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Kaypro 4: Drives not reading when cold.

Joined
Mar 3, 2015
Messages
21
Hi everyone.

i've currently got a Kaypro 4 on the bench which seems to be a little un co operative when starting from cold. When I insert the boot disk, the A drive is spinning. Most of the time I will just hear the read/write head trying to read track 0. Other times i'll hear no head movement at all. After a few minutes of letting the drive spin it will read okay.

I was thinking this might be a dirty head / lubrication issue. Especially since the fault is only present when the drive has not been used for a number of hours.

Any second opinions on this? Also what's the best type of silicon grease to use on the drive rails (I havent actually worked on many 5.25" drives before). I'm also assuming that i can use some sewing machine oil on the disk-spin and stepper motors (if I am able to get access to them).

Thanks!
 
You didn't mention the Manufacture's name of the Floppy Drive(s). If they use Carriage Rods with a Head assembly that glides on the Carriage Rods,
use Dri-Slide (a Motorcycle Cable Lubricant) on the Carriage Rods. Dri-Slide is available at most Motorcycle shops and it will only require 3 or 4
drops of the lubricant. A can will last you a lifetime. It's also good for lubricating Scanner rails. I typically wipe the Carriage Rods with a Cotton
Swab dipped in Alcohol. When the Alcohol is dry lube the rails, and very slowly and carefully move the Head Carriage Assembly full travel.

Grease and heavy lubricants attract dirt & dust, so do not use them on 5.25" Drives. Some 3.5" floppy use a screw assembly for head positioner
and are lubricated with heavy grease.

In the last 40 years I've never had to lube the cone/centering assembly on any 5.25" floppy drive. Likewise, I've not lubricated any stepper motors that have
sealed bearings, but your mileage may vary. I did have to track down the problem with a Stepper Motor Winding that had a Cold Solder Joint.

As for the cold start problem, I'd check the Power Supply Voltages, and connections. Some Power supplies have had cold solder joints (Tandy)
on the PCB's. Also check that the Floppy Head(s) are clean and not coated with brown oxide. Carefully and easily clean those with Alcohol on a Cotton Swab.

Larry
 
I had the same problem with my Kaypro 4/83 with the full-height floppy drives. When cold, the drives were very flaky. Once things warmed up (temperature-wise), they worked fine.

IHMO, you should replace the drives with a floppy emulator. When I did that on my Kaypros, they became so much nicer to use.

5.25" media is getting more scarce. No more is being made. The latest used disks that I got had a format failure rate of about 1 out of 3. At some point (and that point seems to be getting closer every day), the media will have worn out.
Besides, most stuff on the Internet comes in the form of floppy images, which are much easier to use when you have a floppy emulator.
 
You didn't mention the Manufacture's name of the Floppy Drive(s). If they use Carriage Rods with a Head assembly that glides on the Carriage Rods,
use Dri-Slide (a Motorcycle Cable Lubricant) on the Carriage Rods. Dri-Slide is available at most Motorcycle shops and it will only require 3 or 4
drops of the lubricant. A can will last you a lifetime. It's also good for lubricating Scanner rails. I typically wipe the Carriage Rods with a Cotton
Swab dipped in Alcohol. When the Alcohol is dry lube the rails, and very slowly and carefully move the Head Carriage Assembly full travel.

Grease and heavy lubricants attract dirt & dust, so do not use them on 5.25" Drives. Some 3.5" floppy use a screw assembly for head positioner
and are lubricated with heavy grease.

In the last 40 years I've never had to lube the cone/centering assembly on any 5.25" floppy drive. Likewise, I've not lubricated any stepper motors that have
sealed bearings, but your mileage may vary. I did have to track down the problem with a Stepper Motor Winding that had a Cold Solder Joint.

As for the cold start problem, I'd check the Power Supply Voltages, and connections. Some Power supplies have had cold solder joints (Tandy)
on the PCB's. Also check that the Floppy Head(s) are clean and not coated with brown oxide. Carefully and easily clean those with Alcohol on a Cotton Swab.

Larry

Thanks i'll give that a go. I may check all the caps in the power supply while i'm at it too since most computers of this age i've dealt with tend to have problems in that area.
 
I had the same problem with my Kaypro 4/83 with the full-height floppy drives. When cold, the drives were very flaky. Once things warmed up (temperature-wise), they worked fine.

IHMO, you should replace the drives with a floppy emulator. When I did that on my Kaypros, they became so much nicer to use.

5.25" media is getting more scarce. No more is being made. The latest used disks that I got had a format failure rate of about 1 out of 3. At some point (and that point seems to be getting closer every day), the media will have worn out.
Besides, most stuff on the Internet comes in the form of floppy images, which are much easier to use when you have a floppy emulator.

They have their uses, but floppy emulators take away too much of the experience for me ;)
 
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