Commodore 1541 Drive Problems

[antiquekid3]

So I finally got a Commodore 64 with a bunch of 5.25" disks and the 1541 disk drive. Unfortunately, the drive seems to be broken. When I plug it in and turn it on, neither of the LEDs light up, but the motor does hum and spin.

Where should I go from here?

Kyle

 

[Raven]

Ordinarily both LEDs turn on. The one on the casing (green) denotes that the drive is getting power. The one on the drive (red, usually) means that the disk is being accessed, but just stays solid red until the C64 gives it some kind of signal, at which point it turns off.

Try powering the drive on without the C64 turned on, and see if the light on the drive itself stays on.

If so, it could just be a bad LED for the power light.

Do you know enough to test the drive? If not I can walk you through it.

 

[antiquekid3]

Well, it sure is getting power! That motor is definitely spinning in there. Neither LEDs turn on no matter what...

Should I take it apart and check it out? Probably needs a good dusting...it's been in storage for many years.

I have the manual for it, but when I connect the drive to the C64 like the manual says, the C64 says it can't find a drive connected.

Kyle

 

[antiquekid3]

DRIVE DEAD... OR NEARLY

Lets take it from the top. Does the drive start up properly when turned
on? If the power light (green LED) doesn't come on, or is dim or flickers, you
probably have a power supply problem... the 5 volt line is bad. That usually
results in a spindle motor that runs continuously with red LED off. Check the
bridge rectifier (CR3 in early version drives with PCB# 1540050, and CR1 in
later version drives with PCB# 251830) and the 5 volt regulator VR2. Note: if
the regulated 12 volt supply fails, the motors will not run at all. That's a
rare failure.

http://personalpages.tds.net/~rcarlsen/cbm/fix1541.txt

Well, this website I found seems to indicate the 5V supply is bad. I suppose I'll take it apart and get my Simpson 260 after it!

Kyle

 

[Raven]

That sounds like a pretty accurate description of the problem - have at it! :O

 

[antiquekid3]

Alright, so I'm in Virginia right now without my C64, but I do have an update on the drive.

Turns out the power supply was okay. The Molex connector connecting the power transformer to the board was NOT okay. One of the blue wires (which eventually is rectified/filtered into 5VDC) was not making a good connection with the board. After a cheap fix, it's now working.

Or is it? Yeah, it lights up and all. It seems to do what it's supposed to do. So I hook it up to the C64 and load a disk. It works! It prints the contents of the disk after loading "$",8. I don't know a lot about C64s, but I presume it's safe to eject the disk after powering down the C64 after I see it loads. Just for fun, I go get another disk and try it out. It doesn't load it. You can hear the motor kick on and the red LED flickers a bit, but then the motor stops and the red LED goes completely off. The C64 is still trying to load the disk.

Also, sometimes the red LED will go on and off, maybe about 2 or 3Hz. What could this mean?

So what is going on? I already cleaned the head. Is this a sign of the head needing realignment? Gosh, I hope not.

BTW: This is the "less common" kind (so I've heard) that doesn't have the lever, but rather the thing in the center you push down on.

Kyle

 

[antiquekid3]

Any ideas, anyone? I'll be back home tomorrow when I can try more things, but I'd definitely like to know what I need to try/do to get it working again.

Kyle

 

[SUCCESS]

The drive had read a directory, so it isn't missaligned at all.
Sometimes, due to some disk errors, the drive get lost. Ok, it sounds a bit crazy ...
The drive park at track 18 when finishes its work. Track 18 is the central track which hold the directory
If the drive didnt park at track 18, because it hanged, even powering off and on will not solve the problem. The head remain over a track different form the directory track and will fail to read the directory data.
You can:

1) format a disk. This will force the drive to bump the head and initialize its position.
2) initilize the drive. This is acomplished with 3 BASIC instructions

OPEN15,8,15
PRINT#15,"I"
CLOSE 15

3) Usign an alligment program you can initialize the drive and also check the alligment in all tracks
http://home.comcast.net/~safeharborbay/tcr/cbm/1541.html

Check the software at the end. To transfer it to the 1541 you will need the famous X1541 cable ....
Its a good tool, because you can connect the drive to the PC, transfer files and format disks through a DOS soft called star comander (a sort of Norton Comander). The cable is a MOST in order to put in the 64 all the games and soft avaiable on the web.

Finally, try several disks. Old disks are 20 years old or more. They are likely to cause read errors and force the drive to bump the head. If the drive does it several times, it can go missaligned.

The alligment process is very hard and complicated. I tried this in one drive without any success. I worked for hours on it. Eventully I got it working but it stoped working later and never come back again =(.

 

[geoffm3]

The drive had read a directory, so it isn't missaligned at all.
Sometimes, due to some disk errors, the drive get lost. Ok, it sounds a bit crazy ...
The drive park at track 18 when finishes its work. Track 18 is the central track which hold the directory
If the drive didnt park at track 18, because it hanged, even powering off and on will not solve the problem. The head remain over a track different form the directory track and will fail to read the directory data.
You can:

1) format a disk. This will force the drive to bump the head and initialize its position.
2) initilize the drive. This is acomplished with 3 BASIC instructions

OPEN15,8,15
PRINT#15,"I"
CLOSE 15

3) Usign an alligment program you can initialize the drive and also check the alligment in all tracks
http://home.comcast.net/~safeharborbay/tcr/cbm/1541.html

Check the software at the end. To transfer it to the 1541 you will need the famous X1541 cable ....
Its a good tool, because you can connect the drive to the PC, transfer files and format disks through a DOS soft called star comander (a sort of Norton Comander). The cable is a MOST in order to put in the 64 all the games and soft avaiable on the web.

Finally, try several disks. Old disks are 20 years old or more. They are likely to cause read errors and force the drive to bump the head. If the drive does it several times, it can go missaligned.

The alligment process is very hard and complicated. I tried this in one drive without any success. I worked for hours on it. Eventully I got it working but it stoped working later and never come back again =(.

Excellent link! Also good info on the X1541 cable... a must have if you're trying to get disk images onto a disk to use with a real C-64.

Unlike you I had a little better experience with aligning disks. I've done three or four 1541s, and I did a 1571 after replacing an upper torn head on the drive (donor head from another PC mech, a little glue here and there...)

 

[SUCCESS]

Yea ... a bit annoying.

I've Just read the article yoo linked unsing an scope. Since I had one, I put it on UF4. There's no 70Khz at all. Just a 1Mhz noise at 100mVpp. Sounds like noise picked from the logic circutry which is running near this frec.
The electronic circuit board works fine. It was put in an alligned 1541mecha and reads perferct.
Judging by the progress I achieved at the begining (I get the drive working, even I could load a game) ... I guess I'm not wrong in the procedure. But then ... something just happaned (broken).
IMHO, there's no signal coming from the head anymore. The signal coming from the amplifier IS THE SAME with or without disk !!!!!!. It has no sense. I figure that I cannot allign the drive because I had another problem there .....
Anyway, I will try the soft using the joystick which makes half tracks.
The program I had been using ("1541ali" taken from the web I linked) only do full tracks. Instead of swaping board in order to load the soft with an alligment mecha, I use a working 1541 to save this program to tape usign a C64 file transfer utility.
Then, just load the soft from tape. Only 12 tape turns !!!. I loads pretty fast and it's safe since you need to cope with bard connectors while all the things are powered ... like you said, static here, shorts there ...

A bit slow .. but datasettes runs forever and pretty easy to fix.

Excellent link! Also good info on the X1541 cable... a must have if you're trying to get disk images onto a disk to use with a real C-64.

Unlike you I had a little better experience with aligning disks. I've done three or four 1541s, and I did a 1571 after replacing an upper torn head on the drive (donor head from another PC mech, a little glue here and there...)

 

[geoffm3]

Interesting... with the good mech, do you get the 70kHz signal from the amp?

 

[SUCCESS]

Now I'm a bit scared to swap the boards ... because the donor drive is working and I don't wan't to disturb it.
If I had known about this measurement tip when the boards were swaped, I would have done it
Let me see ...

Could you tell me something ? ... How can I measure the head ... that's: Is there some way to measure the head in order to see whetever if it works or not ?.

Measuring betwen pin 1 and 5 (the RW pins) it reads 15K, but theres a sort of terminator resistor (15K) in the head, so that's what I get ... Is it rigth. What about the other wires ? .. the white and yellow ones ?.

Thnks

Pedro

Interesting... with the good mech, do you get the 70kHz signal from the amp?

 

[geoffm3]

Now I'm a bit scared to swap the boards ... because the donor drive is working and I don't wan't to disturb it.
If I had known about this measurement tip when the boards were swaped, I would have done it
Let me see ...

Could you tell me something ? ... How can I measure the head ... that's: Is there some way to measure the head in order to see whetever if it works or not ?.

Measuring betwen pin 1 and 5 (the RW pins) it reads 15K, but theres a sort of terminator resistor (15K) in the head, so that's what I get ... Is it rigth. What about the other wires ? .. the white and yellow ones ?.

Thnks

Pedro

According to the schematic, Pin 3 is the Erase head, and Pin 4 is common. What continuity do you read between pin 1 and pin 4, and then pin 5 and pin 4?

I would expect with the head disconnected from the board, you should see some activity while on track with the drive motor spinning on your oscilloscope. I haven't had a chance to try that though.

This site has the commodore service manual and schematics...

http://www.zimmers.net/anonftp/pub/cbm/schematics/drives/new/1541/tech/index.html

 

[SUCCESS]

Let's update ....

Today I decided to swap the boards again. I put the board from the drive I can't allign anymore in a drive which is fully working.
The board worked fine. Also, I measured UF4 and got a nice signal I didn't measure the frec and Vpp. The key fact is that the signal is TOTALLY different from the one taken with the bad drive using the same electronics.

Also, I measured the head resistance (DC) of the good one. It read only 30 OHMS betwen 1 and 5 and the half betwen 1 or 5 to common. Looks like two coils with center-tapped to common

Then, I mesaured the bad mecha head and the resistance from 1 to 5 was 15K, From 1 to common only 15 ohms (OK), but From 5 to common is open. That was the problem. One coil is completely DEAD.

You said that you had exchanged heads betwen a 5 1/4 PC AT drive. What kind of drive should I look for ?.

Thanks in advance.

 

[geoffm3]

Let's update ....

Today I decided to swap the boards again. I put the board from the drive I can't allign anymore in a drive which is fully working.
The board worked fine. Also, I measured UF4 and got a nice signal I didn't measure the frec and Vpp. The key fact is that the signal is TOTALLY different from the one taken with the bad drive using the same electronics.

Also, I measured the head resistance (DC) of the good one. It read only 30 OHMS betwen 1 and 5 and the half betwen 1 or 5 to common. Looks like two coils with center-tapped to common

Then, I mesaured the bad mecha head and the resistance from 1 to 5 was 15K, From 1 to common only 15 ohms (OK), but From 5 to common is open. That was the problem. One coil is completely DEAD.

You said that you had exchanged heads betwen a 5 1/4 PC AT drive. What kind of drive should I look for ?.

Thanks in advance.

You'll have to find another Mitsumi or Alps (depending on which it is of course). In my case I found a donor PC Mitsumi double sided mech. The head itself was the same, but the tensioning arm was different. The mounting holes were the same, but physically they were a little different. It was a bit of a frankenstein's monster job, but it worked. I was a poor college student then with a bunch of spare parts. Today I would probably just get another 1541.

 

[SUCCESS]

Now it's very difficult to get 5 1/4 drives ....
Ok, I can buy another. I'm just annoyed with this one. I would be placed to allig this lovely drive, but without the head would be more difficult.
I'll look for a 5 1/4 FDD, but the getting a head with the hole in the position looks like impossible. Perhaps the old head need to be taken out from the tensioning arm and try to install the replacement.

 

[SUCCESS]

Lets update ...

I managed to install a head from a 5 1/4 PC FDD. A frankenstein's monster job like you said. The head was too different from the mitsumi head ASSY, so I took the head from the ASSY belonging to the PC FDD and managed to intall it on the head arm of the 1541 mitsumi.
The old head was completely removed from the arm, and the remaining hole in the arm was too big. I added plastic tabs to support the new head.
Because there was a heigth issue (the head was too far from the media that, even with the tensioning arm, the head cannot touch the media), I changed the plastic tabs four or five times. The whole head mecha needed to be dismantled each time.
Finally I get sattisfied. As soon as I finished, the drive was able to read the directory !!!!. without any care of alligment ...
Also, it read several games, but eventully hanged or failled.
I read the link above, the allingment procedure using an scope. I get the program that do half tracks with the joystick, conected an scope to UF4 differential out, and notice that the signal was stronger at the half tracks compared with the signal at the full tracks.
I moved the stepper a little until the signal at the half track dissapeared and the signal at the full track was max. Pretty easy !!!

The bad news are that the drive cannot write at all. I'm really lost with it. Any write command fail, format, rename, delete ...
The erase head impedance is only a quarter of the original. The R/W has the same impedance (I chosse this head betwen 5 head avaible from PC's FDD). I cannot get this thing working, but it was enough to feel happy that the alligment is possible !!!!!

Pedro

 

[geoffm3]

Lets update ...

I managed to install a head from a 5 1/4 PC FDD. A frankenstein's monster job like you said. The head was too different from the mitsumi head ASSY, so I took the head from the ASSY belonging to the PC FDD and managed to intall it on the head arm of the 1541 mitsumi.
The old head was completely removed from the arm, and the remaining hole in the arm was too big. I added plastic tabs to support the new head.
Because there was a heigth issue (the head was too far from the media that, even with the tensioning arm, the head cannot touch the media), I changed the plastic tabs four or five times. The whole head mecha needed to be dismantled each time.
Finally I get sattisfied. As soon as I finished, the drive was able to read the directory !!!!. without any care of alligment ...
Also, it read several games, but eventully hanged or failled.
I read the link above, the allingment procedure using an scope. I get the program that do half tracks with the joystick, conected an scope to UF4 differential out, and notice that the signal was stronger at the half tracks compared with the signal at the full tracks.
I moved the stepper a little until the signal at the half track dissapeared and the signal at the full track was max. Pretty easy !!!

The bad news are that the drive cannot write at all. I'm really lost with it. Any write command fail, format, rename, delete ...
The erase head impedance is only a quarter of the original. The R/W has the same impedance (I chosse this head betwen 5 head avaible from PC's FDD). I cannot get this thing working, but it was enough to feel happy that the alligment is possible !!!!!

Pedro

Sounds like you were at least partially successful. In my case I was able to scavenge a head from another Mitsumi mechanism so it was probably a little more compatible with the original. I wonder if you took a bulk erased floppy and attempted to format it if it would work vs. trying to rewrite a disk with data on it?

 

[SUCCESS]

There are two little differences ...

1) The head is from a HD FDD, so the erase gaps are more narrow, and so is the RW gap.
2) The erase head position in relation to the RW is different.

I have read a bit about FDD in general. Erase is used to make a blank path at each side of the data track. The erase is done while the RW head writes and forces the data to live in an small gap. That's to avoid crosstalk (interference from adjacent tracks)
The erase head gaps could be placed above and below the RW gap (a sandwich) or after the the RW gap.
The first case correspond to the C64 head ... is like a -=- and the other is like =--, where the erase gaps are after the RW gap
This type of head is the one I used. The fact is that this kind of head need to be turned on/off with some delay in relation to the write operation, while the first kind of head not needs the delay.

Now, I tried formated disks (c64 format using another 1541). Nothing.
I tried unplugging the erase ... nothing.
Format fails. but I can format the disk using a program. The program seems to be succesful, but the disk cannot be read.
and the previous information has been destroyed.

I don't know if the erase head (apart from being in different position) has too much power and erases the information writen, or it's too weak and can't succeded in making the blank gap surrounding the data track.
Also, perhaps the R/W head is a bit different (after all is a high density head).