Microdrive Unit Design

[RWAP]

I had a bit of a sort through my microdrive units yesterday and have just been getting another QL up and running.

I decided to use some of the non-keyed microdrive units (ie. they have straight edges, not the jigsaw pieces which seem to appear on most units).

Having gone through several drives to get two working units, I was pleasantly surprised.

FORMAT mdv1_

produces up to 231/233 sectors

Compare that to the other microdrive units, which tend to return 218/222 sectors as a maximum.

mdv2_ gives slightly lower results, but it does appear that there is a difference between the keyed and non-keyed units.

I wonder which were the earlier ones?

[Mr_Navigator]

Pics?

[RWAP]

First the more common (at least in Europe) microdrive unit with the two keys on the edge:

[RWAP]

Now the less common microdrive unit with straight edges - note the extra red wire on the PCB - I have seen the one in a plastic sleeve on some of the units with 2 keys...

[RWAP]

Finally the very rare unit with just one keying piece - I actually have two of these, so will have to try them in a QL some time... (the keying piece is bigger than the one with 2 keys)

[Tom Phobos]

Nice I'll check out what type of drives are built into my german QL. Actually i only formatted one cart in the drive. It was empty, the first formatting attempts returned "format error". After a successful format it now has 202 sectors.

[Ralf R.]

Having gone through several drives to get two working units, I was pleasantly surprised.

FORMAT mdv1_

produces up to 231/233 sectors

Compare that to the other microdrive units, which tend to return 218/222 sectors as a maximum.

When I once built my (long non-existent) "QL-T", a non-PC desktop case with one mdv, I came across, that putting an diode in the drive_select lets you use one mdv for both 1 and 2.

And....making the motor a bit faster (I think there was a potentiometer on the PCB) gives more sectors. So I think, one of your mdv is running a bit faster than the other. I was able to get 235 sectors, but had not used this speed.

[chriskgnr]

where on the pcb is that potentiometer?

[RWAP]

And....making the motor a bit faster (I think there was a potentiometer on the PCB) gives more sectors. So I think, one of your mdv is running a bit faster than the other. I was able to get 235 sectors, but had not used this speed.

Yes I guess that for some reason, the microdrive units with straight edges run at a different speed - although they can still read/write cartridges formatted on the ones with the keyed edges.

I have tried two microdrive units with the straight edges and both give this higher number of sectors.

I have a feeling that these were used in the early QLs but then maybe for reliability, they slowed down the motor and used the keyed system to identify the newer version?

[Cristian]

And....making the motor a bit faster (I think there was a potentiometer on the PCB) gives more sectors.

This looks illogical for me. If the tape is faster the sectors should be larger, am I wrong?