modelrail.otenko Trains, computers, vintage, retro, model railways… the lot…

Amstrad CPC6128 – Repairing the internal floppy drive

The internal drives in these machines need their own separate 12v supply. It's really quite a strange setup... as it means the power supply needs a male (positive on the inside) 5v DC jack and a female (positive on the outside) DC socket to get the machine up and running.

It all makes sense once you realise that the power was supplied by the monitor that came with the set. And since you don't want want the user to be able to get the plugs in the wrong order, having them oppositely-sexed means that there's only one-way-round that they can be connected... unless you try to connect the devices to themselves?

Anyway... I built the required power setup in the prevous post. This time around I actually have a set of strangely-sized Amstrad 3" floppies to test!

I bit the bullet and just tried to read the disks as soon as I got them... because, hey, sometimes things just work... Of course, no dice; it was either "no disc present" or "failed to read" each time. What next? Time to pull the thing apart! I really should've taken photos when I first did this as the amount of ... insect (I think?) debris inside the machine was intense. There were quite a few of either ant, moth or some other cocooning insect homes installed around the motherboard and, as expected, right inside the floppy chassis too. These things seemed to like to be near the warmer components.

There was also a very thick and protective layer of dust. The entire machine was pulled apart and 24hours were spent cleaning and drying. Again, I should've taken photos... but I was too scared to move everything on to the workbench. I didn't want a biohazard scene to break out. A lot of soap-suds later and the machine came up much nicer, but still had a pretty mottled outer-case.

Anyway, back to the floppy drive again. The discs weren't reading... so I watched them try to work whilst powered up. The head was happily scanning through the tracks, but the disc wasn't spinning. Turned out to be the age-old totally-trashed-drive-belt trick. Actually, when I first opened the case I should've realised that the 10mm x 5mm shards of black plastic (of which the texture should've been rubber) were chunks of the belt. They were actually so solid that I didn't recognise that they could've ever been elastic or soft!

Yup, those chunks above are the remnants of the belt. What to do? You could go on eBay and find a legit belt... or you could dig in your stationary draw for something like this.

And then, well, just undo all the screws on the underside of the drive, disconnect a cable or two and fit a rubber band. Be careful not to damage the band on sharp edges when you install it as you'll just be creating a weak-spot which'll tear when you least expect it.

Put everything back the way you found it and give it a go. I managed to get past the "no disc found" errors... but I still couldn't list a directory structure. I popped the disc back out and wiped down the head (there's a single-sided head in the drive, but the disks are double and need to be flipped) with alcohol wipes. No luck... but something occurred to me; there was a lot of play in the part of plastic that pushed the disc down onto the head... which meant that it wasn't actually properly being pressed down?

I gently pressed down on the metal plate that the disc actually sits on, just to see if there'd be better contact with the head, of which is under the inserted disc. Damn! It worked! I had no idea how to run LOGO3.COM, but the directory was there, printed in all its glory.

So, not enough downward force once the disc is inserted... how to fix? There happens to be a spring on either side of the 'floating' part of the chassis that the disc is supported on. I assumed that these springs were life-expired and weren't pulling down as hard as they should be. Probably explains why the disc doesn't 'click' in when you insert it either... it goes in and floats around.

Thanks to Jaycar, I purchased a box of springs. Actually, further thanks to Jaycar... they were free... as I received an AUD$25.00 giftcard in the mail for christmas due to my shopping last year!

Finding matchingly-sized springs was easy enough and installing them was pretty straight forward... just use tweezers to hook the inner loop.

From here, the 'click' was intense. Powering it all back up got me the following...

Snap. Just works(tm). Now... how do I even run Logo?

Nope... After a little googlin', turns out that it needs to be run from the CPM operating system... which is on the disk? Or something...

Getting somewhere...

And then... I have no idea how to use logo...

But win! I now have both an internal and external drive!