On 29/08/2013 01:34, Mark Zacharias wrote:
"N_Cook" wrote in message
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On 28/08/2013 11:00, Arfa Daily wrote:


"Mark Zacharias" wrote in message
...
"N_Cook" wrote in message
...


I would agree with everything that Mark says. The lens tracks across the
disc with a sort of 'wave' motion, the 'fine' part of this process being
handled by the lens tracking coils, and the 'coarse' part by the sled
motor and associated gearing. The time between motor 'roll-ons' varies
from player to player, but is typically between about 4 and 10 seconds.
If you monitor the voltage across the motor during each period, you will
see it ramp up gently until the point is reached where the motor rolls
over one or two commutator segments. If all is well with the servo, the
motor and the mechanics, there should be no overshoot, but often there
is, and the motor will roll back a little. When I am looking for this
specific problem, I always mark some radial lines on the large top-side
drive gear with a Sharpie pen. You can then watch the behaviour of the
coarse tracking operation, doing a rough count between roll-ons. If you
see the time varying a lot, there is usually a mechanical problem with
either the motor or gear train. If you see it taking a long time to roll
on round about where you are expecting it to give trouble, you can try
helping it along by giving the gear a gentle poke in the direction it
should move. If that keeps it playing, then there you go. Maybe the sled
motor on the original deck is poor. You could always try the old trick
of squirting a drop of switch cleaner in the holes at the back, and then
'blasting' it very briefly several times in each direction with 12
volts. That will usually clean up the comm and brush gear enough to get
it running smoothly again, proving the point that you need to replace
the motor.

You might also check the performance of the spindle motor, as this can
also cause tracking problems if it produces enough data jitter. Also,
try selecting a track well into the disc, before pressing play, and see
if it goes there ok and plays through the track, or gives trouble again
a couple of minutes in. 'Lumpy' spindle motors tend to behave better on
later tracks where the rotation speed is less. Looking at the eye
pattern on a scope can tell you a lot about tracking and jitter
behaviour. The same 'clean it and blast it' technique can also be used
on spindle motors to temporarily recover them to prove the point

Arfa

I changed the position of the central limit switch action point by
1.2mm and the same play for 2 mins only.
The Denon optical unit , marked Sanyo, does not use the usual
double-rack anti-backlash arrangement but a much cruder sort of sprung
plastic arm tensioner via the mount of the final double cog. I had to
remove the second rack on the KSS213 to fit in the available space.
The tension is now too high, the rack must be .5mm or so wider, and
I'll have to find a way of backing off the tension. The final cog to
the rack is 12 teeth and I can feel resistance 12 times a rev. Running
the motor continuously , even at low V,the inertia overcomes that
lumpiness, but that is not representative of the normal radial
stepping drive, as you say.


I guess I kind of missed the point of replacing a Sanyo laser with a
used Sony.

Bad idea - be surprised if you ever get it to work right, at least with
any acceptable combination of parts cost and time/effort.

'nuff said.

Mark Z.

The Denon optical unit is labelled CD11FTA3N , unless you are aware of
its Sanyo number , they are expensive to replace, presumably specials
produced by Sanyo and consequential markup.