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Microdrive nightmares

falter

falter

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Jan 22, 2011
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Location
Vancouver, BC
I have two QLs - one I bought with a ton of wafer carts and the other I got cheap with non working keyboard and no power supply. Both are US models.

The second unit came with a PSU. I replaced the keyboard membrane as it needed it also and began experimenting with the microdrives. The original mdv1 in the newly repaired machine would not read anything. Probing the ULA with scope showed it was not really reading or writing anything.

I then swapped one of the microdrives from the non working machine, and now it was actually trying to read the wafer carts, although without success. On one or two I managed to get a directory listing but the felt pads disintegrated.

I have probably three dozen wafer tapes, and literally almost all of them are missing the felt pads. Like maybe 4 still had them, kind of. I went looking for replacements and settled on this, which is a bit too thick but I figured could be cut down. After an hour of frustrating cutting and trimming, I managed to get the microdrive to at least try to read. I even got the Word Processing cart to bring up it's boot screen. But the tapes just ran forever without conclusion, and on reattempts they would not boot at all again.

I've noticed that trimming or pressing the pad down or adjusting thickness with new pads seems to bring different results. Im wondering if that's the entirety of my problem.

Also, several cart tapes snapped. Is that a common thing in aged wafers or should I be worried about the drive, I wonder. If they are like other tape media I'm thinking if they sat for years the tape on the spool may have fused together and simply snaps when first run again.

Just wondering if anyone has a source for accurate felt pad replacements, as messing around with those seems to be the only thing that delivers a bit of progress.
 
I don't think there's any consensus on what pads are best - same issue with floppy drives. I try to avoid plastic based felts, and go for what I think are high temperature felts, so I cut up those hard felt disks they have with Dremels and rotary tools ( the things that usually stay left over when you've consumed all the useful parts of a mini tool accessory pack ) and I cut them with a razor knife into slices, and the slices into felt pads... I use CA glue, but I get the feeling I could make a better choice of glue.

There are discussions of different felts with respect to single sided floppy drives you can consider - I think a few people sell felt, but without knowing what is good and bad, I assume many just cut strips of sticky back felt into small squares and mark up the price - I don't know if that's good or bad - I have some here to test, but never got around to any longevity tests.

For microdrive cartridges, the felt is ALWAYS worn, and the broken bits can end up inside the cartridge and cause it to seize eventually, so never be tempted to try an old one ever. Also, the metal pads get pretty worn over time, and if they go, the cartridge is cactus.

Additionally, depending on storage, some cartridges look OK, but their coercivity has gone up so much they need to be degaussed to work well since they don't write or erase all that well, and drives are all temperamental, with each drive having a personality.

Most of the drives I get are good, and work with a little cleaning. Some were dead. QL ones seem to fail more than others.

You can get a microdrive emulator pretty cost effectively that emulates 127K drives, and there's a few. more than once I've thought of buying one. I even assisted in the development of one, and created a genuine 640K microdrive format that actually worked when tested on an unmodified spectrum, which I thought was pretty cool... So I filled it with images from ZXART and a small basic program to sequentially load them with a pause between. It was neat because it worked with an unmodified Spectrum and Interface 1, and used repeated sectors in such a way that you could fill it with lots of files... Up to 127 files, and 640K total size.

Check though whether a drive emulator is Spectrum or QL - The Spectrum data rate is around 80 Kbps ( x2 for two channels ) but the QL is around 100 Kbps (x2) and they start on the opposite head/channel to the ZX Spectrum.

There are some good signal information on the ZX Wiki in the UK that I uploaded that explain the formats in more detail.

Regards
David.
 
cj7hawk said:
To extend your experiment with the Ebay felt, I went with this one;

Let's swap experience details after we fix some cartridges :)
Click to expand...

OK, my felt is too thick, but the sticky back on it is the real deal - and once stuck doesn't come undone, yet the paper comes off easy enough.

I'm finding that once I cut it down, I can trim the thickness OK with a razor knife.

I got some good results and some very poor results - depends on the cartridge - but I think I have cable issues so am making up a new cable, but can't find my roll of 1/10" ribbon cable... Thought I had a roll, but that's 2mm.

Then I'll test again.
 
I cut up little pieces myself for archiving QL carts. It's worked well for years and hundreds (probably thousands by now) of carts. I also sell the pads, but don't make a big thing out of it as it's time consuming to cut them up! ;)

Tips on QL data recovery

Data recovery after re-felting and using mdump from Daniele Terdina.
qxl.win
 
I've tried a couple different felt pads now and have had almost no luck. Once I got the drive to bring up the title screen for the word processor.. but that was it. Several carts have snapped their tapes. The machine works well otherwise. Need to figure this out.
 
Snapped tape is quite unusual. Perhaps they were stored badly and are too far gone to properly recover (damp, mould, heat cycles... other environmental damage).
 
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