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CoCo FD-502 Floppy Problems

C

carangil

Experienced Member
Joined
Jun 3, 2009
Messages
285
Location
Oakland, CA
I got my CoCo2 out of garage storage and back on my desk. The FD-502 can't read anything! I can't even DSKINI any disks. If I remove the cover, when I DSKINI I see the head count out about 15 times, then it seems to hit the mechanical stop, and then jams against the stop for the rest of the tracks. I'm looking for anything obviously wrong mechanically. Are there any known issues with this?

I am also wondering if the ribbon cable between the cartridge and the controller has gone bad. Tell me, do these disk drives have different stepping mode sizes? Could the drive be taking double-size steps because some wire isn't grounded or something? ( I'm thinking of PC drives where a DD disk in a HD drive is handled be stepping twice.)
 
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Ok, so I found thr problem. This 'C' shape was in the way. I didn't notice it until I tool the disk out and started loolong at how it steps in and out. It works now, but now I have an extra piece. Where does it go? I end way too many of my projects with a piece left over.
 
Dunno...

Double Stepping, as far as I know, is a peculiarity of certain drives, especially on PCs, and I'm not sure it's normal. If the CoCo system has any options for 40 or 80 Track disks, then it's possible, otherwise it's unlikely. Normally, a 40T drive would try to step 40 times. And it doesn't sound like your drive is double stepping, which would be 40 tr on an 80 tr drive.

Please bear in mind that operations of a FDD may be dependent on sensors, involving light. Operating the drive in full light MAY interfere with this. By all means check what's happening this way, but provide some shading/shadow so that light is limited but you can still see what's happening. Some stepper motor operation is also dependent on such a sensor to set Track 0.

If operation is similar BOTH for a known blank disk and a disk that SHOULD have something on, then two possibilities come to mind. There may be other problems as well. However, the head may not be reading, make sure they're cleaned. The disks may be damaged, and the disks that should have something on no longer do. I assume that DSKINI is a sort of format routine, so maybe you're NOT trying to read an existing disk?

Geoff
 
It goes on top of the head, you can see the left-over of the adhesive where it once was. It can probably be left out. Test it for a while without the C-shape and if the drive runs fine just leave it out.
 
Your second message posted while I was replying.

The 'C' piece looks like something connected with the head, maybe to protect bits of wiring. Maybe dislodged if disk inserted roughly? Maybe can be clipped back? I'd suggest the 'C' surrounds the actual head, but still allows the head to contact the surface of the disk.

Geoff
 
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