ZX Interface 1 with Microdrive problems

[bwinkel67]

Does anyone know best way to debug a microdrive. I seem to have a faulty one. When hooked to my Spectrum via ZX Interface 1, it formats a microdrive cartridge anywhere from 2K to about 35K. I can even save and load a program. It's never consistent and mostly settles on between 15 and 20K. The same microdrive cartridge on the QL formats to about 216 sectors (108K).

When the microdrive is hooked to the QL it cannot read any cartridges and fails to format any -- presumably because on the QL the cartridge has to format to a minimum number of sectors. So the microdrive sort of works but something is faulty. I changed out the motor with a spare and that didn't change anything.

What would cause it to partially work but miss so many good sectors when formatting? Would a bad ULA cause that? Or is it something else? (bad capacitors, faulty voltage regulator, etcc...)

[1024MAK]

I don’t know. But has the head been cleaned? Does it look worn?

If the ULA was faulty, I would not expect it to work at all.

Mark

[bwinkel67]

I don’t know. But has the head been cleaned? Does it look worn?

If the ULA was faulty, I would not expect it to work at all.

Mark

I don't think the head is worn and I have cleaned it thoroughly with isopropyl alcohol and a cotton swab. The center part still looks shiny and you can still see the distinct wingdings. Comparing it to the QL heads, it seems the same. Anything else that would be signs of a worn head?

I think the next step is to check for voltages and make sure the capacitors, resistors, and other passive parts look ok. I believe the ZX Interface 1 works properly as the seller tested it (and sent video) of it working...they were reputable.

I did find out on the QL forum that due to speed differences in how the drive is controlled, it likely would not be able to format a cartridge hooked to the the QL...but should be able to read/write one...so I will investigate that further. Didn't realize there was such a difference.

[Paul]

On the motor sits a rubber roller. This can need cleaning and if heavily used in the past it's a good idea to remount it upside down so the tape is moved by the "fresh" part of the rubber.

[bwinkel67]

On the motor sits a rubber roller. This can need cleaning and if heavily used in the past it's a good idea to remount it upside down so the tape is moved by the "fresh" part of the rubber.

Thank you. I have used two different rubber rollers and cleaned and rotated each. There doesn't seem to be any wear on them and the rubber seems soft (i.e. not plastic-like).

[bwinkel67]

Ok, I'm finally at 83K formatted, which is likely the best I can expect. I followed the Byte Delight refurbishment guide.

https://www.bytedelight.com/?page_id=1623

So, I changed the two capacitors (0.22uf and 0.47uf) with new ones (two 1uf's). I need to locate a couple of 100pf ceramic capacitors to add to the board to finish the refurb. I also changed out the motor and changing it back did not work (i.e. it gave me 0k or 1K most of the time) so the motor, even with lots of oil, was at issue.

[bwinkel67]

I'm up to 87K now. I had a second spare motor and that did even better. I'll need to check if it will now read/write files on a QL formatted cartridges when hooked to a QL. Before the second motor swap, it could get the directory listening hooked to a QL, but nothing else.

I found the following feature weird...when you poke 23791,N where N is the number of copies, when you use the SAVE command, it saves that many copies. I did a couple of files with N being 75 and it worked (quick way to fill up a drive). Supposedly, you now have to delete each file 75 times to get rid of it. Not sure what it does if one of them gets corrupted...does it go to the next one? It doesn't show you the number of copies you have, it just appears as a single copy that won'd disappear when you use the ERASE command. Just a very odd feature.