exxos's Atari, Amiga & retro forum

stephen_usher wrote: 02 Oct 2021 16:58 I'd remove the rubber and just sand the surface to make it pretty rough myself. Are you sure that the belt that you're using isn't too long?

I had already tried to sand the surface and it didn't work. Of course as you hinted, the rubber may be too thick and changing the gear ratio. The belt is the original that came with the drive, and as I haven't been able to find any documentation on this particular drive so I have no way of knowing if it's correct.

The original belt's possibly stretched a bit. You may be able to rejuvenate it a bit with a soak in IPA for a few minutes.

stephen_usher wrote: 02 Oct 2021 20:23 The original belt's possibly stretched a bit. You may be able to rejuvenate it a bit with a soak in IPA for a few minutes.

The motor has multiple positions to allow for belt stretch, so I have tried adjusting. I'll consider trying the IPA trick (I've cleaned but not soaked it with IPA), but it is fabric reinforced, so I'd hope stretch would be minimal, though you never know.

Since the spindle is something I can do now I will probably revisit, but it's really tight at just 3.2mm wide, so not easy to scuff up for abetter grip. If the thing was knurled from the factory then it wouldn't be an issue.

The other problem is that because of the cable routing, you need to desolder from the motor control board to be able to get the motor out to work on. I either need to make some sort of connector to allow easy removal, which is fine, or see how much leeway I have with the motor board loose.

I think the problem for now is definitely one of drive, as now it does actually spin the disk without slipping, it does register on the Locksmith tester, which it didn't when the belt was slipping. None of the belts I've been able to get have been suitable thus far, they are too stretchy.

I guess I'll figure it out, but at least feel like it's some sort of progress.

I think the logic is probably ok too as running some of the other Locksmith tests exercises the head and it seems to move correctly.

@rubber_jonnie Maybe you need some chip music to keep your company whilst you fix that drive?

http://fr3nch.t0uch.free.fr

PhilC wrote: 03 Oct 2021 15:13 @rubber_jonnie Maybe you need some chip music to keep your company whilst you fix that drive?

http://fr3nch.t0uch.free.fr

Lol, funnily enough I had been listening to some SID tunes earlier as my SD2IEC arrived and I was playing with it. I was playing that other tracker yesterday too through the Mockingboard :)

WRT the Seltron, I managed to remove the rubber and scuff up the spindle, plus move the motor position enough for decent tension just now, but guess what? The speed has now dropped off the bottom of the scale on the locksmith, so I think the problem isn't just one of drive, which it now has, it ratios.

Yesterday I think I had too much runner round the spindle, so it was driving it too fast. Now with no rubber, but enough grip, it is too slow and the speed adjustment isn't enough. So I think I need to try and get just a single thin layer of rubber onto the spindle, unlike the amount I had on yesterday, which was too much and took the ratio the other direction.

Meh!!

@rubber_jonnie good luck with that.
I know it sounds a bizarre suggestion. Do you have any rubber gloves under the sink? they might be thin enough for a couple of layers if necessary.

PhilC wrote: 03 Oct 2021 16:49 @rubber_jonnie good luck with that.
I know it sounds a bizarre suggestion. Do you have any rubber gloves under the sink? they might be thin enough for a couple of layers if necessary.

I also tried moving the motor today, and was able to get enough tension for just the brass spindle to drive it, but it was too slow again. Gahhhhh!!

So I managed to get a single thin layer onto the spindle and it's too fast again!! WTF.

I checked the pot that controls motor speed and it's 0-20K, so I have tried adding in some resistance to increase the overall total, and it has made some difference, in that when I adjust the pot, I get movement on the Locksmith speed tester, but it is so sensitive it drops down to too slow at the hint of an adjustment!!

The speed also starts off slower, even if the pot is all the way off now, so I know the resistors I added are doing something.

It all feels like progress, but what's really annoying is the lack of any schematics make it a little hard to figure (With my limited electronics skill).

There is a Sony chip on the driver board that may be relevant, so I'll go and look that up, see if it is a speed controller, and if so if there are any examples of how it's used.

It may give explain values for the pot, and given the only other function of this board is the write protect logic, I think the cip must be some sort of motor controller. I shall go have a look.

@rubber_jonnie sounds like a multi turn pot may help?

PhilC wrote: 03 Oct 2021 18:34 @rubber_jonnie sounds like a multi turn pot may help?

I just found a little snippet of data on the CX065B and it shows a 50K pot, so may just order one and see what happens!

EDIT: just ordered some 50K multi turn pots :)

Ok, so first opportunity I had was today, due to parental visits, car services etc to fit one of the 50K pots to the Seltron FDD.

I ran up Locksmith and used the disk speed test to get a feel for how things are, and after tweaking the pot a little, as all the readings were over on the fast side of the chart, I'm getting this now:




This is definitely progress, because whilst the readings should all be somewhere down the middle, it is at least swinging between too fast and too slow with readings now in the mid parts of the fast and slow sides, somewhere it's never been before.

I can do some additional operations in Locksmith that weren't working before, so it's looking more promising than it has in a while.