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1541 red light constantly on, spindle behaving as expected, drive not responding.

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
61
I swapped out UC1, of DRIVE 3 and can now get a directory & speed test works.

Not quite there yet, I can load a directory but no programs. The drive spindle speed is maxing out at 260 (with the adjustment pot fully tweaked). Could be a voltage issue, or a slipping belt.. although the belt feels tight.
 

VintageVic

Experienced Member
Joined
Dec 9, 2019
Messages
303
Location
Finland
Glad you are getting there!

Did you try if drive 3 has different result with the other drive mechanics?
Perhaps you need to put original ROM there to get proper result with spinning speed.

I don't really know how speed dos or jiffy changes the drive, but you should not get
directory either with 260rpm. I suspect the speed is misread or misinterpred somehow, but that's just a guess.
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
61
Yes I tried that just last night, it works fine with another mechanism. It looks like either this motor is failing, or perhaps the belt is too loose...

I'll try swapping a belt over - I tried testing the motor resistance in circuit and it came out at 9ohms, the service manual says it should be 17 - I'll desolder it and test out of circuit after trying another belt if that doesn't improve things.
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
61
So the belt is nor more slack than any of the other drives.

I desoldered the spindle motor wires and tested the resistance out of circuit and it is 8.5ohms - so I guess the motor has a shorted wiring maybe?
 

Ruud

Veteran Member
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Nov 30, 2009
Messages
927
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Heerlen, NL
If it isn't too much work, desolder a good one. Then you can be sure.

Remark: I admire your perseverance!
 

VintageVic

Experienced Member
Joined
Dec 9, 2019
Messages
303
Location
Finland
Okay great, so you have narrowed the issue down to the mechanics.

I think I have had a drive that had too much worn out spindle motor. It was giving
a lot of sounds too (from bearings or somewhere). The motor is indeed one possible
failure point there.
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
61
If it isn't too much work, desolder a good one. Then you can be sure.

Remark: I admire your perseverance!

A good one is only 12ohms - the service manual I have states it should be 17. Even more confused now :D
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
61
Okay great, so you have narrowed the issue down to the mechanics.

I think I have had a drive that had too much worn out spindle motor. It was giving
a lot of sounds too (from bearings or somewhere). The motor is indeed one possible
failure point there.

I'm going to search the motor part number, just in case they are still in production.
 

ClassicHasClass

Veteran Member
Joined
Mar 22, 2013
Messages
1,628
Location
Sunny So Cal
Essentially what you insert is what it will try to soft-align to, so you should try to insert a disk that you know came from a well-aligned drive. (I use a Epyx Vorpal Toolkit disk, for example.) Failing that, a commercially duplicated floppy would be the next best thing.

FDC error 3 indicates a sync mark could not be found. FDC error 9 indicates the sync was found, but the checksum failed. In either case you did the right thing by waiting because these code would indicate the drive was still so misaligned it can't read properly. It may take some time for a really whacked drive to come back into position because basically all Torquemada 1541 is doing is smacking the heads around until something is readable.
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
61
Essentially what you insert is what it will try to soft-align to, so you should try to insert a disk that you know came from a well-aligned drive. (I use a Epyx Vorpal Toolkit disk, for example.) Failing that, a commercially duplicated floppy would be the next best thing.

FDC error 3 indicates a sync mark could not be found. FDC error 9 indicates the sync was found, but the checksum failed. In either case you did the right thing by waiting because these code would indicate the drive was still so misaligned it can't read properly. It may take some time for a really whacked drive to come back into position because basically all Torquemada 1541 is doing is smacking the heads around until something is readable.

Thanks for the explanation. I used a 'user' disk that came with one of the drives - I have some CBM factory created disks which I'll try torquemada against instead.
 

VintageVic

Experienced Member
Joined
Dec 9, 2019
Messages
303
Location
Finland
You could also format one of your less important floppy (that does not have software you want to keep).
If the issue is misalignment, you should be able to read and write to that floppy which you format with the drive itself.
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
61
So....

I have removed the mechanism from DRIVE1 and transplanted it into DRIVE3, for some reason the mechanism reads more disks when hooked up to the newer revision PCB in there - no clue why.

BUT, alignment when I check it against a few factory disks now has every track off by 1. There are conflicting views on how best to approach this (or seems to be), some state to use an oscilloscope to view a differential of 2 pins on UF4, and to rotate the stepper motor until the highest amplitude is indicated, and others say to move the head stop. So what should I do?

DRIVE1 & DRIVE3's mechanism hybrid is simply going to be my spares drive unless I can source a new spindle motor.
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
61
Last update on this, I fixed the alignment issue - I had to elongate the adjustment slots on the stepper motor. I guess the motor is tired or the spindle has rotated in the headstop attachment. All good now, and I've managed to source a replacement spindle motor for the other drive with the bad one.
 

BennehBoy

Experienced Member
Joined
Nov 2, 2021
Messages
61
DRIVE1 & DRIVE3's mechanism hybrid is simply going to be my spares drive unless I can source a new spindle motor.

Further to this, I managed to source a spare spindle motor. I fitted this which fixed the slow motor issue, but although I could load a disk directory (slowly), no larger programs would load successfully.

Given that a directory was working, clearly this was not a logic issue, but rather a signal path one.

Head resistances were fine, so I decided that given I had some spare LM592's I would swap those out.

Long story short, the other drive is also now working.

My drive collection has also grown a bit, I've picked up:

* a Master-41 (Excelerator Plus/OC118 rebadge) - that had 2 issues, a factory bodge wire for the oscillator was loose, and the motor controller (a Hitachi HA13431) had failed - diagnosed because the active low 'drive on' sense line resulted in no spinning motor even though all the motor windings were good.

* a 1571 - which was shipped working and arrived non working - must've had a knock during shipping because 3 of the transformer feet had cracked on the PSU pcb - resoldered and all is good.
 
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