MDV2 Microdrive spinning slowly all the time.

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Plasticduck
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MDV2 Microdrive spinning slowly all the time.

Post by Plasticduck »

As the title suggests I have an issue with the microdrive.
Now I am new to the QL and have had a good look through the forum and can't find anything which cures my issue.
I purchased this QL about a month back from the car boot, visually it is in great condition.
It fires up and everything seems to work ok.
I have trawled the internet for advice regarding getting these to run well.
As such up to now I have fitted a new keyboard membrane as a few of the keys didn't respond and I have changed the capacitors.
This hasn't cured my problem though.
Microdrive 2 spins all the time, slowly, and the light is on very dimly.
I only have one cart, I have re-felted it, and have ordered some tested ones.
When I send either the format or dir command to either microdrive they spool up as intended but always come back as format failed.

If I try to dir with no cartridge in it reports not found as expected.
Now the failure to format may well be a bad cartridge hence I have ordered some tested ones.
I have tested TR6 as suggested in the service manual and that checks out fine.
It isn't the microdrive itself as swapping them over changes nothing.
Is there anything else obvious that causes this to happen or is it not a common fault and I am going to have to track it down myself.?

Many thanks for any suggestions, it really is a lovely unit, near mint, Issue 5 and I would love to keep it with the microdrives in place if possible.

James


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tofro
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Re: MDV2 Microdrive spinning slowly all the time.

Post by tofro »

Did I get that right, if you swap mdv1_ with mdv2_ it's still drive 2 that's spinning?

If yes, then I'd first try to remove mdv2_ completely and then test wether the remaining drive works without that disturbance.

TR6 (that you checked) and TR4 are responsible for drive 1 only if I read the schematics correctly. Have a look at TR7 and TR5 instead for drive 2, and probably D17. I think that section in the service manual confuses drive1 and 2.

Tobias


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Plasticduck
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Joined: Mon Feb 24, 2020 10:11 pm

Re: MDV2 Microdrive spinning slowly all the time.

Post by Plasticduck »

Thanks for the reply.
Yes swapping them gives the same result.
Just having a drive in position 2 gives the same and just having a drive in position 1 gives the same format failed result although I suspect cartridge.

Yes I just went off the service manual with regards transistor responsibility.
I will check out the ones you mention tomorrow, college tonight, and let you know.
I will also get a copy is the schematics and have a browse of that.

Many thanks again. James


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Chr$
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Re: MDV2 Microdrive spinning slowly all the time.

Post by Chr$ »

My MDV2_ is often a bit dodgy due to case warp and as a result, the cartridge not lining up properly (at least, that is my strong assumption). Have you tried accessing MDV2_ with the top of the case loose or just resting somewhere so that the keyboard ribbons fit and you can type in commands?


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Plasticduck
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Re: MDV2 Microdrive spinning slowly all the time.

Post by Plasticduck »

Just had a look at the schematic and you are right, it shows tr7 and tr5 for motor 2.
I will check them out tomorrow

With regards having it out of the case it makes no difference, mdv2 still wants to spin.
Sometimes it is getting so little power it is hardly turning and sending it a command brings it fully into life.


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Cristian
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Re: MDV2 Microdrive spinning slowly all the time.

Post by Cristian »

What about the mdv2 ribbon connector? Can you do a visual check without unplugging it?
Be careful, the ribbon connector pins are fragile: it may be a real pain to reinsert them!


Plasticduck
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Re: MDV2 Microdrive spinning slowly all the time.

Post by Plasticduck »

Yes the ribbon is fine and the problem manifests on either drive when plugged into the second slot, even with just that drive plugged in so is pretty much nailed on to be an issue on the main pcb.
You are right as well the cables are a real menace to plug back in.


Plasticduck
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Re: MDV2 Microdrive spinning slowly all the time.

Post by Plasticduck »

So TR7 and TR5 are fine. D17 is fine.
I am getting between 3 and 4 volts on pin 10 of the MDV2 connector all the time, 0v on pin 10 of the MDV1 connector as it should be.
Looking at the schematic and with my limited knowledge I can't see much else that it could be as the circuits that power each respective motor seem fairly simple.
I only had limited time after college to test a few components so need to have a probe about tomorrow.


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tofro
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Re: MDV2 Microdrive spinning slowly all the time.

Post by tofro »

Plasticduck wrote:So TR7 and TR5 are fine. D17 is fine.
Not questioning your methods, but, how do you detect "is fine"?

From what you describe, the motor control circuit is switching when it should, and not switching when it should, just has major leak current when switched off. This could well pass as good depending on your methods.

Other than that, (if the transistor is really not the issue), you can check the resistors around TR7 - The fault must be somewhere there.

Tobias


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Plasticduck
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Re: MDV2 Microdrive spinning slowly all the time.

Post by Plasticduck »

I tested them both in and out of circuit with a multimeter and also out of circuit with one of these chinese component tester jobbies.
I replaced tr4 and tr5 anyway but had no ZTX551's for tr7 and tr6.
I swapped 7 and 6 over but that made no difference.
I have been this morning to the local supplier and bought some ZTX551's so will replace them anyway, cheap as chips.
Both D17 and D16 checked out but again I replaced them anyway as when they are out it is as easy to fit new back in.
I have very limited time during the week to actually do anything with it but next my plan is to have a decent probe about and see where this voltage is actually from
coming from, maybe remove a few components and see where it originates.
It was there before I recapped the machine otherwise I would be thinking solder splash.
Will let you know how I get on.
Thanks again. James


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