1541 Newtronics can't format but reads most disks

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foobrew
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1541 Newtronics can't format but reads most disks

Post by foobrew »

I have a 1541 Newtronics model exhibiting the following behavior:

Cannot format a disk
Attempting to format a disk, it produces the following error right from the start (~2 sec after issuing the command and hearing the head move):

Code: Select all

21 READ ERROR 00 00
The Performance Test fails with inconsistent errors each run
Running the Performance Test from the Commodore 1541 disk and also the World of Jani suite produces the following errors. These errors represent multiple runs of the program and, as you can see, the errors are always similar but not always the same:

Code: Select all

WRITE TRACK 1
                       21 READ ERROR 1   0
UNIT IS FAILING

READ TRACK 1
                       21 READ ERROR 1   0
UNIT IS FAILING
Another run:

Code: Select all

21 READ ERROR 20 6

21 READ ERROR 1 0
Another run:

Code: Select all

21 READ ERROR 0 0

20 READ ERROR 17 0
And yet another run:

Code: Select all

21 READ ERROR 0 0

CLOSE FILE
71 DIR ERROR 18 1
Cannot write to disk
Attempting to write a small, 2-line BASIC program to a disk formatted on a different C64 produces the following error:

Code: Select all

25 WRITE ERROR 16 01
What's interesting here is that something is written to the disk since the dir shows a new file but attempting to read it fails, of course.

It's able to read most disks
  • User-formatted disks containing various progs can be read without any issues.
  • Curse of the Azure Bonds (commercial disk) can be read without issue every time.
  • Pool of Radiance (commercial disk) fails to read 9/10 times. I actually have two commercial copies of this game and both exhibit the exact same behavior. I think the success/failure rate may be related to the built-in fast-load feature for this game but I haven't done enough testing with it enabled/disabled to be sure.
Basic testing of the drive head is good.
I cleaned the head and also tested and confirmed continuity across all pins of the head.

I've looked at Ray Carlsen's fix1541.txt document and also SAM's Commodore 1541 Troubleshooting and Repair Guide but I'm still stumped as to what the problem could be. It reads most of the time, but not all, and it's never able to write anything. Yet, the continuity on the head is good...but I'm not sure that completely rules out head issues. Any suggestions?


banman
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Re: 1541 Newtronics can't format but reads most disks

Post by banman »

Hi foobrew,


Not really sure what the issue is on your disk drive. It can be very frustrating to troubleshoot these things.

Check out this thread...


viewtopic.php?t=14055


It might be a way to rule out your VIA chips.

This thread has some great advice on properly cleaning the disk drive read/write heads.....


viewtopic.php?t=15713


I hope that this will help you.
rmzalbar
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Re: 1541 Newtronics can't format but reads most disks

Post by rmzalbar »

Is this a 1541C model (white case, "shorter" board.) Is the felt pressure pad present and in good condition. Is the spring providing good pressure - If you try your format test again, but rest a finger on the top of the head load arm to provide a little extra pressure, does it improve.
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foobrew
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Re: 1541 Newtronics can't format but reads most disks

Post by foobrew »

Just an update for a few things I tried.

Swapped the 6522 chips in UC2 and UC3 with no difference in behavior. Also hit the sockets with some Deoxit.

Checked resistance across each of the head pins:

pins = ohms
1-2 = 11.7
1-3 = 25.1
1-5 = 23.3
2-3 = 13.7
2-5 = 11.9
3-5 = 25.1

As you can see, all values were quite low and within the same general range.

I'm thinking to try running it without the cover on next to see if I observe any disk slippage. Not sure if the symptoms would match what I'm seeing but it's an easy enough test.

If the mechanical aspects are all within bounds then it's time to look closer at the electronics. What should I look for? Could bad capacitors cause this kind of behavior? I've visually examined all of them and don't see any leakage.
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Zippy Zapp
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Re: 1541 Newtronics can't format but reads most disks

Post by Zippy Zapp »

Hello. You mentioned that you cleaned the heads but did you check the drive rails? If they are sticky and or dirty it can interfere and for sure cause read errors. You could clean them off with cotton swabs and Isopropyl alcohol and then use a tiny bit of 3-in-1 silicon oil to lube them or whatever you might have. With the drive off they should move freely.

Other then that it could be an alignment issue but usually a misaligned drive will still format a disk. In the past I have found that the little grove in the heads can sometimes get debris in it that a simple head cleaning will not dissolve. In those cases I use a cleaning disk which does a good job at scouring the thing. Also windex/glass cleaner can sometimes work better, followed by Alcohol to remove the windex.
Commodore - Changing the world 8 bits at a time.
banman
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Re: 1541 Newtronics can't format but reads most disks

Post by banman »

Hi Zippy Zapp,


I too have experienced this issue of debris clogging up the little grove on the disk drive read/write head.

I have always been worried about going in too hard on cleaning the head owing to the the advanced age ànd lack of replacements for these parts.

Your suggestion of using the cleaning floppy disk is a great idea! :D

Do they still sell these cleaning disks?
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Zippy Zapp
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Re: 1541 Newtronics can't format but reads most disks

Post by Zippy Zapp »

You can still find NOS cleaning disks. I still have a couple from back in the day and they still work good. You can use IPA as the fluid since the "head cleaning" solution that they included was probably the same.
Commodore - Changing the world 8 bits at a time.
banman
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Re: 1541 Newtronics can't format but reads most disks

Post by banman »

Hi Zippy Zapp,

Thank you for this information. I will have a look around on eBay. :D
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