After many months' fruitless attempts to fix the broken floppy drives on my Amstrad PCW 8512, I am pleased to say that I have done it - and HxC Floppy Emulator brought my PCW to life again!
Since I am very long-sighted (i.e. everything close is blurry), building a 26-to-34-pin adaptor was a very
difficult task. In the end, I found that it was easier to use a PC motherboard printer port cable, a 25-way D plug and an old floppy drive cable. Does anyone know whether I can purchase one of these 26-to-34-pin floppy adaptors, ready-made, please? This is for future projects.
With the PCW's floppy drive cable almost broken, I was only able to use one of the drive plugs. I soldered two 26-way PCB headers back-to-back, plugged a motherboard parallel port cable into this, and then attached this to the back of the PCW (see photo). The wiring of the DB25 plug turned out to be rather strange, with all of the PCW's evenly-numbered disk pins connecting to pins 1-13, and pins 14-25 connecting to GND. Until I tested the cable, I thought that pin 26 (READY) was not connected to the DB25 because there were only 25 pins - but READY turned out to be on pin 13 because pins 1-13 carry the PCW pins 2, 6, 4, 8, 10, 12 (yes, in that order).. all the way up to pin 26 (14 on the DB25), and then pins 15-25 of the DB25 are all GND. I tested the pinout several times, having 'smoked' a couple of floppy drives by connecting them up incorrectly, before.
Attached are a few photos of the working system. I used the Linux port of the HxC software, and I am using the USB HxC emulator (unfortunately, I cannot afford an SD-based one, yet). I've recently ported the software to run on my Nokia N800, so it's not reliant on a big computer. See http://brooknet.no-ip.com/~lex/public/N800_HxC
if you are interested.
The difficult parts of the project - apart from repeatedly opening the PCW - were the issues caused by the PCW's chassis floating at approximately 85V AC. I am convinced that this was responsible for the blowing-up of the aforementioned 3.5-inch floppy drives, and I didn't want the same fate to befall the expensive HxC interface. Thus, in the photo, you'll see lots of hacked-on earth cables (green and yellow) leading away from the computer. These are connected to the chassis of the computer, where the motherboard is mounted. To avoid a direct path to earth, I grounded this line through a 1/4W 270-ohm resistor, and it works pretty well - after the ground line was attached, the ground voltage dropped to 0.8V, which is preferred to 85V!
Any comments about what I did wrong (erm.. or what I did right - if anything) are welcome. Additional: the yellow stuff sticking out of the DB25 socket is PVC tape (I don't have any epoxy adhesive).