Posted By
BushRat
on 2002-07-18
|  Optical stop
I could duplicate the directory read errors, you are describing, on my 1551 that I dug out. I had to move the optical stop block, to intentionally mis-align the drive. The mech assy in mine is a Newtronics, from a 1541. The original drive assy and the other 1551 board are with Dave Cook in California. This is my secondary unit that was simply a 1551 board that I mounted in a 1541 Newtronics case. Luckily, I've not had a problem with it. I snapped a few pix and uploaded them to my wife's page at:
http://home.gci.net/~ace/files/
They show the mechanical and optical stop assemblies, along with the motor speed adjustment control (the little blue adjustment control). If you loosen the two holding screws on the black optical stop assy and nudge it (just slightly!) toward the rear of the case, you may cure your problem... if it is alignment. The optical stop was installed to prevent the hammering that the Commie drives used to go through, when trying to align themselves after a fault and during initialization. If the optical stop is too far forward, the drive thinks it has reached the end of the head travel before it actually reaches the true mechanical stop. That can result in the drive being "soft misalligned" and can make the reading of track 18 (the directory track) difficult. Remember, that Commie screwed up by allowing the "rest" position of the read/write head to be at track 18. That is why we all learned to avoid turning the drive on or off with a floppy inserted and the head locked down (unlike PCs) the turn on/off cycle produced a pulse at the R/W head and easily garbaged (blew) the directory. Funny how this stuff sticks in one's head after all these years.
This may not be your answer, but worth a check. Don't hesitate to try a new drive assy from a true 1541 (the white unit shown in one of the pix) as long as it is a Newtronics (not the
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