Getting one working Floppy Drive from two non-working ones
 

Hello,

Had two non-working JU-253-033P Floppy Drives. One of them had the back motor not working and the other one had the bottom motor not working. I decided to get one working floppy drive by moving the back motor (including head) from the drive with the bottom motor broken to the one with the bottom motor working.

My only concern is a small ball. I first saw it on the head at the part which joins with the back motor. I attached a photo of this. I would think they would not have placed it there for nothing. I do not understand where this goes exactly. Without it the header still move however.

Does anyone know where this small ball would go and if it is essential or not?

The complete drive looks to be working (without the ball), head moves, bottom motor works, detects disk, etc, but does not recognize any disk inserted (DF0:????). When I use SysTest, [F5] detects 80 cylinders in the inserted disk, [F6] says READY in good time (3.469ms) but says Cannot Read Track 0.

Would anyone know if the above is related with header require calibration?

I have been reading about floppy disk alignment and found the following;

"De-calibrated drives show the following symptoms: They read disks written by themselves fine, but fail to read other disks reliable, and disks written to by the decalibrated drive do no longer work reliable in other disk drives. In case the drive just doesn't work at all anymore, something more is broken."

I therefore got a good floppy disk and formatted with this drive. It did format the disk and it recognise it. However after switched off the amiga and tried the same floppy disk again it did not recongise it again. I tried to format it again and it tells me "cannot format cylinder 0".

So first signs was that it was a calibration issue. However not sure after what happened after.

hmm .. When I select [F6] now it tells me "No Ready Signal". I cconfirmed correct setting is on the back of the drive which I did not change from before. What else can determine READY signal being issued correctly. I have only changed the sector zero and header positions. Did not touch anything else on the board.

Found on another thread that "Ready is true when the disk is inserted and the disk has achieved the correct RPM". Now the message I have is "No Ready Signal" no that Ready is false (don't know if the same, but a floppy drive with no floppy disk in it also gives "No Ready Signal"). So, I know that floppy inserted detection is working as when I insert a floppy disk I get icon on Workbench. So the RPM would be the problem. Wonder if a low RPM would give trouble to read data from the disk.

The ball bearing is where the end/tip of the track motor worm gear rotates/spins on the whatchamacallit (sorry, don't know what to call it).

The missing ball bearing will affect the track motor movements so it could be affecting reading and write.

And if you have been messing with the track motor and read/write heads then it certainly needs re-alignment.

As you have found, the ready signal is normally triggered (it is actually active low - meaning it is low when it is 'true') when certain conditions are met:

* When a disk is present
* When the motor is spinning fast enough.

The 'motor spinning fast enough' is based in the pulse signals. You should be seeing the pulse signals value increment in Amiga Test Kit floppy disk signal tests - normally when you start the motor signal, you should see the pulse signal value increment for every full rotation of the floppy disk.

Ok, I have done some tests with a healthy floppy drive and then again on the one I am trying to get working.

From Amiga Test Kit, when I do a signal test [F5] and use the motor on/off option [F5] on the healthy floppy drive I can see the Index Pulses increase and time values in ms being provided. When I do the same on the floppy drive I am trying to fix I can see the bottom motor spinning but the index pulses remains 0 (exact line says: "Index Pulses (period 0us); MTROn->RDY1 0us")

Could this be a capacitor issue? i.e. - bottom motor spinning so slowing that it is not even getting detected?

Edit 1: If I had to say, visually the bottom motor of the healthy drive looks to be spinning much quicker than that of the drive I am trying to fix.

Each pulse should be when a magnet on the fly wheel goes over the hall effect sensor chip. If it is not getting a pulse for whatever reason then you will not get a ready signal, which will mean it won't do anything.

So when I use Amiga Test Kit and trigger the bottom motor I can see it spinning. Possibly slower that that of another healthy drive I have but it does spin.

What I am sure of is that the drive stopped working after I did a format when checking if the issue was with the head alignment. The format completed successfully but after that the drive stopped recognizing anything even the disk I just formatted and started not reporting the ready signal.

This reminds me of a JU-253-033P Floppy Drive which used to do me the same thing. Would work for a couple of minutes but if I format a disk it would stop detecting any disk for a couple of days. I never fixed that one as since it was partially working I decided to leave it as is.

Could this JU-253-033P Floppy Drive (different from the one just mentioned) be suffering from the same thing? i.e. - some model issue?

Based on the above, if the problem is with the "hall effect sensor chip" could the cap at the floppy disk entry be the culprit? Is there a way how I can test this capacitor?

Can confirm the above. This morning I plugged in the floppy drive again. I did a signal test from Amiga Test Kit and it started giving a Index Pulses. When doing a read test it now says READY too fast. I then tried to format the disk and this worked.

So it would look I have two problems;

[1] Header alignment (this is obvious as I transplanted the whole header part from abother drive).
[2] Bottom motor intermittent issue.

With regards to [2] - given it did not work at all for all yesterday, and this morning after leaving the drive for a night it started giving different behavior - does this mean the issue is that capacitor at the floppy drive opening?

Had an extra 10uf capacitor and replaced the front capacitor of the floppy drive, the one next to the floppy drive opening. Unfortuanstly got same results. Drive ready signal works for some time but then stops. So the capacitor does not seem to be the problem.

You mentioned in your first post that it cannot find track 0. Is this still the case?

When it is working (has READY signal) I can format a disk with the drive and calibration with Amiga Test Kit says it is working. After I use the drive for a couple of tries at most it stops working again (READY signal is lost).

Just to give another example; After I recapped I did a signal test and it worked fine. But after I did a signal test for maybe twice more it simply stopped increasing the index pulses.

EDIT: Sorry forgot to say, when I used a disk formatted with same disk drive (as before) the READ Test worked fine the first time, but as explained after a couple of uses it again says it cannot get a READY signal.

I have checked the voltage on the new capacitor and it is a solid 12.5v when turned on. So don't think that is the problem.

Given the READY signal is issued when;

[a] When a disk is present
[b] When the motor is spinning fast enough.

and given the floppy drive does recognize a disk when inserted, then the only problem must be either (i) the bottom motor not spinning fast enough or (ii) not being detected to be spinning. The fact that index pulses remains 0 makes me think it is (ii).

This is where my analysis is so far ...

Is track 0 detected?

If ATK is not seeing the index pulse signals then this is a likely issue, or related.

I have one of these drives where the pulse signal is not working. I tried replacing the hall effect sensor chip but that didn't resolve it (it is possible I didn't get the right hall-effect sensor chip).

It seems this a common issue with this make/model of drives - the index pulse signal stops working.

When I used a disk formatted with this drive (while I had the READY signal) yes. But the moment I loose the READY signal nothing else works.

Will try replacing the "hall effect sensor chip" from the dead drive. It could well be the other drive sensor is also dead so don't know how much success this will bring.

The TRACK0 signal should work independently of the the READY signal.

In ATK floppy drive signal test, if you press "F6: STEP" this should alternately step in and out of track 0 every time you press it.

When I first enter in the Signal Test screen [F5] I can see the head move full forward and then backwards. The screen says:

If I press F6 (Step) I can see the head move one click forward. The screen then says:

If I press F6 again head moves one click backwards and gives same reading as mentioned previously (TK0).

I guess this means Track 0 is being read. Is this correct?
If yes what does this say? Confirms that "just" the RPM detection is not working?

Yes, that indicates track 0 is being detected and the signal is working.

So it does look like the only issue is the index pulse is not working.

This make/model of drive seem to be prone to this issue. I've still not yet figured out how to fix mine.

Well I'll keep updating this thread if I find anything. Btw - is the hall effect sensor the one highlighted in red in the attached picture?

(Please ignore the missing capacitor further down. I took that photo after I removed it. There is a capacitor there when doing the tests)