On 2 Nov 2007 at 12:05, Curt @ Atari Museum wrote: Only as far as type and utility goes. A modern 3.5" drive is just as useful as an old Sony 0AD SS 3.5" drive, even if it only spins at 300 RPM. So I dumped my old Sony drives. But, for example, I have both the 2.88 and 6.4MB 5.25" Drivetec drives, even if there's nowhere to get formatted media for them, because they're the only thing that will read those diskettes. Cheers, Chuck

On 2 Nov 2007 at 23:59, Tony Duell wrote: I wonder if a DSHD 3.5" drive could simply be persuaded to spin the diskette twice as fast--they certainly run just fine at 360 RPM. I've never had to address the 2X issue (I'm more interested in reading disks from the old gear than restoring the old gear). Some of the old duplicator equipment used 2X and 4X drives, so there's another source for you. Or the FDC clock rate could be halved and a normal drive be used. Cheers, Chuck

On 3 Nov 2007 at 14:10, Ethan Dicks wrote: In the early days of the PC AT, many PC XT wanted the ability to handle the "new" 1.2MB media. This would have meant replacing the floppy controller for one that could do the tri-rate (250/300/500 Kbps) trick, but such beasts were expensive (I have a Sysgen Omnibridge that I use in my XT and it wasn't cheap). Someone (Fred might remember; my mind is too fuzzy right now) came out with a 1.2MB drive that would spin down to 180 RPM for high density and 300 RPM for double-density use. Pretty slick--no need to replace your FDC, but you get about one-quarter of the read head output voltage at the lower speed, so performance on the inner tracks wasn't wonderful. Cheers, Chuck

On 3 Nov 2007 at 8:43, Fred Cisin wrote: That's the one! I could well imagine that if it was a retrofitted standard 1.2MB drive that the ISV at 180 RPM might be pretty awful. Cheers, Chuck

Oh quite likely any of those things _could_ be done, and may have to be done sometime, but for now I'd ratehr keep the machines are original as possible and repair the existing drives. I am not one of these collectors who insists on every part having the right date code, but I don;t like changing the design _at all_. Most of tyhe time the problem is hardened grease on the eject mechanuism, which is easy to cure by taking the thing apart and cleaning up the parts. The problem comes if it's not been caught in time, but instead the upper (down) head has been caught in the disk shutter when the disk is ejected. Then it's time for a new head assembly, which you have to raid the same, but of course the head doesn't get damaged I've not had a fault on the main logic board yet. There is a mask-programmed microcontroller (not supriningly), but everything else is standard. I have had problems with the spindle motors in the doule-head models. One time the motor commutator chip died, it's a standard one used in VCRs, etc, so I could find a replacement. Another time a hall sensor failed, I raided one from the motor in a drive where I'd already taken the head carriage. I ahve never had to do a head alignemnt. I've replaced head assemblies. put the alignment disk it and found the CE patten to be well withing tolerance. According to the docs I have there were at least 3 special tools used for a full analignemt, one was a knob to fit on the stepper motor spindle and allowthe latter to be tuned by hand (easy to make). One was a tool like a screwdrier but with a pinion at the business end, used to turn the stepper motor. That's probably makable too, but I'd love to see an original one and count the teeth, etc. The last was a weight used to check the head compliance, I would love to borrow one of those and measure the mass. -tony