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3.5 inch floppy drives - repair or not?

tingo

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The days where 3.5 inch floppy drives were easily available ended some years ago (at least here in Norway).
Today I tested a couple of motherboards as possible floppy imaging machines, using the excellent TestFDC program by Dave Dunfield.
Since I don't have the necessary cables for my 8 inch floppy drive yet, I tested with a 3.5 inch drive instead.

During that testing, I discovered that I have two non-working 3.5 inch floppy drives:
Panasonic JU-257A654P
Sony MPF920-E (E/131)

I haven't looked closely at the drives yet, to figure out what's wrong with them.
Should I repair the drives? Is it possible?
 
It depends on the drive. I think generic form 3.5" 1.44mb drives are still common enough that they aren't worth messing with, but oddball form-factor drives such as IBM PS/2 3.5" drives are increasingly uncommon and should be repaired.

Of course, you should check the simple stuff. Use a cleaning disk to clean the disk heads. Blow any dust out of the track zero sensor. Clean and re-grease the worm gear or whatever mechanism moves the head. Make sure the head moves and exercise it a bit. Inspect the cable connectors for damage, and look closely to see if there is an "A"/"B" switch and if there is, make sure it is set properly.

Also, don't forget to check those #$%#@$%$#@ cables. :)

There is only so much else that can be done on 3.5" drives. Some may have electrolytic capacitors that need replacement. Fixable, but a pain. Semiconductors/PCBs can be swapped between identical model drives, although it seemed like no two matched even back when they were new. But if the heads are borked then it is usually game over.

Still, if you have a dead 3.5" drive that you believe was a good model and was not too poorly stored, then you might hang on to it for the future.
 
I agree. Unless they are something other than the run-of-the-mill 1.44MB floppy drives, there are still enough out there.

I have a number of different drives on my site and I have about another 30 or so to add, when I get the time.

There are several specific drives that I have that can be converted to 720K only operation and I'm going to concentrate on doing that. I just converted a specific sub-type of a JU-257-xxxx to a 720K drive for a standalone analyzer for a company in British Columbia where it wouldn't accept a 1.44MB because of signal tests it ran at start-up.
 
My go-to 3.5 drive is the Samsung SFD-321B. Lots of ways to configure it.

But, since nobody makes floppy drives any longer, there are some things to consider when buying even NOS units. The foremost is grease. The oil leaches out and it gets stiff. Almost all 3.5" drives use a leadscrew-type positioner, so hardened grease in these can make the drive behave erratically. A little solvent and a toothbrush is all that's required to restore these drives to fresh new operation.

I'll use a little pure silicone lube (sort of a heavy oil) rather than grease on these.
 
PC 3.5" drives are still cheapish so I would not bother unless they are special (rare laptop drives with rubber belts, Panasonic drives with jumpers that can be used on systems like Amiga etc).
5.25" drives are not as common so I would either look into fixing them or keep them around until it is worth repairing them financially.

Amiga, auto inject apple, and IBM PS/2 drives should be repaired if possible since they are hard to find and there are no other options plus are worth some money in working condition.
 
Yes, I have some of the 321B units as well and, they are a good little 3-mode unit, but, unlike some others, they can't be locked into 1.0M mode, so, for the things I need them for, they don't work out.
There are some 3-mode drives that let you modify them for any one of, or any combination of, modes.
 
Are you sure about that? I've never had to do it, but I'm a bit skeptical on that claim.
I was surprised as well, but I think Druid may be right; still, nothing that a jumper (or cut trace,as the case may be) on the media detect switch won't fix.
 
OK, let's put it this way; some of the drives have information that allow you to do what I need to do (lock a drive into Mode 1) but most don't and just removing the HD sensor doesn't do it. Apparently, the DD mode (1) needs a high from the sensor (for some reason). I could tie that line high, and it might work, but, I really don't have time to experiment with it unless someone wants to buy one.

With some early Panasonic JU-257s, there is a row of slide switches along the back edge of the logic board that allows you to accomplish this very easily and some have nice little diagrams on the logic board that tell you how to do it.

In no case does any of it require messing with the HD detector.

The big problem is that I don't have any of the drives that I have the instructions for and I have a LOT of drives with no instructions. Everyone seems to build their drives differently, so there is no one-size-fits-all solution to faking up a 720K drive from a 1.44M drive, especially in devices that are smart enough to just format with the 720K parameters.
 
If you're really curious, I can post a photo of how to restrict the drive to 2D.

Personally, I use either FD235F or NEC FD1035 drives for that.
 
OK, let's put it this way; some of the drives have information that allow you to do what I need to do (lock a drive into Mode 1) but most don't and just removing the HD sensor doesn't do it.
If you can find a fixed or switch-selectable DD drive, great, but FWIW all the 1.44 drives I've ever worked with use switches instead of sensors, so it's pretty trivial to either cut or short a trace to lock them in DD mode.

With some early Panasonic JU-257s, there is a row of slide switches along the back edge of the logic board that allows you to accomplish this very easily and some have nice little diagrams on the logic board that tell you how to do it.
Some models without the switches use the same board, so you can install jumpers instead.

The big problem is that I don't have any of the drives that I have the instructions for and I have a LOT of drives with no instructions.
I'm familiar with that problem... ;-)

m
 
Some 3.5" HD drives (especially the earlier ones), used the so-called "PS/2" signaling, where the host called out the density. It could really be a problem because you'd get 1.44M data on 720K floppies--the system was blind. In the later years it got worse, as some PS/2s would use the same system for ED floppies, so you could get a 2.88M recording on a 720K floppy. Eventually IBM came to their senses, but I still occasionally have to drill a hole in a 720K floppy to read it.

Spec sheets can be very hard to find. Only recently, I came across the OEM manual for the Teac FD-235HG "3-mode" drives. Apparently, there was even a USB version of the 235HG with an added-on USB adapter board.
 
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