General Microdrive woes

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Chr$
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General Microdrive woes

Post by Chr$ »

How about a pinned post detailing all the things you can do to troubleshoot microdrives? They are probably one of the most common/annoying potential issues with original QL's!

This topic with help mainly from Martyn Hill is very good:

viewtopic.php?f=11&t=3178

I've got a problematic mdv at the moment. On known good cartridges (that work fine in my main QL) it seems to 'like' some carts, nearly, and others it doesn't like at all. On the ones it does like the most it can format, load and save short programs, e.g. the basic loaders or even a complete Zkul screen once. Others it won't even dir! And I haven't been able to get it to load anything as large as the Psion exes, even from the carts it likes most.

I have swapped mdv1/ 2 over (2 is worse) and I've also tried a known good mdv unit in both mdv1 and mdv2 position - and that one works perfectly in every situation. So I suppose that rules out the problem being on the main QL board.

I've gone though replacing most of the old capacitors (some were way out in terms of measured values) and seemed to improve things a little. I've scrubbed the roller, tried various other rollers, cleaned the head of course and even went all-in and swapped the ULA, which made no difference at all - in fact the cap changes seemed to be more beneficial. I've also swapped the 7805 and the cap that was across it's 5v. What kind of cap is DC28? Why does it have a DC prefix instead of just a C? I just wondered about that.

I do have an oscilloscope, but not in the same place as the problematic QL! The problematic drive(s) are the flat type with no key. They have a cut trace and an extra connection added which includes a diode. Actually, I haven't checked that diode yet.

Could it be head alignment as it seems to like some carts more than others? Any other suggestions/ideas?


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Chr$
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Re: General Microdrive woes

Post by Chr$ »

Update: After changing all the old capacitors (except DC28) mdv1_ seems to be behaving quite well now!

On to mdv2_ ....


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Ask me about felt pads - I can cut them to size and they have proved excellent for mdv data recovery.
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Cristian
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Re: General Microdrive woes

Post by Cristian »

Chr$ wrote:Could it be head alignment as it seems to like some carts more than others?
I don't know if it actually is, but it might be. Often I have to apply some pressure and/or try different angles in order to get the cartridge read. The cartridges are loose, so on some drives of mine I have to push or move them to certain positions.
Which capacitors did you replace exactly?


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Chr$
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Re: General Microdrive woes

Post by Chr$ »

Cristian wrote:
Chr$ wrote:Could it be head alignment as it seems to like some carts more than others?
I don't know if it actually is, but it might be. Often I have to apply some pressure and/or try different angles in order to get the cartridge read. The cartridges are loose, so on some drives of mine I have to push or move them to certain positions.
Which capacitors did you replace exactly?
All of them! The one electrolytic (mine only had one) and all the polyester/odd looking ones - those are now ceramics. Probably overkill, but it really seems to help.

Once both all checked out fine for all functions I put it all back together and both were unreliable again. I suppose screwing them down could affect the alignment, well it certainly is likely to affect the exact angle at which the cart pushes against the head.

Edit: obviously it could have also been dry joints that are now fresh. Who knows. So all caps and both 7805's changed and I also freshened up some other solder joints along the way and tested the diodes.


https://QXL.WIN
Collector of QL related computers, accessories and QL games/software.
Ask me about felt pads - I can cut them to size and they have proved excellent for mdv data recovery.
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Cristian
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Re: General Microdrive woes

Post by Cristian »

Chr$ wrote:
Cristian wrote:Which capacitors did you replace exactly?
All of them!
:!: I admire your committment.
Another critical point is the MDV ribbon connectors and weak pins. It is not a bad idea to check the solderings on Mdv's PCB side, and add a rigid pins plug


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Chr$
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Re: General Microdrive woes

Post by Chr$ »

Cristian wrote:
Chr$ wrote:
Cristian wrote:Which capacitors did you replace exactly?
All of them!
:!: I admire your committment.
Another critical point is the MDV ribbon connectors and weak pins. It is not a bad idea to check the solderings on Mdv's PCB side, and add a rigid pins plug
Yes, I soldered rows of headers onto the ribbons that plug into the m/b and also checked the solder joints on the mdv board.

They still don't seem to like all cartridges, but I'll put that down to iffy cartridges. Most are ok. Copying between drives is fine, formatting is fine.


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Ask me about felt pads - I can cut them to size and they have proved excellent for mdv data recovery.
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Chr$
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Re: General Microdrive woes

Post by Chr$ »

Here's a little trouble shooting mdv tip that I've just been using:

To check efficient reading of a cart I set up a little prog to load a screen, then clear the screen then load the same screen again in a loop.

While it's doing that, you can (gently) poke the cartridge, pull it, push it, cross your fingers differently, do voodoo, touch some wood, adjust angle slightly etc etc (better with the QL open) and the actual loading of the screen data and that typical pattern process it generates I find a great way of being able to see how well it's reading.

And do the same thing trying various rollers to see it you can get it just right! I have some 3D printed rollers from a chap and they look good but to be honest I'm finding them a bit hit and miss (not for the first time). Just now a cleaned and turned-the-other-way original roller seemed much better, at least for reading a screen.


https://QXL.WIN
Collector of QL related computers, accessories and QL games/software.
Ask me about felt pads - I can cut them to size and they have proved excellent for mdv data recovery.
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polka
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Re: General Microdrive woes

Post by polka »

It's a long time since I used the microdrives, at some time I copied everything I owned to 720k floppies and recently, I transferred again everything to two CF cards for my TDI. But out of curiosity, I tried today my microdrives (on my first QL a JM bought in 1984), they seem to work ok (I only did some DIR commands and three COPY off my original ComputerOne FORTH cartridge - the one with three bugs that I corrected afterward). I did not pursue, because none of my cartridges are re-felted :twisted: .


May the FORTH be with you !
POLKa
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Chr$
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Re: General Microdrive woes

Post by Chr$ »

polka wrote:It's a long time since I used the microdrives, at some time I copied everything I owned to 720k floppies and recently, I transferred again everything to two CF cards for my TDI. But out of curiosity, I tried today my microdrives (on my first QL a JM bought in 1984), they seem to work ok (I only did some DIR commands and three COPY off my original ComputerOne FORTH cartridge - the one with three bugs that I corrected afterward). I did not pursue, because none of my cartridges are re-felted :twisted: .
I have all the mod cons too, TDI, vDrive, even a QNET connection to a Q68, but even if I don't actually use them to load/save they must still work at ALL times!

I actually do a lot of re-felting and mdv content imaging (dumps) so they do have to work for me.


https://QXL.WIN
Collector of QL related computers, accessories and QL games/software.
Ask me about felt pads - I can cut them to size and they have proved excellent for mdv data recovery.
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bwinkel67
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Re: General Microdrive woes

Post by bwinkel67 »

Chr$ wrote: And do the same thing trying various rollers to see it you can get it just right! I have some 3D printed rollers from a chap and they look good but to be honest I'm finding them a bit hit and miss (not for the first time). Just now a cleaned and turned-the-other-way original roller seemed much better, at least for reading a screen.
3D printed rollers actually work? It's not rubber but plastic...won't that slip?


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