Micro drive continuously spinning

[Derek_Stewart]

Hi,

Before you start desoldering chip from the QL, please look at the obvious, clean all the moving parts, reseat the QL main chips on the motherboard, clean the microdrive cable connection.

In variably the problem may be a mechanical issue or dirty connections.

Personally, I would get a Disk Inteface with onboard memory and look into a QL-SD and/or vDriveQL.

With regards to the vDriveQL, I think due to the Covid-19 issue, Charles is not selling at present and the QL-SD status seems unknown, I would like to buy an internal QL-SD unit.

I may have to make my own.

[Gbrigden]

Hi,
That's good advice. I'm not so great with soldering and would avoid it if I can.

I will try out the dismantle, reseating etc and see if that helps. I would like to stop the motors from spinning though so if I could find the cable that prevents this it would be great.

I have a trump card on its way so I will have a disk interface and I have used gotek emulator on other machines so I will go that route for sure. Just would be nice to have the micro drives working so I could load the software I do have.

Will def look to get the QL-sd when I can though. Looks like a great product as does the vDrive.

As ever, thank you for your help

[bwinkel67]

Hi,

I own a vDrive and love it. It's pretty clever and I believe the QL doesn't actually know about it when plugged in since it basically emulates an external MDV. The downside is it's a tad bit slow as I think it needs to be the speed of the original MDVs so the QL can read the data off of it. So no speed gains but also no failures . The basic vDrive only gives you MDV3 though MDV8 but if you install a separate product, vMap, you can also get MDV1 and MDV2 (I don't own vMap).

It comes with software (in ROM on vDrive) that you can load into RAM as a boot file to manage the SD card on the QDOS command line, though I found it was easier to just initialize the SD card using that software and then figured out the text format of the CFG file that maps MDV3 - MDV8 and then just edit it in Windows with Notepad. You can create a whole set of "banks" that creates multiple MDV3-MDV8 mappings and then, if the boot file is loaded, you can switch banks on the fly. vDrive makes swapping data between the QL and a PC/Mac/Linux system a breeze...I use an emulator in Windows to convert vDrive data though there are plenty of ways to do that.

[Gbrigden]

Thanks for the information.

I will go with an SD solution at some point as I have got such media working on the BBC Micro and the Atari (800 & ST).

I have had a chance to tinker with the QL this afternoon and have got some where. After cleaning all I could see, dusting, cleaning heads, reseating chips etc, I found that removing the drives, putting No. 2 in No. 1 place I didn't get the always spinning issue.

So I reconnected the keyboard, and monitor and yup F1 and after a slight buzz all seems well. Cartridge in and dir mdv1_ and the drive can to life. I was able to get results, and format a cartridge too.

I did place drive 1 back into the second position but that caused the motors to spin on power up and back to square one. Removing the faulty drive and all is OK.

So for now I have one drive working and the other disconnected for now. May be I can put a QL_SD in its place or replace/repair the fault drive.

Thanks again for your help in this.

[martyn_hill]

Hi Gary

That is good news!

Given the shared nature of the MDV bus, one flaky drive can be expected to interfere with another, otherwise good unit, so your latest results make sense.

Just for interest, we could infer from your results the following potential situation:

1. The ULA of (originally) MDV#1 is causing its COMMS-OUT pin to float/stick high, rather than act as it should as a latched bit, triggered by COMMS-CLK/COMMS-IN from the ZX8302 ULA - enabling its own power-circuit.

2. As COMMS-OUT of ULA #1 feeds COMMS-IN of ULA of (originally) MDV#2, the moment a positive-going COMMS-CLK appears from the ZX8302, MDV#2 will also be enabled.

3. As the first thing the ROM does in the set-up of the ZX8302 shortly after the RAM test is to 'clock-through' a single bit on COMMS-OUT 8-times - meant to disable ALL MDVs at startup - with the otherwise working MDV#2 seeing COMMS-IN permanently active (due to the faulty COMMS-OUT of MDV#1), BOTH drives will enable their power-circuits.

4. With a working ULA/MDV#2 in slot#1 instead, it is no longer affected by the defective COMMS-OUT of ULA#1 (but instead, any external MDV units added - there is an MDV expansion port available for this - would be affected like MDV#2 was.)

Anyway, if you do manage to acquire by some means a QL-SD unit, then replacing the faulty MDV unit with it makes good sense, giving the best of both worlds.

I believe that Marcel Kilgus is currently working on a ROM-port variant of the QL-SD interface (the original QL-SD sits in place of one of the MDVs) - check out his blog on the project here: https://www.kilgus.net/2020/03/28/ql-sd ... arly-days/

Good luck!

[Gbrigden]

Many thanks for the response and the detail there in. A little over my head at the moment but very interesting read.

So to fix the duff MDrive, will it be a case of replacing its ULA?

I did see the work being done on the rom variant and that looks interesting.

Thanks

[martyn_hill]

Hi again Gary

So to fix the duff MDrive, will it be a case of replacing its ULA?

Whilst the cause of this MDV failure is likely to be the ULA, I wouldn't neccessarily recommend trying the replacement yourself. Much easier to find an entire MDV replacement, that come up from time to time. You might want to check-in with Rich Mellor of RWAP Services in case he has a unit that isn't already listed on his SellMyRetro site.

[Gbrigden]

Many thanks Martyn
I'll see what I can find.

[Chr$]

Hi again Gary

So to fix the duff MDrive, will it be a case of replacing its ULA?

Whilst the cause of this MDV failure is likely to be the ULA, I wouldn't neccessarily recommend trying the replacement yourself. Much easier to find an entire MDV replacement, that come up from time to time. You might want to check-in with Rich Mellor of RWAP Services in case he has a unit that isn't already listed on his SellMyRetro site.

They are indeed a pain to do because you have to de-solder the read/write head. I've changed 3 MD ULA's this year and it is amazingly satisfying when they work again. I deliberately added a socket to one, so that I can use it to test unknown/problem ULAs - only disadvantage is that the whole lot no longer fits where it needs to fit (for that one it was a ZX Microdrive unit).

OP: You're lucky to get one going though, that's probably all you'll need these days, especially as you're upgrading. It's just something to read carts if you ever need to.

Make sure you re-felt the carts you have though, or they are very likely to fail.

[bwinkel67]

I've seen that if you are good at soldering and have a heat gun (is that what they are called) that you can desolder chips from the top side. Anyone ever try this with a bad microdrive. I have a spare and some parts from another (including motor) so I could see how hard it would be (no sure if the spare is broken).

Btw, how could I plug my spare in as a 3rd microdrive? Do you need a second daughter board or is it just matching up the cable to the side slot pin outs?