Problem with CD tracking/starting when cold

[Jeff Wiseman]

I have an Adcom GCD-600 carousel that is moderately used and
about 11 years old. I purchased it used about 6 years ago and it
worked fine up to about 3 years ago when it started having
problems when cold. After cleaning the laser to no avail, I
replaced it with another player about 2.5 years ago so this unit
has been setting in a box. Unfortunately, since I've been out of
work for quite a while, I've had to sell nearly all my audio
stuff including the CD player I had replaced the GCD-600 with.
Now the Adcom is all I have so I'd like to try and get it going
cheaply if possible.

The problem started gradually and increased over time. When the
unit is first turned on and a disk is selected to play, A series
of clicks can be heard but the track won't start for a few
seconds. Sometimes it won't seem to start at all (or I give up
too quick). I've seen this on different tracks so I'm not sure if
track position has anything to do with it.

I've discovered that if I try other tracks until I find one that
will play, I can play it for amout 2 minutes or more and then at
that point the problem seems to have gone away. Everything seems
to start and play fine after this point. Presumably the "warming
up" of the laser may have something to do with this.

My questions:

1) What is the most likely cause of this failure? I had the unit
open once to clean the laser but that didn't help at all.
However, I didn't check the "sticky grease" or "worn out spindle" possibilities.

2) The unit IS over ten years old and the suspect "warm up" issue
of the laser implies to me that the laser is on it's way out. Is
this an appropriate assumption and a typical failure mode? This
seems to run contrary to what I've heard about CD lasers
basically working fine up to the point where they totally fail.
If this assumption is correct, I would further assume that a
tweak on the laser bias might solve the problem. Does this
thinking make sense?

3) Adcom tends to control who has access to their service
manuals--besides, I can't afford purchasing one anyway (or even
justify a cost for an 11 year old player). I am very comfortable
working with electronics but the only test equipment that I have
is a quality Fluke DMM (an old model 27). Where could I find
appropriate tracking alignment procedures and
literature/schematics for the Adcom (e.g., where are the
adjustments located, etc.)?

4) Is there any online information or general FAQ dealing with
laser alignments, etc.?

- Jeff

 

[Sam Goldwasser]

First check for gummed up lubrication.

See the CD repair guide.

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
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[Mark D. Zacharias]

The clicks are the focus ramp voltage applied to the focus coils. Repeated
clicks means focus is not being achieved on the first try. This points
strongly to the pickup.
Most pickups, likely including yours, can be replaced with little to no
adjustments after. Maybe the focus bias (focus offset) should be adjusted,
but only if you have a 'scope.

Whoever told you that cd players fail all at once doesn't know cd players.
Deteriorated performance (focus problems and general trouble playing discs)
almost always precedes a total failure.

If you do replace the pickup, be aware there is probably a "solder short"
for static protection which needs to be cleared before the new pickup will
work.


Mark Z.

 

[Jeff Wiseman]

This seems reasonable to me. However, do you have any explaination of the warm up characteristic? It's consistently a problem when cold (trouble starting some tracks) but once it has been running for a minute or two, everything seems fine. What's drifting? The laser? Or something in the servo circuitry? What's most likely to be happening here.

This may be a red herring but it seems to me that when I was last using it, when cold I would go to a track further out on the disk and it was more likely to start. I didn't spend a lot of time experimenting with this so it may only be an impression that I got. Obviously, attempting to focus on the default start track (#1) for a few moments would start to warm up the system and then moving to another track (which HAS to be later than #1) would then begin with a slightly warmed system. It's just that it always seemed to lock in very quick once I selected a different track.

- Jeff