exxos's Atari, Amiga & retro forum

rubber_jonnie wrote: 25 May 2021 10:40

stephen_usher wrote: 25 May 2021 10:36 It's an early Sony special. Running at 600RPM.

The F2 uses bespoke JVC drives, again at 600RPM.

Oh joy. I presume though that there must be datasheets for it and it's possible to work out what it's trying to do, especially as you have working units.

I have a PDF of the service manual for the Sony drive. (Yes, they expected engineers to be able to field service floppy drives back then.) but unfortunately the main circuit board is a field replacable unit.

I can't even find any mention of JVC even making floppy drives on the Internet. Google has come up blank.

stephen_usher wrote: 25 May 2021 10:50

rubber_jonnie wrote: 25 May 2021 10:40

Oh joy. I presume though that there must be datasheets for it and it's possible to work out what it's trying to do, especially as you have working units.

I have a PDF of the service manual for the Sony drive. (Yes, they expected engineers to be able to field service floppy drives back then.) but unfortunately the main circuit board is a field replacable unit.

I can't even find any mention of JVC even making floppy drives on the Internet. Google has come up blank.

Back when I was a field engineer, the only PCB swap you did was a mainboard, floppies were just a module. What about the components on the drive PCB, or are there just too many parts to replace?

Do you have a model number for the JVC drive and I'll try my Google-Fu on it?

rubber_jonnie wrote: 25 May 2021 10:53

stephen_usher wrote: 25 May 2021 10:50

I have a PDF of the service manual for the Sony drive. (Yes, they expected engineers to be able to field service floppy drives back then.) but unfortunately the main circuit board is a field replacable unit.

I can't even find any mention of JVC even making floppy drives on the Internet. Google has come up blank.

Back when I was a field engineer, the only PCB swap you did was a mainboard, floppies were just a module. What about the components on the drive PCB, or are there just too many parts to replace?

Well, the Sony drive has a lot of DIP 74LS chips and one surface mount control chip in the centre of the board. Tracing signals the 74LS chips seem to be doing their thing so it's probably the controller chip gone a bit iffy. When I first tried the drive, before cleaning things, it did actually work. I think the switch cleaner might have done something bad.

rubber_jonnie wrote: 25 May 2021 10:53 Do you have a model number for the JVC drive and I'll try my Google-Fu on it?

I'd have to disassemble the F2 again to have a further look but I couldn't find a model number the last time I looked, merely a serial number, which was different on both drives. I may try swapping the controller boards and see how the fault migrates. Does stay with the board or with the guts of the drive?

The drives themselves have quite a strange head movement mechanism, it's not a worm drive connected to a stepper motor it's a steel(?) ribbon which wraps around a spindle connected to a stepper motor. To move the heads it winds/unwindws the steel ribbon.

stephen_usher wrote: 25 May 2021 11:02
I'd have to disassemble the F2 again to have a further look but I couldn't find a model number the last time I looked, merely a serial number, which was different on both drives. I may try swapping the controller boards and see how the fault migrates. Does stay with the board or with the guts of the drive?

The drives themselves have quite a strange head movement mechanism, it's not a worm drive connected to a stepper motor it's a steel(?) ribbon which wraps around a spindle connected to a stepper motor. To move the heads it winds/unwindws the steel ribbon.

If you're in the F2 it'd be interesting, but don't go pulling it apart on my account :)

Be interesting to know if the fault moves with the board, are they that similar you can do that?

With regards to the steel ribbon/stepper motor combo, I've seen that quite a few times on older FDDs, even on some older what you might call 'standard' 3 1/2" FDDs. I remember that it was common on 5 1/4" drives when I had PCs with those drives back in my 8086-386 days.

I actually think it is a very reliable mechanism, but it doesn't lend itself well to a compact form factor.

rubber_jonnie wrote: 25 May 2021 11:23

stephen_usher wrote: 25 May 2021 11:02
I'd have to disassemble the F2 again to have a further look but I couldn't find a model number the last time I looked, merely a serial number, which was different on both drives. I may try swapping the controller boards and see how the fault migrates. Does stay with the board or with the guts of the drive?

The drives themselves have quite a strange head movement mechanism, it's not a worm drive connected to a stepper motor it's a steel(?) ribbon which wraps around a spindle connected to a stepper motor. To move the heads it winds/unwindws the steel ribbon.

If you're in the F2 it'd be interesting, but don't go pulling it apart on my account :)

Be interesting to know if the fault moves with the board, are they that similar you can do that?

With regards to the steel ribbon/stepper motor combo, I've seen that quite a few times on older FDDs, even on some older what you might call 'standard' 3 1/2" FDDs. I remember that it was common on 5 1/4" drives when I had PCs with those drives back in my 8086-386 days.

I actually think it is a very reliable mechanism, but it doesn't lend itself well to a compact form factor.

The two drives in the F2 are the same. One of the drives doesn't read and write correctly, that's what I can test with the board swap. The Sony's very different. :-)

I noticed that the switch used in the JVC drive for determining if the drive is inserted is the same as in one of the Epson/Atari drives. I'll have to look up in the loft at the dead Chinons to see if they have the same. If so I can scavenge a switch from that.

Seeing as it's a bit quiet "at work" this morning I've quickly pulled the F2 apart. There is actually a model number, "MDP-40H".

Here's everything written on the drive:

Let's see what my Google-Fu comes up with.

Actually, I think that I've found the issue with this drive, the upper head gantry(?) is misaligned. If I push it firmly to the right (as you look from the front of the drive) before use, for a while it reads fine. I thought that it looked twisted a bit. The trouble is that it's all plastic so goodness knows why it's deformed slightly.

Oh! Bending down the left-side of the floppy frame has made it work. It was lifting the head slightly.

Good find!!!

And wow, I tried looking under JVC, JVC/Victor, Victor, and absolutely zilch!!

It has seemingly escaped the internet!!