Using ZX Microdrives on the QL

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Re: Using ZX Microdrives on the QL

Postby Timbucus » Fri Apr 21, 2017 1:49 pm


Sorry the ULA replacement comment was intended for my fourth 'faulty drive' that I cannot get to even recognise a cartridge - it just stops with microdrive not found (without restoring the ratchet or a new roller and plastic wheel of course it will never work as it has the dud roller swapped to it) - if you try and use it to format (with a roller restored) it stays white on the third stage which the service manual (para 3.2) says indicates "noise on the write line" from either motor alignment, ULA or regulator (The reg is producing 5.07v without ripple but maybe that is a bit high so perhaps I could swap that first - I had a spare ULA that seemed the best approach as I don't have a motor alignment jig - I am asking anyone I can find with engineering tools to make me one... It can also go into a hard lock of the tape spinning which is why I suspect maybe a ULA rather than the motor/regulator - if the amps are flawed then the signal will be noisy? I'm clutching at straws really as they are getting so rare and expensive it seems a share to write on off! I have not swapped electrolytics or polyester caps on this to act as a bit of control to work out what the actual fault is...

This is sort of the same but, worse than the symptoms I am getting on 04-083529 but, that does seem to get some sectors written although I have seen the format very low between 1 and 50 sectors only again it seems to be more white on the third stage of the format. It is this one that I have swapped the two electrolytics and the polyesters which gave a much cleaner signal on the scope during the read of a formatted cartridge and got it at least going to read data written on other cartridges. (The reg on that reads 4.99v no ripple). Again this supports the noise on the write line theory. I.e. it can read but, written data is unreliable.

I did the resister swap for the QL test as it does read cartridges so I could at least see if that was helped but, it didn't - of course format would never work as it doesn't on the Spectrum!

I tried to look for my walkman to check the head but, it occurred to me that it was play only so there would be no erase head - and all my old tape units have a separate erase head.


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Re: Using ZX Microdrives on the QL

Postby Dave » Fri Apr 21, 2017 8:34 pm

First check the caps, and make sure no diodes have been damaged by failed caps. Check the wiring and solder connections. 5.07V is well within tolerance. RWAP has a bunch of the ULAs and they're economical. Buy two, support his business!

You don't need a jig to mount the motor. It uses countersunk screws that really leave very little movement for positioning the motor. I have just 90% tightened the screw that would be covered by a microdrive, started the other screw, inserted a possibly sacrificial mdv cart, then formatted it and tightened down the other screw with it running. 100% success rate.

I have a roller that I cut a notch in and glued a tiny magnet into, so I can use a guitar tuner to set the motor speed to ~2260 rpm (1/3rd of the way between C#7 and D7). Both C# and D work, but closer to C# usually yields an extra two or three sectors.

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Re: Using ZX Microdrives on the QL

Postby tcat » Sat Apr 22, 2017 4:43 pm

Hi Timbuctus,

I am only a hobbyist, my tools do not match advanced skills of people here. I set myself on a QL and MD learning quest a while ago. MD unit is so simple device one may wonder why it is ill-reputed at all. I tinker with ZX as well, I have a single MD drive though.

I also got involved in QL preservation projects, as a result a little tool came underway that can indicate a drive speed with 1/4 secs accuracy (RPM is recalculated from a loop pass time) using known good formatted cart may have data on it, is non destructive as it goes in reading loop only.

I mostly learn from people here often also from their software.
You may also follow the threads here, one re MD units I stolen (my apologies Derek).

I sent you PM with my email.


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