The Sinclair QL Forum

bwinkel67 wrote:
3D printed rollers actually work? It's not rubber but plastic...won't that slip?

You can buy special elastic 3D printing filament that's close to rubber.

tofro wrote:

bwinkel67 wrote:
3D printed rollers actually work? It's not rubber but plastic...won't that slip?

You can buy special elastic 3D printing filament that's close to rubber.

Yes, that's right. They are rubbery. From my experience they seem to make the drive louder and just not as good as the original. I formatted the same cart today in a drive with a printed roller and got very high total sectors, and I think the total good sectors was 17 lower. The same cart formatted in another drive with an original roller yielded a more sensible approx 222 total sectors of which about 6 fewer were considered good. I'm not quite sure off the top of my head what that indicates... but it certainly doesn't seem right.

And generally reading/writing tends to be less reliable. I wonder if they may slip a bit on the shaft as they are slightly easier to push on than the originals.

If the tape head was misaligned, I would expect that the drive would work with cartridges that it formats. But the cartridge would not be interchangeable with another drive unit.

Another possible problem, is that the tape head has become magnetized. I don't know if the Microdrives can suffer from this. You can get tape head demagnetizers, But if you have one, you might try waving a Weller soldering gun over the heads.

https://www.vintage-radio.net/forum/sho ... hp?t=29127

Martin_Head wrote:If the tape head was misaligned, I would expect that the drive would work with cartridges that it formats. But the cartridge would not be interchangeable with another drive unit.

Another possible problem, is that the tape head has become magnetized. I don't know if the Microdrives can suffer from this. You can get tape head demagnetizers, But if you have one, you might try waving a Weller soldering gun over the heads.

https://www.vintage-radio.net/forum/sho ... hp?t=29127

Yes, I did have some behaviour like that with the formatting and reading, but it was inconsistent.... like a lot of things seem to be with mdvs! I think the head alignment played a role though as in the end I loosened the 2 screws that hold the board, removed the motor and removed a piece of stuck on rubber from the motor that was pushing the board outwards and the head slightly downwards. It seems much better now and I've loaded some original Psion mdvs, Steve Davis Snooker and Gwendoline and anything that doesn't work, also doesn't work on my main QL so I think I'm in business.

Bet I'll try it today and it'll be wrong again!

Chr$ wrote:

tofro wrote:

bwinkel67 wrote:
3D printed rollers actually work? It's not rubber but plastic...won't that slip?

You can buy special elastic 3D printing filament that's close to rubber.

Yes, that's right. They are rubbery. From my experience they seem to make the drive louder and just not as good as the original. I formatted the same cart today in a drive with a printed roller and got very high total sectors, and I think the total good sectors was 17 lower. The same cart formatted in another drive with an original roller yielded a more sensible approx 222 total sectors of which about 6 fewer were considered good. I'm not quite sure off the top of my head what that indicates... but it certainly doesn't seem right.

And generally reading/writing tends to be less reliable. I wonder if they may slip a bit on the shaft as they are slightly easier to push on than the originals.

I guess the 3D-printed rollers have a more uneven surface compared to the original ones (as 3D-Printing always "rasterizes" things). It might make sense to print them slightly oversize and grind them down with a lathe (or a lathe-like contraption) and some emery.

They are a bit rough looking...

If you look on the 3d printing forums, and youtubes - there are some techniques for 'smoothng' the surface chemically - using a large tin, some kitchen towels soaked in Acetone, and suspending the 3d printed object in the fumes (keep the lid on, and do this somewhere well ventilated) - Nail varnish remover should also work.

https://www.youtube.com/watch?v=6xFUNFG-UKE

Chr$ wrote:What kind of cap is DC28? Why does it have a DC prefix instead of just a C? I just wondered about that.

I think I've answered my own question here: The answer is that it's a normal capacitor, DC for de-coupling, as it goes across the +5v and the GND of the ULA (pins 9 and 12).