On 28/08/2013 11:00, Arfa Daily wrote:


"Mark Zacharias" wrote in message
...
"N_Cook" wrote in message
...
Neither me or owner will spend out on a new optical unit (failed
laser), big spondulics. But a near industry standard KSS 213C looked
somewhat similar , so I tried it out. This one laying around ,
unknown condition, from some scrapped something. The ribbon feed
lines for the 3 laser pins matched , the other 2 deck motor+switch
leads matched up, so tried it out. Laser lit but logic of the end
stops wrong so swapped the optical unit across to the original
(scrapper would not have mechanically fitted in the Denon anyway).
Required some bodging to fit, straightforward but too much for
detailing here, but sledge etc worked .
Adjusted power pot and cleaned lens and now consistently reads data
track and plays about first 2 minutes track1 of any CD I try,
faulters and stops, will not play any track 2 or higher.
I suspect the registration of the centre limit switch is out, but
could be a problem with the rack although powers up and down the
slide without incident with only 2 volt on the motor, but I will try
marking rack and cog of the 2minute stoppages. I assume a new (cheap)
KSS 213 would show the same stoppage.
So how to adjust the end stop , ? pieces of shim material added and
subtracted in the gap between sledge and leaf switch and suck it and
see? or some other problem likely?


I think this is a sled motor issue; I have never seen any limit switch
other than the inner (start) switch. As the tracking coil reaches it's
physical limit, a player will skip or "falter and stop" just like you
describe, if the sled does not advance.Check the voltage across the
sled motor as this process unfolds. At some point the voltage should
increase to kick the sled forward. Maybe there's a mechanical
obstruction, maybe you still have wiring issues.

Mark Z.


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


Arfa,

Sorry to gate crash the thread, just wondering if you got my email
regarding the Yammy amp-tuner, the Samsung Telly and the Panny Freeview
DVD recorder?

Regards,

Stephen.