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1541 DIAGNOSTICS
Some symptoms and solutions for a sick disk drive.
last changes or updates: 10-30-05
DRIVE DEAD... OR NEARLY
Lets take it from the top. Does the drive initialize properly when
first turned on? The startup sequence (drive does a self-test) should be:
green power light on, red drive light comes on and goes out while spindle
motor turns for a few seconds and stops. If the power light (green LED)
doesn't come on, or is dim or flickers, you have a power supply problem...
the 5 volt line is bad. That usually results in a spindle motor that runs
continuously and 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 motor will not run at all. If the drive activity light
(red LED) stays on and the motor runs continuously, it means that the
drive failed to complete the startup sequence. The most common cause is a
bad DOS ROM UB4 (901229-xx). Other chips to check are: UC4 (6502 MPU) and
UC2 (6522 VIA). The smaller "glue" logic chips are pretty rugged, but do
sometimes fail. Check UA1 (74LS14) and UD2 (7407)... they have also been
known to cause those symptoms.
DRIVE INITIALIZES OK, BUT WILL NOT LOAD PROGRAMS
When the computer is turned on, the reset signal from the computer
should cause the drive (and other periferals like the printer) to reset.
The drive red LED and spindle motor should come on and go off within a few
seconds. If that doesn't happen, suspect the serial cable (try a
substitute) or the CIA chips in the computer or VIA chip in the drive. If
the computer resets other periferals, it's probably OK.
If the computer can't "see" the drive on the serial bus, you will get
an error message: "DEVICE NOT PRESENT" when you try to LOAD something. The
default (factory setting) for a 1541 is device #8. If your drive is
hardware modified as device 9 for example, and you try to read the
directory (LOAD"$",8), you will get that error message. If the VIA (UC3)
6522 interface chip in the drive is bad, the drive will likewise be
"invisible" to the computer. Check also UB1 (7406) and UA1 (74LS14). These
two chips carry data to and from the VIA chip. When one of them fails, if
you try to load the directory (or a program), the computer will indicate:
"SEARCHING FOR $" (or program name) but nothing else will happen.
A "DRIVE NOT READY' message indicates that the computer can "see" the
drive, but there is no disk in it (or it's not formatted), or the drive
door is not closed. A dirty read/write head can do the same thing. The
drive will respond by flashing the red activity LED and banging the heads
(looking for track zero). If the computer can access the drive, but you
can't load even the directory of a known good (formatted) disk, try the
INITIALIZE command (with or without a disk inserted), then try reading the
disk again. To INITIALIZE the drive:
OPEN15,8,15
PRINT#15,"I"
CLOSE15
One quirk of the 1541 is the "drive lost" symptom. Normally, the
drive will "park" the head over the directory track (18). If the head, for
some reason, gets stuck past the directory track, INITIALIZE will return
it to track zero and it should then work normally. Note: turning the drive
off and back on again will -not- reset it if that's the problem! Some disk
errors can do that to a drive and make it look "dead", as can exiting
incorrectly from some programs by just turning off the computer. I've done
that myself a few times. As an alternative to Initializing, you could try
formatting a disk... it takes longer, but it will also return the head to
track zero. Lastly, if you insert the transit card (shipped with the
drive) with the drive turned off, it will push the head back to track
zero. Inserting a disk will not do it.
The transit card has a tab on the front (or the longer of the two
tabs if there are two) that moves the head back. Don't have your transit
card? With the top cover off and metal shield removed, you can push it
back with your finger. The drive must be turned off, of course, or the
head assembly will not move. The transit card is preferred to Initialize
or Format as you don't have to turn off the computer (just the drive) so
you don't lose the program in memory.
PROGRAMS FAIL TO LOAD COMPLETELY OR COMPUTER LOCKS UP:
If your computer setup or components have been moved recently, take
note... drives or cables too close to the monitor can sometimes pick up
interference from the flyback tranformer inside (left side of) the monitor
and garble the data. Move the drive and cables at least a foot away from
the monitor and try it again. If that helps, move the drive to the other
side of the monitor and keep the cables as far away as possible.
If you have re-initialized the drive and it still doesn't work (can't
read a disk), it may be out of alignment. Try formatting a disk and see if
it can read the (empty) directory of that disk. If it can't, clean the
head and try it again. If it can, but can't read other disks, misalignment
is a good possibility. There is one other thing you should check first:
see if the head assembly rails are sticky, especially on a drive that has
been unused for a time. With power off, the head assembly should slide
back and forth easily. If it seems sticky (experience is necessary to know
the difference between good and bad), the rails should be cleaned with
strong solvent (acetone, MEK, paint thinner) and either run dry or relubed
with a tiny amount of graphite or silicone lube. Oil on the rails will
work for a time, but eventually picks up dirt and they will get sticky
again. Avoid the use of spray cans in a drive. The spray goes everywhere.
DRIVE ALIGNMENT:
Drive misalignment is something that doesn't happen all at once. It
is a gradual process that begins with occasional errors while loading (red
LED flashing), failure to work with some programs, or excessive head
banging (the drive getting "lost" and having to go back to track zero to
"find" it's place again.) Drives are forced out of alignment (mostly while
hot from use) by copy protected programs or disk errors that cause the
head to "bang" against the track zero stop repeatedly. If the alignment is
far enough off, you will get "FILE NOT FOUND" and red LED flashing... the
drive may try several times before "giving up".
To properly realign a drive, you need special software. I use
"1541/1571 Drive Alignment" by Free Spirit Software. The flipside of the
program disk is the alignment disk, and as such, should not be copied (a
copy is only as good as the drive that made it). The program provides a
menu screen that indicates what track you're on, drive speed, etc. You
make adjustments to the drive while watching the screen. The instructions
even tell you how to load the program when nothing else will load. You can
-check- the alignment of the drive without taking it apart, but of course
realignment requires disassembly.
Drive speed can drift over time, but it's rather rare to find it off
far enough to cause problems. Spindle speed (Note: some drives have no
adjustment) is reset with a small screwdriver adjustable control on a small
PC board near the spindle motor. On older belt-driven spindle motors, the
belt may be slipping. On all drives, the spindle or collar can get sticky
and a tiny bit of lube helps. (Don't overdo it... excess oil will be thrown
off and could get on the disks).
Make sure the latch clamps the disk properly. Without a disk, move
the lever down and see if the spring presses the collar against the
spindle to clamp it securely. You can bend the tab down -slightly-
(Newtronics drives only) so it makes more firm contact if necessary. A
slipping or stalling disk will produce random read and write errors, a
problem that's very hard to track down. Some disks may work better than
others. The DD ones without a hub ring seem to slip more easily.
Bad (sticky) old grease on an ALPS drive can stall the spindle motor.
If that is suspected, you must remove the metal bar that the hub lock is
mounted on (two screws in the back) and take apart the hub lock assembly
by removing the C clip. It has half a dozen assorted washers, a brass
bushing and a spring along with the plastic hub. Don't allow those
sprint-loaded parts to fly off when you remove the C clip. These parts
need to be cleaned with solvent and put back together in the same order
as before. A bit of moly lube or light oil finishes the job.
Ray Carlsen
CARLSEN ELECTRONICS... a leader in trailing-edge technology.
Some symptoms and solutions for a sick disk drive.
last changes or updates: 10-30-05
DRIVE DEAD... OR NEARLY
Lets take it from the top. Does the drive initialize properly when
first turned on? The startup sequence (drive does a self-test) should be:
green power light on, red drive light comes on and goes out while spindle
motor turns for a few seconds and stops. If the power light (green LED)
doesn't come on, or is dim or flickers, you have a power supply problem...
the 5 volt line is bad. That usually results in a spindle motor that runs
continuously and 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 motor will not run at all. If the drive activity light
(red LED) stays on and the motor runs continuously, it means that the
drive failed to complete the startup sequence. The most common cause is a
bad DOS ROM UB4 (901229-xx). Other chips to check are: UC4 (6502 MPU) and
UC2 (6522 VIA). The smaller "glue" logic chips are pretty rugged, but do
sometimes fail. Check UA1 (74LS14) and UD2 (7407)... they have also been
known to cause those symptoms.
DRIVE INITIALIZES OK, BUT WILL NOT LOAD PROGRAMS
When the computer is turned on, the reset signal from the computer
should cause the drive (and other periferals like the printer) to reset.
The drive red LED and spindle motor should come on and go off within a few
seconds. If that doesn't happen, suspect the serial cable (try a
substitute) or the CIA chips in the computer or VIA chip in the drive. If
the computer resets other periferals, it's probably OK.
If the computer can't "see" the drive on the serial bus, you will get
an error message: "DEVICE NOT PRESENT" when you try to LOAD something. The
default (factory setting) for a 1541 is device #8. If your drive is
hardware modified as device 9 for example, and you try to read the
directory (LOAD"$",8), you will get that error message. If the VIA (UC3)
6522 interface chip in the drive is bad, the drive will likewise be
"invisible" to the computer. Check also UB1 (7406) and UA1 (74LS14). These
two chips carry data to and from the VIA chip. When one of them fails, if
you try to load the directory (or a program), the computer will indicate:
"SEARCHING FOR $" (or program name) but nothing else will happen.
A "DRIVE NOT READY' message indicates that the computer can "see" the
drive, but there is no disk in it (or it's not formatted), or the drive
door is not closed. A dirty read/write head can do the same thing. The
drive will respond by flashing the red activity LED and banging the heads
(looking for track zero). If the computer can access the drive, but you
can't load even the directory of a known good (formatted) disk, try the
INITIALIZE command (with or without a disk inserted), then try reading the
disk again. To INITIALIZE the drive:
OPEN15,8,15
PRINT#15,"I"
CLOSE15
One quirk of the 1541 is the "drive lost" symptom. Normally, the
drive will "park" the head over the directory track (18). If the head, for
some reason, gets stuck past the directory track, INITIALIZE will return
it to track zero and it should then work normally. Note: turning the drive
off and back on again will -not- reset it if that's the problem! Some disk
errors can do that to a drive and make it look "dead", as can exiting
incorrectly from some programs by just turning off the computer. I've done
that myself a few times. As an alternative to Initializing, you could try
formatting a disk... it takes longer, but it will also return the head to
track zero. Lastly, if you insert the transit card (shipped with the
drive) with the drive turned off, it will push the head back to track
zero. Inserting a disk will not do it.
The transit card has a tab on the front (or the longer of the two
tabs if there are two) that moves the head back. Don't have your transit
card? With the top cover off and metal shield removed, you can push it
back with your finger. The drive must be turned off, of course, or the
head assembly will not move. The transit card is preferred to Initialize
or Format as you don't have to turn off the computer (just the drive) so
you don't lose the program in memory.
PROGRAMS FAIL TO LOAD COMPLETELY OR COMPUTER LOCKS UP:
If your computer setup or components have been moved recently, take
note... drives or cables too close to the monitor can sometimes pick up
interference from the flyback tranformer inside (left side of) the monitor
and garble the data. Move the drive and cables at least a foot away from
the monitor and try it again. If that helps, move the drive to the other
side of the monitor and keep the cables as far away as possible.
If you have re-initialized the drive and it still doesn't work (can't
read a disk), it may be out of alignment. Try formatting a disk and see if
it can read the (empty) directory of that disk. If it can't, clean the
head and try it again. If it can, but can't read other disks, misalignment
is a good possibility. There is one other thing you should check first:
see if the head assembly rails are sticky, especially on a drive that has
been unused for a time. With power off, the head assembly should slide
back and forth easily. If it seems sticky (experience is necessary to know
the difference between good and bad), the rails should be cleaned with
strong solvent (acetone, MEK, paint thinner) and either run dry or relubed
with a tiny amount of graphite or silicone lube. Oil on the rails will
work for a time, but eventually picks up dirt and they will get sticky
again. Avoid the use of spray cans in a drive. The spray goes everywhere.
DRIVE ALIGNMENT:
Drive misalignment is something that doesn't happen all at once. It
is a gradual process that begins with occasional errors while loading (red
LED flashing), failure to work with some programs, or excessive head
banging (the drive getting "lost" and having to go back to track zero to
"find" it's place again.) Drives are forced out of alignment (mostly while
hot from use) by copy protected programs or disk errors that cause the
head to "bang" against the track zero stop repeatedly. If the alignment is
far enough off, you will get "FILE NOT FOUND" and red LED flashing... the
drive may try several times before "giving up".
To properly realign a drive, you need special software. I use
"1541/1571 Drive Alignment" by Free Spirit Software. The flipside of the
program disk is the alignment disk, and as such, should not be copied (a
copy is only as good as the drive that made it). The program provides a
menu screen that indicates what track you're on, drive speed, etc. You
make adjustments to the drive while watching the screen. The instructions
even tell you how to load the program when nothing else will load. You can
-check- the alignment of the drive without taking it apart, but of course
realignment requires disassembly.
Drive speed can drift over time, but it's rather rare to find it off
far enough to cause problems. Spindle speed (Note: some drives have no
adjustment) is reset with a small screwdriver adjustable control on a small
PC board near the spindle motor. On older belt-driven spindle motors, the
belt may be slipping. On all drives, the spindle or collar can get sticky
and a tiny bit of lube helps. (Don't overdo it... excess oil will be thrown
off and could get on the disks).
Make sure the latch clamps the disk properly. Without a disk, move
the lever down and see if the spring presses the collar against the
spindle to clamp it securely. You can bend the tab down -slightly-
(Newtronics drives only) so it makes more firm contact if necessary. A
slipping or stalling disk will produce random read and write errors, a
problem that's very hard to track down. Some disks may work better than
others. The DD ones without a hub ring seem to slip more easily.
Bad (sticky) old grease on an ALPS drive can stall the spindle motor.
If that is suspected, you must remove the metal bar that the hub lock is
mounted on (two screws in the back) and take apart the hub lock assembly
by removing the C clip. It has half a dozen assorted washers, a brass
bushing and a spring along with the plastic hub. Don't allow those
sprint-loaded parts to fly off when you remove the C clip. These parts
need to be cleaned with solvent and put back together in the same order
as before. A bit of moly lube or light oil finishes the job.
Ray Carlsen
CARLSEN ELECTRONICS... a leader in trailing-edge technology.