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Thread: Commodore 1541 Disk Drive Issue

  1. #1

    Default Commodore 1541 Disk Drive Issue

    The other day I found myself unpleasantly surprised after firing up my C64 to play a game to with a friend, that there seems to be a problem with the 1541 drive.

    After inserting a working floppy disk into the drive, and typing LOAD "*",8,1 and pressing enter, the drive will spin for about 5 seconds then stop.
    The display will say SEARCHING FOR *... and never update again.

    The both green and red lights on the 1541 will light, and the red light will remain on even after the spinning has stopped. The only way to get out of it is to turn the C64 off and back on, but this behavior will occur with each and every attempt of loading a program through the drive.

    It may also be important to note that if there is no floppy disk inserted into the drive, and the computer prompted to load, the drive will spin and actually return that there is no disk to be found.

    It's likely that this is a hardware issue with either the drive or the computer itself, but of course I have no idea how to diagnose the source of the problem. Has anyone experienced a similar issue? Any and all help will be very much appreciated!

  2. #2

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    Quote Originally Posted by BrinkleCasey View Post
    The other day I found myself unpleasantly surprised after firing up my C64 to play a game to with a friend, that there seems to be a problem with the 1541 drive.

    After inserting a working floppy disk into the drive, and typing LOAD "*",8,1 and pressing enter, the drive will spin for about 5 seconds then stop.
    The display will say SEARCHING FOR *... and never update again.

    The both green and red lights on the 1541 will light, and the red light will remain on even after the spinning has stopped. The only way to get out of it is to turn the C64 off and back on, but this behavior will occur with each and every attempt of loading a program through the drive.

    It may also be important to note that if there is no floppy disk inserted into the drive, and the computer prompted to load, the drive will spin and actually return that there is no disk to be found.

    It's likely that this is a hardware issue with either the drive or the computer itself, but of course I have no idea how to diagnose the source of the problem. Has anyone experienced a similar issue? Any and all help will be very much appreciated!
    If you have only one C64 and only one 1541, you can't easily tell on what side of the serial bus lies the fault.
    To further diagnose this issue you would need at the very least a multimeter. A logic probe or better an oscilloscope would be perfect to troubleshoot the issue.
    You would also need to substitute probably an IC on the faulty side of the C64-1541 pair.

    Frank IZ8DWF

  3. #3

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    Quote Originally Posted by iz8dwf View Post
    If you have only one C64 and only one 1541, you can't easily tell on what side of the serial bus lies the fault.
    To further diagnose this issue you would need at the very least a multimeter. A logic probe or better an oscilloscope would be perfect to troubleshoot the issue.
    You would also need to substitute probably an IC on the faulty side of the C64-1541 pair.

    Frank IZ8DWF
    I have access to my college lab tools so I'll be able to use an oscilloscope and multi meter. Additionally, at home I have a regular multimeter as well.

  4. #4

    Default

    Quote Originally Posted by BrinkleCasey View Post
    I have access to my college lab tools so I'll be able to use an oscilloscope and multi meter. Additionally, at home I have a regular multimeter as well.
    Ok so first of all: what kind of 1541 is it? So we look at the right schematic?
    First of all, disconnect the serial cable from the 1541, power it on and check the voltage between pin2 of the serial DIN connector (which is ground) and pin 3 of the same connector, then pin2 - pin5, then pin2 - pin4, then pin2 - pin6.
    You can use a simple multimeter for that, expecting readings from 0V to 5V, steady.
    Frank

  5. #5

    Default

    Do you have access to a diag cart? I think I has a similar problem and I was able to run a diag and see that a CIA had issues, because one of them didn't keep time. I could be remembering wrong, but I think I swapped them side to side and some else stopped working, maybe my keyboard?

  6. #6

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    Quote Originally Posted by jafir View Post
    Do you have access to a diag cart? I think I has a similar problem and I was able to run a diag and see that a CIA had issues, because one of them didn't keep time. I could be remembering wrong, but I think I swapped them side to side and some else stopped working, maybe my keyboard?
    yes also swapping the CIAs on the C64 could give a clue, if something changes. But not all the C64 have socketed CIAs

    Frank IZ8DWF

  7. #7

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    Quote Originally Posted by iz8dwf View Post
    Ok so first of all: what kind of 1541 is it? So we look at the right schematic?
    First of all, disconnect the serial cable from the 1541, power it on and check the voltage between pin2 of the serial DIN connector (which is ground) and pin 3 of the same connector, then pin2 - pin5, then pin2 - pin4, then pin2 - pin6.
    You can use a simple multimeter for that, expecting readings from 0V to 5V, steady.
    Frank
    I was unaware that there are multiple types of 1541 drives. All I know is that this is strictly a 1541, i don't know if there's any extra letters or numbers that go along with it for the model number. In an attempt to clear up confusion, attached is a picture of the exact model of disk drive I'm talking about. 300px-Commodore-64-1541-Floppy-Drive-01.jpg




    Voltages

    Pins Voltage
    ----- ----------
    2-3 0 V
    2-5 0 V
    2-4 6.63 V
    2-6 0 V

  8. #8

    Default

    Quote Originally Posted by BrinkleCasey View Post
    I was unaware that there are multiple types of 1541 drives. All I know is that this is strictly a 1541, i don't know if there's any extra letters or numbers that go along with it for the model number. In an attempt to clear up confusion, attached is a picture of the exact model of disk drive I'm talking about. 300px-Commodore-64-1541-Floppy-Drive-01.jpg




    Voltages

    Pins Voltage
    ----- ----------
    2-3 0 V
    2-5 0 V
    2-4 6.63 V
    2-6 0 V
    hmm 6.63V isn't really a good sign unless your multimeter is out of calibration by a large margin. Are these voltage taken with no cables attached to the 1541? All those 0V mean faults.
    It's something I've never seen on a faulty 1541.
    First check your multimeter's calibration on the C64 user port. Measure between pins 1 and 2 of the user port where there should be 5V (4.9 to 5.2 I'd expect).
    https://www.c64-wiki.com/wiki/User_Port

    Frank

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