The Sinclair QL Forum

I put a photo with the Serial Number.

So It can help to solve the mistery?

On further research, I found this which should nicely solve your problem: http://www.ebay.com/itm/Sinclair-ZX-Spe ... SwO~hXIJMl

Swapping wires 3 and 2 on the ribbon cable between the two boards should allow you to reverse the order of connection and use them ascending to the right. Solder side pin 4 is the pin that carries the location information, which is amended by the ULA. All the other pins pass through.

Check out this schematic

Checked my ZX drives and found a slightly later one (if they were numbered sequentially): Doesn't format or save unfortunately. Resistor values are r4=150/r5=180 as expected.

Hi Charles, Simone,

Very interesting findings, I wish to fiddle with resistors as well, but I have only a single Speccy MD unit.
I was possibly close last year, when building `mPort', but again electronics I usually learn from you QL lads here.

Tomas

Hi,

I have 3 External ZX Microdrives, which came from a ZX Spectrums I purchased as a job lot.

" ZX MIcrodrives are joined with the plastic plate and expansion connector, each drive has a Serial Number of:

04-082935
04-081725

And a Single ZX Microdrive with a serial number of:

T-I12961

Does anyone know if the serial number has a bearing on QL compatibility.

I was going to remove the microdrive and install a QL-SD card, placing the unit on the top QL over the internal microdrives.

Dave wrote:On further research, I found this which should nicely solve your problem: http://www.ebay.com/itm/Sinclair-ZX-Spe ... SwO~hXIJMl

Swapping wires 3 and 2 on the ribbon cable between the two boards should allow you to reverse the order of connection and use them ascending to the right. Solder side pin 4 is the pin that carries the location information, which is amended by the ULA. All the other pins pass through.

Check out this schematic

Hi Dave,

Could a jumper be installed so that the microdrive could be configurable as MDV3 or MDV4

I will have a look on at this on my dual ZX Microdrive units.

But how many external MDVs can be supported on the EC1 external Microdrive expansion interface on the QL?

Doesn't format or save unfortunately. Resistor values are r4=150/r5=180 as expected.

What tolerance are the resistors? If they were 10% tolerance ones which Ive found in a few 80s devices thats actually quite a wide range of values.

Even 5% is pretty wide!

G

Hi Derek,

Mine is 07-127762, not sure what resistors values it has. does not format QL attached.

Tomas

tcat wrote:Hi Derek,

Mine is 07-127762, not sure what resistors values it has. does not format QL attached.

Tomas

So a unit that format and write correctly is very rare.

Ehm...I think that this Speccy unit was one from QL mounted on the case of the ZX one...

While the PCBs are very different between the Speccy and QL the schematics are functionally identical. Unless the Speccy and QL devices use different ULAs, the resister values and possibly head resistances might be the only differences.

In theory, the Spectrum can support 8 microdrives, and the QL already having 2 could support 6 more.