| Posted By
Hans
on 2012-06-08
02:54:38
|  1551 maintenance
I got a 1551 floppy which isn't operational.
The device powers up, it is being reckognized by the Plus/4 but fails to read/write any diskette. I cross-checked the diskettes with a 1541 - they are readable and can be "headered", and files can be loaded from them and can be saved to them.
I guess that the the 1551 read/write head is either stuck with dirt and/or needs adjustment.
Does anybody here have experience with inner cleaning & maintenance of a 1551 floppy?
In the old days, there were cleaning diskettes on sale (similar to cleaning disks for CD/DVD) - some disk size circular wick inside a floppy cover which was to be soaked with a cleaning fluid and to be run several spins. Unfortunately, such tools aren't available anymore.
Thank you for any hints!
Regards,
Hans.
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Posted By
SVS
on 2012-06-08
03:07:59
 | Re: 1551 maintenance
If you hear repeated knocks, then it is a misaligned header and you can use a plastic screwdriver to fix (it is existing a program to help the operation).
If you don't hear the reset knocks during attempt to read, probably the header is fault or some other electronic component. In this case you can substitute the whole mechanism from a 1541.
Last case is the cartridge socket fault, since it has ICs inside. This case is the worse one, because the spare components are difficult to find and to unsolder.
Let us upadate.
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Posted By
Chicken
on 2012-06-08
03:54:40
 | Re: 1551 maintenance
Do you have another working 1551 drive? Then you should test the drive mechanism and the paddle (that's the cartridge that connects to the plus/4) separately with the working parts. Everything can be disconnected without soldering 
From what you posted, it seems like the paddle is ok. If you are lucky then it's just a misaligned head (though, from experience, this is not a typical 1551 problem). I'm not into electronics but some time ago crock posted how you can check if the head is defunct.
http://plus4world.powweb.com/forum/22065
"If you think the mechanism is trashed, check the resistances across the wires to the read/write head. It should be between 12 and 25 ohms across any combination, anything significantly higher means the head is toast."
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Posted By
MIK
on 2012-06-08
06:41:08
 | Re: 1551 maintenance
Something I've always wondered.
In the case of a 1541-II which I currently use.
Rather than having the drive powered up for ages not being used I tend to switch it off after I have loaded the software if the drive is not going to be used again for a while.
Only powering it up again when the Plus/4 is off.
Other than a little wear to the power switch over time is it safe to do this meaning it will not harm the Plus/4 switching the 1541-II off while the Plus/4 is running?
I just hate the idea of the the drive sat there doing nothing while powered up.
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Posted By
Hans
on 2012-06-08
07:15:20
| Re: 1551 maintenance / 1541-II
@ Chicken & SVS
Thank you for the hints. I think I'll try the maintenance/adjustment program first, hopefully the problem can be solved that easy. Can't do it rightaway but there's an XM1541 cable on its way to me so that I can transfer the prog to Mr. Commodore. Will keep you updated after having done the test.
No, I don't have a second 1551. I have, however, a 1541-I (size the same as the 1551). This one went dead the other day - no pilot light, no humming. The fuse is OK but I suspect that the internal PSU is blown. Perhaps I can cannibalize this rig to fix the 1551.
@ MIK, I found that all the PSUs of the Commodores I got here are a little somehow active even when running idle, i.e. no floppy / computer switched on.
To minimize the risk of early wear of the PSUs, I'm going to add switches to each power lead, including a "zero-voltage" filter. I don't know the correct English term for such a device. In general, its a thyristor or a triac which opens the circuit only after the AC current is down at zero volts. - You probably have watched sometime blowing of a light bulb **FLASH!!!*** when switching on the light although the bulb was totally OK.This quite often happens when the voltage is at peak = 240 VAC in the UK, 230 VAC in Continental Europe.
So, I would recommend to have the device's on/off switch always open and to activate it by a switch next to the plug.
Regards,
Hans.
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Posted By
MIK
on 2012-06-08
14:02:16
| Re: 1551 maintenance
Thanks Hans.
Indeed I always unplug my old machines from the mains when not in use and yes the power adapter can go just as easily as the main board inside the drive.
As time passes it may become much harder to replace stuff. My two drives have served me well but for years now I only use one at a time while one stays in storage.
I hope your 1551 comes good! Don't forget to give the cartridge pins a good clean, just like the contacts found in the keyboard they can become dirty over time. Good luck!
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