Replacing the head on a 1541 disk drive

I have a bunch of these 1541 drives for the C64 and C128, two of them weren’t working. Every time I tried LOAD "$", 8 it gave me a FILE NOT FOUND error.
At first I thought it was a dirty head, but in fact the head was busted, I had to replace it.

I’ll show you how to replace it, but you’ll need another working disk drive to align it.
Tools needed:

  • Screwdrivers.
  • A working 1541 or 1571 disk drive.
  • New Head replacement.

Let’s start by removing the top case, the drive has four screws in the bottom.IMG_2973

Now with the case open, we need to remove the metal shield.IMG_2976

The main board is exposed, remove the screws.IMG_2980

Detach all conectors.IMG_2981

One easy way to tell if the read/writing head is broken is testing this black connector with a multimeter. It should have continuity between all the pins. Let’s say you try pin 1 and 5, they should have continuity, pin 2 and 3, continuity, pin 2 and 5, etc.. If one of these combinations don’t have continuity the head is broken.IMG_2983

Set aside the metal pin that connects the lever with the disk drive mechanism.IMG_2986

Now remove the 2 top screws that retain the head.IMG_2988

Cut the zip tie that holds the wires in place. IMG_2989

Keep removing parts as in the photos.IMG_2990

These 2 pieces of metal holds the rails in place.IMG_2991

We need to remove this spring, be careful not to lose it.IMG_2993

Now remove the screw that holds the metal strip in place.IMG_2994

Head removed!IMG_2995

Now we need to remove the metal chassis from the plastic case.IMG_2996

I removed the drive from the chassis for a cleaning, but you don’t have to, you can assemble the head and align the drive with the drive in the chassis.IMG_2998

Drive and chassis with power supply separated.IMG_2999

IMG_3001

The new working R/W head. To install it, follow these pictures.IMG_3003

IMG_3004 IMG_3006 IMG_3008 IMG_3010

Tighten the screw and lock it with nail enamel.IMG_3012

Add one drop of oil to each rail.IMG_3014 IMG_3015 IMG_3016 IMG_3017

Put a new zip tie to hold the wires in place. Remember to leave enough room for the head cable to move.IMG_3019 IMG_3020

I’ve removed the stickers because I’m gonna retrobright this thing. Check the difference in color.IMG_3023 IMG_3029

Don’t forget to plug all the connectors to the main board.IMG_3030

Ok, now comes the drive alignment part. Loosen these 2 bottom screws that holds the motor in place. We just need to loosen them enough so the motor can move with our hands.

IMG_3032

This is why we need a working second floppy drive, because we need to load the alignment program. I’ve used here the “Free Spirit Alignment software”.

IMG_3033

Notice how I’ve placed the drive on it’s side. This is for a better access to the motor that we need to align. Also be careful as the power supply contains high voltages. IMG_3035

Load the program and follow the on screen steps. It’s important that you know the disk you’re gonna use to align the drive is aligned itself. I’ve used an original Commodore 1541 Test Disk.IMG_3037 IMG_3038 IMG_3039

When you hit this screen start to move the motor with your hand, in one direction and then the other until you can read “ALIGN. CONDITION: Excellent” or SATISFACTORY. IMG_3040

Moving the head back and forth until alignment is met.IMG_3041

After the alignment is done, lock the screws in place with nail enamel. It’s important not to move the motor when you tight the screws.IMG_3042

That’s all! Now we have an aligned 1541 floppy drive. Some guys will say that you need a special disk that was recorded in a certain way to be able to align the drive, some other will say that you need an oscilloscope to do it, Although these things are true, you can align the drive by hand with a known good floppy disk. I did it and I’ve recorded disk using the drive and then tested them on another 1571 drive successfully.

If you have any doubts, comments, feel free to ask.

 

Dario

 

6 thoughts on “Replacing the head on a 1541 disk drive

  1. Hi, Dario,
    My name is Mark. I’ve been troubleshooting a 1541 drive (with the Newtronics mechanics). I think the R/W head is bad. I got the same error you did, “File Not found.”
    I did the multimeter check on the R/W black connector . Yes, not all the pins had continuity. However, I have a working 1541(same model), and I checked its pins too. They don’t all have continuity between them either. Did I miss something? I did it with the power removed. Any ideas?
    I’m off to shop for a new R/W. I’ll be using your website a guide. Thanks for posting it.

    PS. Here’s all the t/shooting steps I’ve taken to get to this point:
    1- Of course, cleaned the R/W head.
    2- I swapped the logic boards between the two drives. The faulty drive still wouldn’t read a disk. That’s when I suspected hardware.
    3- I just received an alignment disk today. The faulty drive did responsed to the alignment, but it wouldn’t register any speed output during the speed test. I’m really thinking the head is dead.
    Well, that’s in a nutshell. Thanks again for your website.

    1. Hi Mark,
      R/W head failure is more common in Newtronics 1541 than Alps mechanism.
      Are you sure about the measurement you did on the working drive? It should give you continuity on all the pins. Detach head cable and measure again, you need to measure the cable itself, not the pins on the board.
      If you already swapped boards with the working drive ad the problem persist, I bet the culprit is the R/W head.

      Did you try to format a disk? A misaligned drive should be able to at least format a disk.

  2. Hi Dario,
    Is there a specific resistance that should be read between any of the wires? I read 0 ohms for all except pin 5 (erase head) on that one I was reading 15 kohm which seems to correspond to a 15 kohm resistor on the bottom of the head.

    Thank you,
    Matt C.

    1. Hi Matt, I don’t remember the resistance values, It’s been some years since I fixed these drives. Do you have a continuity tester with a speaker? It should beep if the continuity is enough.

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