Service and cleaning of Micropolis floppy mechanisms from an 8050

[crock]

Hello gents,

I recently acquired a 'pile' of 6 Commodore IEEE drives which were stored in a barn since the late eighties. There are three 4040's and three 8050's.

All of the drives were full of dust, grease and insect remains and the cases are badly rust pitted. Nevertheless, the Shugart mechanisms in 4040's were easy to strip down and clean. As long as I didn't loosen the clamps on the stepper motor, there was no risk of affecting the alignment. Therefore I managed to get two fully working 4040's from the three. I also cleaned up and resprayed the cases so they also look in great condition now.

I would like to achieve the same with the 8050's but the Micropolis 1006-2 mechanisms seem far more complex and there seems to be relatively little that I can strip down without affecting its setup. This isn't helped by a lack of literature on the net so I'm looking for anyone who has any tips on stripping down and cleaning of these drives and maybe any procedures for setting them up correctly afterwards. I don't include the alignment in this. I would leave the stepper motor in place.

Regards,

Rob

[Chuck(G)]

The 1006 is close enough to the 1015 and 1016 drives that the 1016 maintenance manual should be a good guide, at least in matters mechanical:

http://bitsavers.informatik.uni-stut...nual_Dec79.pdf

I believe that CBM put their own electronics board on the 1006 drives, so the electronics aspect of the manual probably doesn't mean much. In my own experience, the big problems with the Micropolis drives were the hub-clamp assembly and keeping the leadscrew clean and lubed.

[crock]

Perfect! Thanks Chuck. I'm not too worried about the electronics, it's the mechanisms i'm struggling with.

cheers, Rob

[KevinO]

Thanks here too. While I'm currently working on resurrecting C64's, I will eventually get back to my PETs, and I have 2 (or was it 3) non-working 8050s, so that might be very useful.

Oh and a question for Rob...I have a "working" 4040 that seems to erase disks if I turn it off while there's a disk in the drive. I have a vague memory of documentation that says not to turn the drive on or off with a disk inserted, but this one seems to do it consistently. Do your 4040s exhibit that behavior?

[dave_m]

I have a "working" 4040 that seems to erase disks if I turn it off while there's a disk in the drive. I have a vague memory of documentation that says not to turn the drive on or off with a disk inserted, but this one seems to do it consistently. Do your 4040s exhibit that behavior?

Power cycling with a diskette in the drive will usually corrupt the diskette especially if there is an unbacked-up file on the floppy.

One usually got into the habit of removing floppies after the SAVE or LOAD.

[MikeS]

I've got a few of those Micropolis 100-track drives, both the bare mechanisms in the 8050s as well as the complete versions used in some CP/M systems; FWIW, the problems I've seen (aside from the standard clean/lube rails & drive screw) are unstable motor speed, loose or worn head pressure pads, and a defective microswitch.

[Chuck(G)]

The early Micropolis drives did not turn on the motor when the disk was inserted, leading to a lovely "wrinkled" hub area. Micropolis later added a microswitch to turn on the motor when the drive door was being closed. As far as I can tell, the big difference between the 1015 and the 1016 is the way the siwtch is activated.

[crock]

Oh and a question for Rob...I have a "working" 4040 that seems to erase disks if I turn it off while there's a disk in the drive. I have a vague memory of documentation that says not to turn the drive on or off with a disk inserted, but this one seems to do it consistently. Do your 4040's exhibit that behavior?

Not that I have noticed but then again I am usually pretty good at remembering to pop the disk before power cycling. As you say, the documentation is pretty clear on not doing it but I also recall the circuitry isolates the head on power up and power down to avoid it. When I was a kid using a 1541, I consistently ignored this advice without any ill effects that I remember.

FWIW, the problems I've seen are unstable motor speed, loose or worn head pressure pads, and a defective microswitch.

That's useful to know, thanks Mike. WRT to the head pressure pads, has anyone successfully fashioned a replacement? A couple of the ones in the 4040's are worn and make a a slight squeak as the disk rotates. I would have thought the pad could be replaced using some suitable material.

The early Micropolis drives did not turn on the motor when the disk was inserted, leading to a lovely "wrinkled" hub area. Micropolis later added a microswitch to turn on the motor when the drive door was being closed. As far as I can tell, the big difference between the 1015 and the 1016 is the way the switch is activated.

These 1006-2's have a micro-switch that briefly rotates the disk as the disk is clamped.

I have realized that I can get at most of the mechanism to clean it by removing the clamp support plate. I can then get in there with cotton buds and a damp cloth to remove the worst of the crud. The document you linked to then explained how to align the clamp assembly, so thanks again Chuck.

Rob

[Chuck(G)]

I'll add that Micropolis' shipped-from-the-factory drives were horrible as regards azimuth. We began screening drives for head azimuth and started returning about one-third of what we were shipped. Eventually, Micropolis got their act together, but that's one aspect that's often overlooked in these drives.

[crock]

So I've managed to get 5 fully working mechanisms from the 3 8050's which is OK as my aim is to try and get 2 fully functional units. None of the digital boards worked initially but I am not to worried about that. The first had a dead 6502 which was easily replaced, the second has a dead 3446 transceiver which was sourced from evilBay and the third has a power issue which means the fuse blows even though the board is functional. Odd.

Where I am hoping to get some help is with the analogue boards. Only one is working, the other 2 just give me read errors, the motor motor controls *appear* to work but I do not know that for sure, so I think it's the amplifier circuitry. There is 4 test points on the board but I have no documentation to help me to know what to look for. If anyone has any tips for troubleshooting the analogue boards for Micropolis drives in a Commodore 8050 it would be great!

Regards, Rob