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Commodore 1571 problems


Kurisu

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Hello everyone! been forever since I have been on here. Hope you all have been well.

ANYHOO, I recently came into posession of a Commodore 128, a Commodore 1902 monitor, and a Commodore 1571 floppy drive. The monitor and the actual computer are fine, and seem to run perfectly as far as I can test, but the floppy drive has something severely wrong with it.

I am aware of how fragile the drives are, and have read quite a bit on the issue, but nothing is quite matching the experience I am having with my drive: It seems to initialize fine, and behaves fine until you actually send a command to it. Then, it will grind senselessly, followed by the flashing green light of error land. It can be turned off and re-initialized just fine, and any commands to force the hardware to do most head-moving tasks seem to go fine, but any actual read or write commands just fail with this same error.

Here's the funny thing: thinking the controller might be bad, and noticing that the machine came with un-installed JiffyDOS, I decided to do my first IC replacement and remove the original controller, and install the new JiffyDOS chip. Installation went perfectly fine, because after install the 1571 does the EXACT SAME THING AS BEFORE! I actually laughed about it, since i clearly had done the install right, but it in no way was related to the drive problems.

To give an example of the issue at hand, if you hit F3 for a DIRECTORY command, the drive will begin to seek, then, will begin it's flashing green light and the commodore will return to it's "Ready" prompt without displaying any data.

I will record video of this later, as I just woke up and decided to post here (go figure, right?). I hope there is an easy fix for this, but if the drive is fried, oh well. I just have a ton of old floppies from the original ower, including much actually user-generated data that would be interesting to look over.

Thanks. Again, I'll record and share video of the issue later today.

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Could be something as simple as a dirty head. Can you try cleaning the head with isopropyl alcohol?

 

Could also be an alignment issue. If you have a blank disk, or one that you don't mind destroying, try formatting it. If the disk formats and then reads correctly then the drive may have just gone out of alignment in storage.

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Thank you for your reply! I had tried formatting, etc, and the drive would always try to work, then result in the same issue.

I certainly should clean the heads when I get a chance, as that can always help things.

I do however, have an update: I read more in depth on the workings of the drive this morning, since this is the first full day since getting the machine that I have had time to do such, and I DID get it to read a directory.. by pushing the head down a bit with my finger...

The result? While I know it cannot be safe for the hardware in the long run, I have a metal plate, actually left over from the IC insertion kit I bought last night, taped to the head assembly very carefully, and balanced, weighing it down to where it reads both C64 and C128 software. I was able to run various Chess games (the old owner loved chess), some word processing software (turns out the owner was a doctor, who took trips to places like Saudi Arabia, etc) and CP/M... so, things seem to be working fine, but the end problem is simply that this is NOT a safe way to run the drive.

I still intend to take video of the drive, operating correctly and with the "fix" and improperly, without the weight attached, but I think I at least found what the final issue was: heads not contacting. Now to figure out WHY this problem existed in the first place.

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It sounds like a spring or something similar is tired and needs replacing? I never opened up a 1571 so I don't know exactly how the assembly works.

 

Did you visit Ray Carlsen's pages? He is a bit of an authority when it comes to Commodore repairs, mainly because he has documented so much of his work.

http://personalpages.tds.net/~rcarlsen/cbm/1571/

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If the drive is left disengaged for years, the thin metal strip that attaches the top head becomes warped and doesn't align properly with the lower head, which makes it not apply the right pressure in the right place to read the disk.

 

You can try to bend it back, but it's difficult to ever get it just right again.

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Hi guys!

Carlsson, yes, I have checked out his guide in my research, which indeed is where I got the idea to at least play around with the drive head, to see the results!

R.Cade, This drive certainly had been in storage for a while, and while it did have the transport card in the drive, the drive was NOT locked down, meaning, during the move from the estate sale to my friends shop, it certainly could have been damaged.

I carefully studied the drive, and I'm not noticing any bent metal... then again, I can only do so much with this being my only specimine of 1571. It looks nearly identical to the photos on Ray's site.

I do believe the spring is the culprit, since adding weight to the drive head causes good reading results. It would make sense then that the force of the spring is no longer enough.

I still have a piece of metal taped to the drive head, and it's still working. I just need to snag another one, or alternately, I need to just get a SD reader for this machine. That would be the best route, and just use the physical drive sparingly. :3

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I will have to take another look in the drive and try this out.

I did go ahead and order a SD reader for the machine, but of course, I want to be able to run original software disks, and make backups of the data the original owner had, so keeping the drive alive is still a priority.

Need to buy some good needle nose pliers for that spring tension trick.

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  • 3 years later...

Anyone have any further resources for 1571 alignment? I am having mixed success, with great trial and error (and a Free Spirit alignment disk) getting better readings from the alignment program, but I still can't get it to read a disk. I am surprised to see so few useful videos and tutorials (for those who don't know anyone who can show them how to deal with this in person).

 

Useful pages or videos? Useful magazine articles? I've seen Carlson's stuff (and bought a PS from him) but it is not visual and doesn't discuss alignment.

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I've never seen a 1571 drive mech out of alignment unless parts were broken - it just doesn't happen almost ever because of the design.

I would suspect some other problem before an alignment issue.

 

Does the drive properly format disks itself and is then able to read them? If no, it's not an alignment problem.

Edited by R.Cade
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I've never seen a 1571 drive mech out of alignment unless parts were broken - it just doesn't happen almost ever because of the design.

I would suspect some other problem before an alignment issue.

 

Does the drive properly format disks itself and is then able to read them? If no, it's not an alignment problem.

 

Actually adjusted the stepper motor position and the thing is improved. Still, it's possible it's all placebo.

 

What is the best way to format and read a disk? I mean, I could probably figure out the command or use a program to format, but when you say 'read' it, do you mean recognize it and catalog it? Or do I need to write some files? I am just learning about disk drives and C64. Now Apple II on the other hand, I know more about.

 

So is the 1571 supposed to be double sided or double density?

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You can look up how to format a disk. If it successfully completes and you can do a directory and save files, then everything else in the drive may be fine.

 

If you've already changed the alignment, all bets are off... Whether it was or wasn't aligned before doesn't matter.

 

#1 problem with the 1571 is the top head gets misaligned and doesn't apply even pressure to the disk. Also, the wires to the top head get disconnected and then the second side won't work.

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You might want to run this program:

 

10 OPEN 1,8,15:PRINT#1,"N0:MYDISK,ID"

15 INPUT#1,E,E$,T,S

20 PRINT E;E$;T;S

25 CLOSE 1

 

It will first format the disk, then read the error channel. You should get 00, OK, 00, 00 as the format command doesn't return any other status IIRC.

 

Other useful commands you should learn:

 

Initialize the disk (basically center the head): PRINT#1,"I0"

Validate disk content (fix block availibility map etc): PRINT#1,"V0"

 

You can omit the zero in all those commands, but it is there from old habits and PET usage which had those dual drives. Obviously the command channel needs to be OPEN when you issue the commands. Also PRINT# must be written as it is or using P SHIFT-R. If you try to use ?# you will get SYNTAX ERROR.

 

The OPEN command consists of three arguments: logic channel (any channel you like in the range 1-63 or so), device number (usually 8, unless you have several drives) and command channel where 15 is reserved for sending disk commands while 1-14 would be used to write or read sequential files etc.

Edited by carlsson
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If the drive is left disengaged for years, the thin metal strip that attaches the top head becomes warped and doesn't align properly with the lower head, which makes it not apply the right pressure in the right place to read the disk. You can try to bend it back, but it's difficult to ever get it just right again.

This is a common problem with the 1571. The best solution is to replace the ahead assy., if you can find one. I have never been able to bend one back into submission - You might have better luck - but this is the problem.

Here is a link to several manuals that are handy to have;

 

http://www.bombjack.org/commodore/commodore/

Edited by motrucker
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You might want to run this program:

 

10 OPEN 1,8,15:PRINT#1,"N0:MYDISK,ID"

15 INPUT#1,E,E$,T,S

20 PRINT E;E$;T;S

25 CLOSE 1

 

 

The program didn't work for me. I used a utility cart to format the disk and then I saved a program and it worked fine. The one peculiarity is that the drive sometimes doesn't stop running when after it's done with a read. I didn't fully take it apart and clean it (IR sensors?) but I did clean the heads and align it (hopefully). So hopefully it's good. I think it will be good for me to use. It would be nice to do a full read write test.

 

Any program you guys recommend for disk drive full read write testing? I have an SD2IEC so I could put any disk image on that. Which reminds me- can I use that SD2IEC as a second drive? I'll try it.

 

Next question, I could start another thread, but hopefully you guys don't mind answering this. I have some AV cables that seem to work with Atari 8-bit stuff, but don't work right with my C64. One of them will output black and white over the white sound channel from the AV cable. Are the 6 pin DIN AV cables for Commodore and Atari completely different? Need a C64 one since that seems apparent.

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