Microdrive failure after felt pad detaches - ideas?

Nagging hardware related question? Post here!
BleatingSheep
ROM Dongle
Posts: 4
Joined: Sat Jan 25, 2020 6:49 pm

Microdrive failure after felt pad detaches - ideas?

Postby BleatingSheep » Sun Jan 26, 2020 11:27 am

Hello all,

I've been reading the forum for a long time but haven't needed to post until now. Yesterday I was copying some old programmes from microdrive cartridges I had found in a box to disk. All was going well with both microdrives on my QL working normally (as they have done since I got it in 1984/5). Unfortunately as a cartridge was being read in mdv1 it made an unpleasant noise and stopped reading. When I pulled it out I saw the felt pad had disintegrated.

On putting a different (known to be working) cartridge into mdv1 I got a "Not found" message. It read correctly in mdv2. I powered down and tried again. The second time I tried I still get a "Not found" in mdv1 for all cartridges and mdv2 now continuously spins the tape but never returns any data.

I've taken the QL apart and both motors are turning, the pinch wheels and tape heads seem clean and the pinch wheels haven't worked up their spindles. When I turn the QL on and press F1, mdv1 spins up and down as normal. However, it decides very quickly - a matter of a second or two - that it has "Not found" anything when I do "dir mdv1_". "dir mdv2_" just spins forever.

Does anyone have any ideas?

Many thanks

Mark

P.S. The QL itself is still working correctly with my Trump Card and floppy drive.


User avatar
Chr$
Super Gold Card
Posts: 545
Joined: Mon May 27, 2019 10:03 am
Location: Sachsen, Germany

Re: Microdrive failure after felt pad detaches - ideas?

Postby Chr$ » Sun Jan 26, 2020 11:38 am

Check what you have access to from the top, especially that the 7805 is outputting near enough exactly 5v. And that the 2 electrolytic capacitors are ok.

What happens if you try to format a cart? Personally with original felt pads I wouldn't trust any of them. I'd say, once you have some known good re-felted carts to continue fault finding, hopefully it's just the felt. (I'll send you a decent cart for the cost of postage if you like).


Collector of original and some newer QL related computers, accessories and software even though I don't understand how any of them work.
Original BBQL's: 3x German, 1x UK model (plus quite a bit of other old stuff)
Custom AT cased QL system with Gold Card, Qimi mouse, Hermes and MFM HDD
PC with QXLII card installed
Q68 also present

Ask me about near NOS re-felted good quality Microdrive Carts - many available.
BleatingSheep
ROM Dongle
Posts: 4
Joined: Sat Jan 25, 2020 6:49 pm

Re: Microdrive failure after felt pad detaches - ideas?

Postby BleatingSheep » Sun Jan 26, 2020 11:46 am

Hello Chr$,

When I try to format a cartridge I know to be good (one that I formatted from a different batch earlier in the day), unfortunately I get the same behaviour. I'll test the 7805 and the electrolytic capacitors this afternoon. I do wonder if, when the cartridge lost its pad and seemed to jam, that I've blown a capacitor. I'd be surprised if it was the microdrive ULA because I don't think it would spin up at all.

Thanks,

Mark


User avatar
tofro
Font of All Knowledge
Posts: 2014
Joined: Sun Feb 13, 2011 10:53 pm
Location: SW Germany

Re: Microdrive failure after felt pad detaches - ideas?

Postby tofro » Sun Jan 26, 2020 11:59 am

When the microdrive spins up and instantly comes back with "Not found", then stops, this is a relatively sure sign it doesn't see a gap, thus assumes the tape isn't spinning or there's no cardridge in the drive at all.

If you have really safely verified the tape actually spins, it is likely that
  • the gap detection circuitry in the drive ULA headboard is defect.
  • the read head itself is defector lost its connection to the ULA
No other parts than these two are actually involved here.

I see no good reason apart from pure coincidence that this should be caused by the incident with the vanished felt.

If you are into electronics, exchange the complete drive, or exchange the headboard ULA (IC 29) or Read head.

Tobias


ʎɐqǝ ɯoɹɟ ǝq oʇ ƃuᴉoƃ ʇou sᴉ pɹɐoqʎǝʞ ʇxǝu ʎɯ 'ɹɐǝp ɥO
BleatingSheep
ROM Dongle
Posts: 4
Joined: Sat Jan 25, 2020 6:49 pm

Re: Microdrive failure after felt pad detaches - ideas?

Postby BleatingSheep » Sun Jan 26, 2020 8:03 pm

Hi Tobias,

Thanks. I'll follow your advice and explore the ULA and r/w head. I agree with you that it's odd that it happened as the cartridge broke. I wonder if too much current briefly flowed through the ULA. I'm comfortable with electronics - I spent the afternoon reading the QL Service Manual. I'll let you know how I get on.

Many thanks to everyone,

Mark


Martin_Head
Super Gold Card
Posts: 530
Joined: Tue Dec 17, 2013 1:17 pm

Re: Microdrive failure after felt pad detaches - ideas?

Postby Martin_Head » Mon Jan 27, 2020 10:45 am

I know you say that the tape head looks clean. But try cleaning it with a tape head cleaner, or isopropyl alcohol. It may be that some dirt you cannot see is stuck to the head.


BleatingSheep
ROM Dongle
Posts: 4
Joined: Sat Jan 25, 2020 6:49 pm

Re: Microdrive failure after felt pad detaches - ideas?

Postby BleatingSheep » Thu Jan 30, 2020 6:01 pm

Hi,

Last night I carefully took mdv1 apart and cleaned everything - squirty air for the electronics and isopropyl alcohol soaked cotton bud on the tape head.

The squirty air had no effect but full marks to Martin Head for his suggestion about invisible dirt. There was a tiny - and I mean really tiny - piece of black dirt on the tape head and once cleaned everything is working again.

Thanks for all your help,

Mark


User avatar
bwinkel67
Gold Card
Posts: 498
Joined: Thu Oct 03, 2019 2:09 am

Re: Microdrive failure after felt pad detaches - ideas?

Postby bwinkel67 » Thu Jan 30, 2020 7:22 pm

Ah yes, I had that happen on mine as well in the past and a good alcohol swabbing will do the trick. I also add a bit of oil to the motors under the rollers as that can improve reading and writing. I think when I took my QL out of mothballs in the fall neither microdrive would read anything or worse, format anything. Even after cleaning the heads. A few drops of oil and both format and read/write on good mdv cartridges. Still trying to find best re-felting techniques.

But yes, Martin deserves his Gold Card status as hes been very helpful to me on video issues as well :-)



Who is online

Users browsing this forum: No registered users and 7 guests