1541 Drive - Drive Re-alignment

The saga of the 1541s continues.....

Episode 2: The Phantom Loading
OK, so I have one of the 1541s that at least initialises on power-up, with no flashing LEDs - that's a fair start. It's also as far as I've got, as the drive won't load anything, it just sits there flashing the red LED.

A quick Google tells me that the head may be out of alignment and that the tolerance on the tracks is 1/32" (about 0.8mm in new money). Not much room for error there, then. Fixing it involves loosening off the stepper motor screws and tweaking the stepper motor back into it's original position - this sounds iffy and full of ways to screw things up. There are various discussions about adjusting drive stops and this also fills me with dread. With so many adjustments, how are you to know which one is out of tolerance?

Other documents tell me to check the drive speed, using the patterns underneath the drive assembly using a fluorescent light as a strobe - that's easy enough. Cleaning the head with Isopropanol is easy-peasy too.

Fault finding guides are scant at best and contradict each other with trolling comments at worst; I'm not sure whose guide is the most reliable.

I don't have an oscilloscope to hand and I'm beginning to think that I may need one to get a 100% result with this drive.

What I really want to know, before I scrub up for open-drive surgery, is this; has anyone on here carried out this operation on a 1541 and did the patient make a full recovery....??

:help:

Hey Merlin,

Drive alignment issues have always been prevalent in the 1541 drives. Unfortunately, the only way I know how to align these drives without an oscilloscope is using alignment software that has a specially formatted disk to allow you to align the drive.

The one I have is from Free Spirit Software. You basically load the program, flip the disk then start aligning the drive. You keep the stepper motor screw loose and manually move the head until you have it aligned then you tighten the screw back down.

You see new old stock come up on the other bay quite a bit. Just be 100% certain it's an original because there is no way to copy the specially formatted tracks on the back of the disk. :)

http://www.commodore.se/bilder_128/1541drivealig.jpg

Good luck!

Heather

Hi Merlin,

There are several things that could cause this problem other than a misaligned drive.

The simplest cause is dirt build-up. Try giving the drive head and rails a clean.

If it still fails, reading the disk error channel with this proggy will help track down the problem:

Code:

---

10 open 15,8,15
20 input#15,a$,b$,c$,d$
30 print a$,b$,c$,d$
40 close 15
run

---

It's probably worth trying a few different disks too. It may be the media that's goosed!

Ray Carlsen has one of the best fault-finding guides for these drives.

Thanks to you both for the advice.

I think I'll be carrying out a thorough clean and examination of the mechanicals before I go adjusting anything. Ray Carlsen's guide has given me food for thought about side effects of dirt in these drives and to be honest, they could be a lot cleaner inside.

One of these drives has the remains of a toggle switch on the front that isn't original. I presume that this switch was to select drive 8 or 9, however I'll take a picture of where the wires connect on the circuit board to see if that throws up any clues as to what the switch does. The switch is broken and will need to be replaced anyway.

I'ver also obtained some nice shiny new M3 screws, to secure the case lids; one of the drives only had three screws and the other had none at all.

I get the feeling that these drives are going to be a repair and a restoration, all in one....

Hi Merlin

Do the drives have the same mechanism?
Afair there were only two types of mechanisms in the old 1541 (non mkII) drives.

First thing I'd try, is swapping the boards between them, to verify your problem is not electronic.
I've seen electronic faults which cause the behavior you're describing.

@ Uberfreak

No, the two drives have different issues. I am working with the one that appears to have the best chance of survival at the moment. Once I have a known working unit, it may help me trouble shoot the other one, as they are both the same type of 1541 drive (the later version with the vertical latch that was made before the 1541-II and 1571 came out).

The second drive powers up but the red LED keeps blinking three times, which is hinting at a corrupt ROM or something wrong in the power area feeding the ROM.

I would rather try to get one working unit without cannibalising both of them, as I know that TC would like the second unit.

I'll keep posting in here as progress is made.

I found this interesting post by Eslapion on a Commodore forum last night...

Making your own amplitude signal display device...

After sifting through my old junk I found one of the VU-METER kits I made for myself years ago but never used. This is a kit made by Velleman and it still sells. The product code is K4304 see:

http://www.vellemanusa.com/us/enu/product/view/?id=350543

It is sold at jameco for 16.99$ It is designed to be powered with 10-15Vdc but I STRONGLY suggest you do NOT use anything other than a battery to power this thing to make sure its ground level remains floating if you are ever to attach it to a 1541. Most importantly DO NOT use the 1541's own internal 12V regulator at a source as it will cause a short circuit if you attach the ground input line of the kit to one of the outputs of the LM592.

This thing uses an LM3916 (which can easily be replaced with an LM3915 or LM3914, as you see fit) and an ultra low cost LM741 op-amp.

This obviously converts AC into DC to display the signal's amplitude as it was designed for audio... The cheap LM741 acts as a low pass filter preventing the device from being sensitive to higher than audible frequency signals.

I replaced the LM741 which is basically a 25 cents op-amp with a TL081 which is a 39 cents op-amp (biiig deal), it is a much faster pin compatible replacement and the frequency range jumped tenfold to around 100kHz.

In other words, with this kit and a 39 cents chip, you should be able to do it the way I do it. Of course, an oscilloscope is always better to find the exact point at which you will get the very peak amplitude but I guess the difference will be mostly insignificant.

Enjoy!

I think that Maplin still stock Velleman kits in the UK; if so, this could be the answer to my head alignment issue..... :)

Still, swapping the boards will give you a clear idea of the problem.
It could be electrical & not dirt or alignment related, will save you time :)

Merlin,

Clean it, oil it etc.. Never had alingment issues..

Oo maybe you got jiffydos installed? (switch?) In my youth we used to "lend" each other drives, etc mine was alway's id 9.

If you are going to use the system a lot you should have two drives, that allows you to copy disks in 20 secs. (without the computer running)

Have fun:thumbsup:

For a modern day C64/C128 setup, I would actually say it is good to have a single 1541 drive and an SD device, such as the uIEC. This allows you to easily copy disk images from your modern day computer to real floppy disks using the C64 itself. :) In my past experience, dual 1541 drives were only useful for copying floppies and using GEOS because most games/applications would not take advantage of the second drive.

Keep us updated Merlin!

Heather