Non-working floppy drive

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courseddent
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Non-working floppy drive

Post by courseddent » Sat Aug 01, 2020 7:05 pm

I recently bought a "working" Cumana CS100 floppy drive off ebay, and just got round to trying it and it doesn't work:

https://www.youtube.com/watch?v=lG6KAHNIPYI

The stepper motor seems to be struggling to move the head, although the head can be freely moved manually. Any ideas how to fix this? First thing that sprung to mind was a recapping, but couldn't see any significant large ones on the board.

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danielj
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Re: Non-working floppy drive

Post by danielj » Sat Aug 01, 2020 7:47 pm

Don't buy into the "all faults are bad capacitors" story as perpetuated by various retro-communities! (there are good reasons to replace in certain circumstances but those revolve around non-working PSUs, having an Amiga 600 or 1200, or a ZX Spectrum 48k).

Check the wires and connection to the stepper? Looks like poor contacts. Can you take a picture of the PCB properly? Cumana used many different makes of drive in their boxes.

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Wheel_nut
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Re: Non-working floppy drive

Post by Wheel_nut » Sat Aug 01, 2020 8:42 pm

courseddent wrote:
Sat Aug 01, 2020 7:05 pm
I recently bought a "working" Cumana CS100 floppy drive off ebay, and just got round to trying it and it doesn't work:

https://www.youtube.com/watch?v=lG6KAHNIPYI

The stepper motor seems to be struggling to move the head, although the head can be freely moved manually. Any ideas how to fix this? First thing that sprung to mind was a recapping, but couldn't see any significant large ones on the board.
Is that a video of your drive? What make is the bare drive in the enclosure? Cumana used many different bare drives in their enclosures so pictures of the maler's label and the top side view would help.
#1 BBC Model B Issue 7 + 1770 DFS + Dual TEAC Floppy
#2 BBC Model B Issue 7 + 8271 DFS + Dual Floppy + Speech
#3 BBC Model B Issue 7 + 8271 DFS + Cumana Single Floppy + PiTubeDirect on KenLowe's Tube Level Shifter

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vanekp
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Re: Non-working floppy drive

Post by vanekp » Sat Aug 01, 2020 10:32 pm

do you have any jumpers set on your keyboard for drive stepping speed maybe its trying to step too fast.
Peter.

courseddent
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Re: Non-working floppy drive

Post by courseddent » Tue Aug 04, 2020 4:17 pm

vanekp wrote:
Sat Aug 01, 2020 10:32 pm
do you have any jumpers set on your keyboard for drive stepping speed maybe its trying to step too fast.
Didn't think of that - good suggestion. I went and tried various different timings, but unfortunately the problem remained.

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Re: Non-working floppy drive

Post by courseddent » Tue Aug 04, 2020 5:08 pm

Wheel_nut wrote:
Sat Aug 01, 2020 8:42 pm
Is that a video of your drive? What make is the bare drive in the enclosure? Cumana used many different bare drives in their enclosures so pictures of the maler's label and the top side view would help.
Yes - the video is the actual drive. I've attached some more detailed pics of it, looks like a Mitsumi D501?
IMG_20200804_161425648.jpg
IMG_20200804_161602727.jpg
IMG_20200804_161036739.jpg
IMG_20200804_161046678.jpg

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Re: Non-working floppy drive

Post by courseddent » Tue Aug 04, 2020 5:26 pm

danielj wrote:
Sat Aug 01, 2020 7:47 pm
Don't buy into the "all faults are bad capacitors" story as perpetuated by various retro-communities! (there are good reasons to replace in certain circumstances but those revolve around non-working PSUs, having an Amiga 600 or 1200, or a ZX Spectrum 48k).

Check the wires and connection to the stepper? Looks like poor contacts. Can you take a picture of the PCB properly? Cumana used many different makes of drive in their boxes.
Hehe, yes - it's very easy to jump to the capacitors causing all the ills of the world conclusion! I had a look at the stepper cable, and reseated the connector - all looked in reasonable shape, although can't test continuity of the cables as they disappear into the stepper.

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vanekp
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Re: Non-working floppy drive

Post by vanekp » Tue Aug 04, 2020 10:04 pm

Does the head carriage move up and down freely (taking into consideration the resistance the stepper motor put on it)?
a lot of carriages get very stiff as the lubrication drys up and they get a build up of dirt on them.
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Re: Non-working floppy drive

Post by Coeus » Tue Aug 04, 2020 10:22 pm

courseddent wrote:
Tue Aug 04, 2020 5:26 pm
danielj wrote:
Sat Aug 01, 2020 7:47 pm
Don't buy into the "all faults are bad capacitors" story as perpetuated by various retro-communities! (there are good reasons to replace in certain circumstances but those revolve around non-working PSUs, having an Amiga 600 or 1200, or a ZX Spectrum 48k)....
Hehe, yes - it's very easy to jump to the capacitors causing all the ills of the world conclusion! ...
Personally, I don't like doing needless work or paying to replace components that are working so I am reluctant to indulge in the "replace bits until it works" approach whether it is capacitors or anything else. When swapping parts around is easy, and you already have spares, then fine but even then having some kind of method is good.

Otherwise trying to think logically, runs tests where you can, and asking for help on here seem like much better approaches.

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retroclinic
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Re: Non-working floppy drive

Post by retroclinic » Wed Aug 05, 2020 3:46 pm

What FDC do you have? If it's a 1772, then no speed setting will be slow enough for that drive.

Thanks, Mark.
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retroclinic
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Re: Non-working floppy drive

Post by retroclinic » Wed Aug 05, 2020 3:50 pm

..as for cap replacement, on a motherboard generally I agree, if it ain't broke, don't try and fix it, but for Power supplies, especailly the Model B ones, it's a MUST. This PSU and it's caps looked perfect from the top, it was only on dismantling....
IMG_4645.jpg
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courseddent
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Re: Non-working floppy drive

Post by courseddent » Wed Aug 05, 2020 7:00 pm

After discussing this with Retroclinic, it sounds like this drive is too slow to work with the 1772 chip in my BBC Master, so may actually be working fine, just not compatible.

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Re: Non-working floppy drive

Post by Kazzie » Thu Aug 06, 2020 6:30 am

courseddent wrote:
Wed Aug 05, 2020 7:00 pm
After discussing this with Retroclinic, it sounds like this drive is too slow to work with the 1772 chip in my BBC Master, so may actually be working fine, just not compatible.
That's quite possible (I have some ancient full height single-sided Olivetti FD501s that are too slow for a 177x), but I wouldn't have expected a drive with such a small circuit board, and all the control circuitry integrated into a single IC, to be that "old and slow" .

Sadly, I can't find any further details on the D501 online. Are there any markings that could be a datecode (on the PCB chips, or labels) that could give an idea of when this was built?
BBC Model B 32K issue 7, Sidewise ROM board with 16K RAM
Archimedes 420/1 upgraded to 4MB RAM, ZIDEFS with 512MB CF card
RiscPC 600 under repair
Acorn System 1 home-made replica

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