"Rob" wrote in message
ups.com...
I'm repeating my post here, but there is a photo also, showing the E-
F, E-off and F-off pots.

***
So I open her up for an inspection. First off, whats inside:

DAC: BB PCM54HP
Optical Assy: KSS-152A
Rubycon caps
Motors: pickup sled and tray drive: RF-510T; spindle drive:
RF-310T-1?? Mabuchi
The tray is belt driven and is clearly dry and slipping.

The lens looked clean, but I went ahead and dabbed it down with 99%
Iso, also air cleaned the mirror. The assy slides smoothly across the
two sled bars.

I connected/disconnected all connectors.

Still, same problem. Seems to always be able to read the startup
information (number of tracks, total time), but still occassionally
cannot lock on a track when FF or Rev.

It has been suggested to possibly adjust the E-F. Is this advisable?
Here is a photo of the pots available.

Any idea how I can get to that belt? There is a screw with suspension
on the far end of the transport, but I can't seem to guess how to take
her out. The face of the tray appears to be permanently mounted.

***

Apparently, this generation of deck has some intermittent problems
with tracking and skipping. Every deck I've seen on eBay is "working
perfect", but sold in "as is" condition, so there is the suspicion
that other owners are experiencing these issues and not being
forthcoming with them (as in my experience).

My problem does not seem significant, I can play straight thru and am
not experiencing skipping, just the occasional inability to lock onto
a track when using the skip track function. It may not make sense to
tamper with it much at this point, though I am going to have to
replace the belt. I also have the Dick Smith ESR meter, do you think
it would be worth checking the caps? Seems that if this issue is that
type that gets worse over time, that it be something like cap
degradation? Should I concentrate on the caps around the adjustment
pots, perhaps?

Also, in general, if I were to change a laser on a cd deck and the
laser is the problem (may or may not be here), is this usually a "drop
in" job with no further adjustments? I don't have a scope, but do
have most other instrumentation.

If I were to adjust the E-F pot and mark the original position, is it
very likely that I will at least be able to get back the operability
that I currently have? Would be a shame to tamper with it then end up
in a worse situation. What about cleaning the pots, can dirty pots
cause these symptoms? You should be able to go to that site to see my
type of pot (trim pot, haven't really checked for manufacturer),
perhaps you have a cookie issue, it is not the type of site that
requires registration.

Thanks for the help, I had not come across that E-F adjustment
procedure, I have a pair of stethoscopes that could assist in hearing
the symptoms you describe are needed for adjustment.


You shouldn't need anything other than the naked ear to be able to hear the
servo noise. I would not recommend adjusting any pots marked "offset" as you
really need to follow manufacturer's procedures to adjust them, but you will
be fine with E - F balance and tracking and focus gain. Although E - F
balance can be quite critical for proper tracking performance, it's not so
critical that a few degrees either side of right, will stop the player from
running. You would certainly be no worse off by just returning the pot to
its original position. All that this pot is doing, is balancing the opamp to
which the "E" and "F" pickup diodes are connected. These two diodes are
responsible for keeping the laser's beam running down the centre of the
track. If both diodes were perfect, and the beam collating and focusing
optics were perfect, then when the beam was centrally on the track, the
outputs from the diodes would be identical. Unfortunately, none of these
things is perfect, including the opamp itself, so the balance pot is
provided to compensate for all the imbalances, and allow the opamp to
produce a net zero output when the beam is centrally on the track. If the
balance is not set correctly, the beam will be slightly off to one side or
the other, which will reduce the level of signal read from the disc, and can
result in poor quality tracking servo data being extracted, which will make
the servo's performance poor. If the beam is off to one side or the other,
the tracking servo will be working hard, and this is the raised servo noise
level that you can hear.

As far as replacing a laser goes, if you use a genuine replacement, they are
usually just drop in. Cheapo second source types may be a little less
forgiving, and require you to set E - F balance.

If you have an ESR meter, and the caps are conventional through-board
electrolytics, then by all means check them all. A degree of 'feel' is
needed to interpret the results for small low value caps, but I guess if you
have a meter, then you are experienced enough with it to know this. There
are a couple of older Sony models which used to suffer the sorts of problems
that you are experiencing as a result of poor caps. When you do a track
jump, the gain of the servo is knocked down to stop it resisting, and then
back up again when it reaches where its going to achieve a quick re-lock.
There are caps attached to the servo processor IC, which are involved with
this procedure.

Arfa