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c64 1541 alignment instructions - (nf) [message #72563] Sat, 25 May 2013 10:35
miller is currently offline  miller
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Message-ID: <16800013@uiucdcsb.UUCP>
Date: Fri, 14-Sep-84 00:56:00 EDT
Article-I.D.: uiucdcsb.16800013
Posted: Fri Sep 14 00:56:00 1984
Date-Received: Thu, 13-Sep-84 07:37:44 EDT
Lines: 77
Nf-ID: #N:uiucdcsb:16800013:000:4714
Nf-From: uiucdcsb!miller    Sep  7 23:56:00 1984

#N:uiucdcsb:16800013:000:4714
uiucdcsb!miller    Sep  7 23:56:00 1984

There have been several notes on the net recently concerning the c64 1541 in
general and alignment problems in particuar.  I didn't have time to post this
in the past, but now I've got a little more spare time so I'll describe briefly
how I align my disk.  One note though: the "official" way to align your drive
is with a scope and some adjustments on the bottom.  However, it has been my
experience, and that of my friends, that the bottom adjustment is not the cause
of bad alignment most of the time.  Although it can be used as a solution,
since it is not the problem, why do it that way?  Especially since correcting
the real problem is much simpler and cheaper to do.  Both methods will work,
however.  And depending upon how much you use your drive, the fix should last
from one month to a year.
How do you know your drive is out of alignment?  Well, if your red light blinks
often while reading/writing disks, and you sometimes get load errors, then you
probably are in trouble.  Run the following program on a disk you *know* was
written aligned, e.g., a factory written disk like the test/demo disk included
with your 1541.  If the red light comes on steady with no blinking, then your
drive is ok.
10close2:close15:open15,8,15
20open2,8,2,"#"
30fors=0to10:fort=1to35
40print#15,"u1:";2;0;t;s
50?"track"t"  sector  "s
60next:next
70close2:close15
First, you need to get inside your drive.  Take off the top case (screws on the
bottom).  Next, take off the top front metal shielding (screws on left hand
side).  You are now looking at the pc board on the top.  Unplug the wires that
connect to that pc board (slits on the connectors are on the inside - remember
this when plugging them back in).  Now you can take off the pc board (screws on
the top and 2 on the right by the heat sinks).
I should really draw a diagram for what follows, but I don't have time so try
to follow this while looking at your drive.  In the middle is the read/write
mechanism.  It slides forward/backwards on those 2 rods.  The black wire coming
from the right goes into the back of this section.  On the right is a metal
band.  It connects to the read/write assembly.  It also loops around a pully in
the front (pully is held back by a spring) and in the back (the one that has
the 2 metal stops on the top).
It is in this circular metal band that most of the problems arise.  The first
problem I encountered was with the rear pully/2 stops.  The stops hit up
against the tab, which limits movement for the read/write head in either direc-
tion.  Rotate this pully.  You will notice that since it is connected to the
metal band (via a screw) and the band is connected to the read/write head, the
read/write head will move back and forth.  Now with me, the constant pounding
of those stops against that tab (during a NEW - remember that clicking noise?)
had moved the tab sideways.  Thus, the r/w head was being limited by the front
of the rod assembly - not the right stop.  The solution here is to readjust the
tab up top (single screw) and move it so that the pully stop hits it before the
r/w head hits the front.
A much more common problem is that the spring for the forward pully isn't quite
strong enough.  The simple solution here is to gently move it forward and back
a bit (band will go slack) and then pull it towards the front until the band is
quite taut.  Be careful to keep the pressure centered, or you'll pull the right
rod out of its guides.  Amazingly, this simple procedure is all it needs 95% of
the time.
You want to check this when you're done by running the above program.  The red
light should be steady if you've done it correctly and the disk was written on
an aligned drive.  Disks written on a nonaligned drive should now give you
trouble, so try and not let your drive get too far out of alignment.
One more word of caution.  When the 1541 overheats, many things happen, not the
least of which is that the band expands (I joke that it's a bimetalic strip).
Even aligned drives will give you problems then, so try and keep your drive
cool.  I usually keep the top cover off if I intend to use it for very long.

This entire procedure takes about 10 minutes (once you get used to it).  I find
it a lot simpler than playing with the adjustment screws on the bottom of the
drive.  Plus, all you need is a philips head screwdriver.  Of course, in the
rare event this procedure does not work, you'll have to go at those adjustment
screws on the bottom.  But that's never been the case for me (yet).
Remember to ground yourself out for static charges if you have a carpet before
starting all of this.  And good luck.  You shouldn't have too many problems if
you're careful.

A. Ray Miller
Univ Illinois
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