Microdrive/vDrive woes

[Chain-Q]

Hi guys,

Some of you might remember me, I was the guy who about 2 years ago, at a QLvember decided to introduce a Sinclair QL target for free Free Pascal Compiler. Back then I had no QL hardware, nor any experience with it, but sounded fun. I did all the work in emulators, mainly QemuLator on my MacBook. But then earlier this year, I decided to buy myself a QL, finally. That's where the problems began.

So long story short, I bought a QL from somewhere Italy off evilBay, then I bought a bunch of expansions for it, among others, a vDrive. But I just collected everything in storage, as I was very busy through the year with work and other projects, so I was like "I'll just chill with the QL after Christmas". Well, here we are.

I knew the machine was working, because I tested it briefly after receiving it. And initially the MDV1 internal microdrive worked too, but not MDV2. So now I disassembled the whole thing, and noticed that MDV2 was not plugged in correctly. One pin of the drive-cable-from-hell wasn't in the mainboard-socket-from-hell, but just dangling to the side. Wasn't me, but whoever was in there before me. So I corrected that, meanwhile also installing the vMap I bought. Since I ran out of microdrive tapes of intact felt very quickly, I could only test if the right drive was addressed, by issuing the "dir MDV?_" command and observing "Not found". And indeed, the MDV1_ -> not found MDV2_ -> not found (and the right drive was lit), MDV3_ ... the vDrive lit up, went red and then got stuck. Endlessly trying to load. Well, it fails after 10 minutes, and I get back the prompt. Not found. Not good.

So ever since I've been struggling with this, just trying to get the vDrive working.
- I tried swapping the two internal microdrives - to no avail
- I tried connecting both internal ones as MDV1 - nope
- I tried just installing the vMap alone, so the external drive can be remapped - but still no workie, not even as MDV3_
- I also tried the "bypass method", just connecting Pin1 of the MDV1 socket to Pin2 of the MDV2 socket, then the external vDrive tries to boot even and acts as MDV1, but it's still stuck in an endless loading loop, and eventually it times out.
- Tried both with Minerva ROM and the original JM ROMs in the machine. - Still nothing, same behavior.
- I noticed that the machine sometimes crashed, when I touched the 68008, so I first cleaned its socket with contact cleaner + IPA (a brown bad looking socket-from-hell), and also tried with another 68008 I had at hand - no change. (But at least the random crashes are gone, fingers crossed?)

Also, probably important info, that MDV2 actually exhibits the behavior of the vDrive, when I put in a microdrive tape that cannot be read. It just tries to read... and read... and read... While MDV1 itself at least times out fast, and says, not found. So I'm semi sure it's something on the mainboard and not on the vDrive.

Oh, additional fun fact: someone swapped the 4164 chips on this mainboard to 41256, and added the 74ls257 address decoding hack, so it has 512KB RAM. Which is great, I guess, but I now cannot use the 512KB RAM expansion I bought for it - that would have provided 640KB. The board otherwise seems to be an Issue 5 board, I think, the case has the serial D12-097718.

Basically my question is, from the above description, can it be anything else than the 8302 ULA... Or does anyone see anything I might have missed, or what I'm holding wrong, or what else I can try or test. Thanks a lot!

[bwinkel67]

With micrdrives, you need to be sure the cartridges are properly felted and formatted. It wasn't clear from what you had done although you did say you initially tested MDV1 and it worked...how did it work? You formatted a cartridge, were able to write something on it and then read off it? Or did you just pop in an old cartridge and do a DIR and it worked? More information here on how it first worked and then stopped might be helpful.

So ignoring the microdrives for now, were you able to get vDrive to work at all? It seems like you immediately installed vMap. Did you try vDrive without vMap installed? Did that work?

[Derek_Stewart]

Hi,

The expansion expects 128K on the QL motherboard and the 512K ram expansion adds to the internal 129K ram, giving 640K.

The onboard 512K will clash with the 521K ram expansion.

To use the ram expansion, the 41256 ram chips may have be replaced by 4164 ram chips to give 128K plus the 512K ram expansion.

With regards to the vDrive, try cleaning the external Microdrive edge connector and make sure the microdrive cable to the vDrive is working correctly.

I have replacement Microdrive units available, tested to work with vDrive and Vmap.

Or even a replacement QL board.

[bwinkel67]

Oh, that's also a good point. Cleaning the heads with a cotton swab and some isopropyl alcohol can also improve read/write functions. It's usually the first thing I do when I get a consistent failure and on many occasions it fixes the problem.

P.S. because I can never remember the spelling:

Is there a difference between isopropyl alcohol and isopropanol?
They are the same chemical. Unfortunately there are many different naming conventions, this does lead to some confusion. So look for the two commonly used names Isopropanol Alcohol 70% or Isopropyl Alcohol 70%.