Kaypro XT Toshiba drives having intermittent faults and not working

I have a kaypro XT with two toshiba floppy drives (see photo for label) i can find no documentation for them.

the main issue is that both will intermittently not work, both at the same time i think?. when they do work drive A will read the directory but if i try to run something i get "sector not found reading drive A" the heads seem to move back and forth as if looking for something, head issues maybe? Drive B works just fine. I swapped the drives top to bottom and the problem follows the drive.
both drives have been serviced and are mechanically working fine. i was very careful cleaning the heads but i suppose i could have misaligned one. how can physically electrically test the heads, and check the alignment of them?

I have no idea what causes the intermittent fault, when that happens I just get "general failure reading drive" or "drive not ready". they started working again after using a cleaning disk and swapping the floppy cabe for the original one that worked before.
maybe just a dodgy connection for the intermittent problem?

I haven't found any information on those floppy drives on the internet yet.

It sounds like some of your Floppy's are shedding the oxide and making a deposit on the Read Head(s).
Best to listen for unusual sounds when the floppy's are rotating and if any are making funny noises
put them aside. Keeping the Head(s) clean isn't an easy job, but if you insert a good floppy into
the drive(s), there is a chance of destroying it as the floppy drives try to access it. So be cautious
as you can destroy good floppy's easily with dirty heads.

Larry

I have some new old stock floppys that are perfectly good, I have moved one of those disks back and forth between the good drive and the bad one multiple times and the good drive always reads the disk. i don't think the drive is damaging the disks. I do have a bunch of old grungy floppies that i did try to read a while back but mostly in the drive that works and not recently.
Is there another way of cleaning the heads other than using alcohol on a swab, i also used a cleaning disk a few times.
How could i test the heads to see if one is bad or not?

one thing i noticed is that these drives have a solenoid that lowers the heads down when the drive is accessing the disk. on the drive that works, it makes a nice sharp satisfying click noise. the drive that doesn't work makes more of a clunk and is louder than the good one. but as far as i can tell everything moves freely. does anyone know of a common failure point on this type of drive?

The central hub makes a bit of noise but it spins just fine. recently a piece of dried up rubber came off of the central hub, i'm not sure how they are constructed but could the central hub be out of alignment and cause an issue if something were to break apart?

theres been a development. I ran a cleaning disk in the bad drive a BUNCH of times, after that it started partially working, it will now load files from the directory. the wierd part is that it will only load one particuliar file from one particuliar disk. I cant format on that drive or copy files to it, or open any other files. could the heads still be dirty? they look spotless.
the other drive works just fine still with any of the disks.

One thing that comes to mind is the RPM of the Floppy Drive(s) needs to be 300 RPM.
I don't know if those Floppy drives have the hub ring that has the 50Hz and 60HZ
chart on them for setting the speed under a Fluorescent Light. You can always
look at the Index pulse, and trigger your O'Scope on a low going signal to see what
the Frequency is. F = 1 / Time

You really need an exploded view of the Floppy drive to see how the Hub is assembled and
what's involved.


Larry

The upper hub is a pretty simple assemby, there was a rubber washer that desintegrated and corroded the bearing on the upper hub. I was able to remove the upper hub and free up the bearing. it's soaking in evapo-rust now.

these drives do have the 50 and 60 HZ blocks on the motor, using a fluorescent light I can tell that they are both going the same speed.
after reassembling the drive with the stuck bearing it is no different and still loud. the bearing is molded into the hub so i guess i'll just have to deal with it.

I have swapped the drives from the A to the B position and the issue follows the grive. I have also swapped the logic board from the good drive to the bad one and it makes no change. this definitively proves that it is an issue with the drive mechanism itself, I am inclined to say the heads. I'll see if i can find a way to test the heads.

Well i figured it out. I used imagedisk to do an RPM test and they were both running about 20 rpm too fast. i don't know how one of the drives was working like that. I used an LED connected to a function generator at 60 HZ and set them to the right speed usind the factory speed marks on the bottom. and now they both work. to put the icing on the cake, i was able to replace the bad bearing.
Thanks for the help.

If you ever find any information on those Floppy Drives make sure you send it to bitsavers and archive.org.

I'm glad you figured it out.

Larry