drive is spinning too fast or too slow (when using a known good disk). To my experience, reading is slightly more tolerant than writing. So when you managed to get the drive to boot again with the simple "stroboscope" adjustment, it's often not good enough yet for writing.

And as Nick said, it's normal that the drive keeps spinning when it's not recognizing the disk. The machine has no way to tell whether a disk is present or not, until the speed is right and the controller picks up a valid signature on track 0. This is all part of Woz's optimizations to remove all unnecessary sensors from the drive.

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Awesome info MacFly! Much

Awesome info MacFly! Much like calibrating the old vinyl turntables. This procedure reminds me of tuning Technics 1200s with the built in strobe on the power knob and the dots on the spinning platter. 

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Locksmith

The copy program Locksmith (for example v.5) has a menu option "disk speed" which can be used to calibrate the disk speed.

It just requires a blank disk to write on.

The standard speed is 300 rpm.

 

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Did the other suggestions help?

Did you get this figured out with the other suggestions? If not, I'd be cuirous about what you did for finding replacement caps and how you went about selecting those you did. Caps today are different and the differences sometimes are not obvious even to an EE unless they dig deep into the datasheets. 

For what it's worth, I just recapped a SC20HD, //e,  and IIGS. Even though I got the GS PS and MB kits from console5 I did not use them. I wasn't happy with some of the caps (for example I didn't like the GS caps for the sound being the same as ones for power filtering and not audio grade caps. I don't really know if there's a big difference, but the originals are different so that's important to me). It's a lot more work and some trial and error, but I went to school for this so I might as well use my knowledge and I'm happy with my results. That said, there's more to a cap than its capacitance rating...

One suggestion I had for you on your belt... I'm assuming the original when removed is still "circular" and not deformed because can cause issues. There are also belt conditoners which may help with the rubber elasticity, flexibility, and grip. I'm pretty sure consonle5 has several belt kits designed for the different drive internals, make sure you got the correct one for your spindle mechanism. I would also be very careful with "spray" lubricants, you don't want those vapors getting on sensitive surfaces (i.e. drive head)

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Spaceboy,yYou never mentioned

Spaceboy,

yYou never mentioned what this drive did before you recapped the analog board.  If this drive was working  and now it’s not reading, make sure you don’t have one of the 4 ICs in backwards or in the wrong location. I had a drive that stopped reading after I was playing with the ICs and I found out I had one in backwards. The one that controls the read circuit no doubt. And the LS125 is notorious for being blown. Plug that ribbon cable in one row off and it’s goodbye. Trust me I’ve done it several times myself.  And the drive will do exactly like yours, stop reading. So my advice, make sure your ICs are on correctly and try swapping out the LS125. 

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A blown 74LS125 will often

A blown 74LS125 will often cause a drive to corrupt disks too...

 

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