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Old 15 January 2014, 12:54   #1
Firestone
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TEAC FD-235F suddenly stopped reading disks

Hello everyone!

Just wanted to see if anyone could give me some technical information on how to track down the problem I recently got with one of my A1200s floppy disk drives.

The drive is as the topic says, a TEAC FD-235F drive originally mounted in a Commodore-version of the A1200.

Yesterday I mounted the Indivision AGA MKII to this machine and everything seemed fine. The machine boots from the CF-card perfectly and the flickerfixes does what it's supposed to do.

But the floppy drive suddenly won't read any disks anymore.
I had to remove the floppydrive to route the cable from the Indivision under the drive and out through the expansion-door near the mouse-port.
When I reassembled everything and mounted the floppydrive again I put the drive into place and mounted it with ONE screw (the one located near the accelerator trapdoor slot).

I tried to put in a disk, and it seemed to struggle spinning the disks, so I powered down the machine immidiately and removed the drive again.
Removed the screw and started the machine again. Now the disk is spinning fine. I can hear that everything clicks into place when the disk is inserted (and I can see it when the cover is off).

When there is no disk inside I can see and hear the head moving forward and backward these steps searching for a disk.

When I insert a disk the disk spins for a while while the heads just give these three "reading attempts" if you know what i mean. The same noice as if the disk was empty, and workbench gives me DF0:???? as long as the disk stays inserted.

Could I have damaged something when I tried to mount it? I really can't see what could have damaged it so badly that it should not be able to read any disks anymore, and everything else in the drive seems to work just fine.
Could the heads have been damaged or something during this?

I thought I was carefull when was inserting the screw temporarly, but probaly not carefull enough....

Of course I could just go on eBay and buy a new one, but that wouldn't be any fun, would it?
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Old 15 January 2014, 12:58   #2
demolition
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Does that drive have a visible flywheel underneath? If so, then maybe it rubbed against the cable that you routed under it? That would cause it to have trouble spinning, and maybe the motor was damaged or the axle bent?
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Old 15 January 2014, 13:05   #3
Firestone
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Hi demolition, thanks for the fast reply...

(EDIT: Resized the pics...)

Below you can see pictures of both sides of the diskdrive:



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Old 15 January 2014, 13:33   #4
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A little update on this one... think I found out what the problem is.

The problem may be that one of the heads dont come close enough to the disk, because by accident I tried to turn the drive upside down and insert a disk with the cover off, the drive starts reading the disks again!

So I tried to apply a little pressure on the "cradle" the disk is in and it reads disks now every time. Now I need to find out how to adjust the heads just a little bit so I won't need to apply pressure all the time....

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Old 15 January 2014, 21:35   #5
ElectroBlaster
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I would suggest a good servicing would help!

Bit of a dust clean.

Some machine oil/grease on the worm gear. Some of the disk cradle (not loads mind!) working it in by injecting and ejecting a disk plenty of times and see if that helps out.

I have done this to a few different branded drives with good results
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Old 16 January 2014, 13:28   #6
roy bates
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Quote:
Originally Posted by Firestone View Post
A little update on this one... think I found out what the problem is.

The problem may be that one of the heads dont come close enough to the disk, because by accident I tried to turn the drive upside down and insert a disk with the cover off, the drive starts reading the disks again!

So I tried to apply a little pressure on the "cradle" the disk is in and it reads disks now every time. Now I need to find out how to adjust the heads just a little bit so I won't need to apply pressure all the time....


it shouldnt matter which way round you have the drive,the heads are spring loaded.
and the springs a quite strong.

its more likely the loading tray on the drive, because the disk has to be all the way in and down on the switch to work properly.
and that also effects the heads as it goes in and down the heads are released.
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Old 20 February 2014, 10:59   #7
Firestone
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Okay... now it works nearly every time I insert a disk, so it's not a big problem.

But another thing I'm curious about...
I can see that there is a flag near the step-motor which probably tells the drive that it has reached track 1 (?). But what happens if you reassemble the disk with this stepping motor in the wrong position? Will it be able to find out for itself how many steps it needs to go to go back to the original position?
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Old 20 February 2014, 11:36   #8
Loedown
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Okay... now it works nearly every time I insert a disk, so it's not a big problem.

But another thing I'm curious about...
I can see that there is a flag near the step-motor which probably tells the drive that it has reached track 1 (?). But what happens if you reassemble the disk with this stepping motor in the wrong position? Will it be able to find out for itself how many steps it needs to go to go back to the original position?
The drive should have a home switch so when you switch it on it homes and then it doesn't matter because it knows that's origin, same thing with a cd laser.
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Old 20 February 2014, 12:59   #9
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Algorithm is always same, seek (move head) to start position then allow to computer to set some track, from time to time floppy can perform this even automatically to recalibrate ( for example to compensate aging of mechnics) - this is purely up to floppy servo controller, some of them are dumb type (fully rely in sensor for position 0 and on computer, some of them are "smart" with some small SoC on board to do some things automatically).
--
Aaa and my two cent or useless advise - check always length of screw used to fix drive - sometimes we swap original screw with longer and this can be nasty or to PCB or to mechanics.
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