Laser pickup: replace versus realign

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I have a friend with an admirable ethos of old-fashioned thrift; she
buys high quality items and tries to extract maximum useful service
life out of them. The other day she brought me an Alpine CDA-7837 CD
head unit from her car (the car itself has something like 300,000 miles
and is beautifully maintained). CDs apparently load but immediately
eject without playing.

I opened the case and put power to the unit. The loader is mechanically
fine. Discs load, are clamped, and spin up to what looks like correct
RPM. The laser does *not* illuminate, unless I am missing it lighting
up after the disc has covered it. I can see a bit under the edge of the
spinning disc, and there is no spillage of red light present
underneath, as I would assume would be normal.

Checked with pacparts about the laser. They have a new pickup for a
very reasonable $25. I'm certainly willing to put in the half hour it
would take to install that for my friend. But I am unsure of the next
step. Posts here about other CD units have implied that on those, after
the new pickup goes in, it must be realigned with a scope and a test
disc.

I have a scope. But the time/hassle to obtain a test disc, figure out
its use, rig the scope and do the procedure would put this over the top
to where I'd just suggest she buy a new player, thriftiness
notwithstanding.

Conversationally, a technician had told me last year that many modern
CD units no longer require a "realignment" per se. The servo and
tracking mechanisms are capable enough to run well after simply popping
in a new pickup, he said. His outfit are apparently still pleased to
bill for "realign" jobs, but that usually just translates to cleaning
the optics and turning up the bias current a bit.

Not sure how much credence to attach to that. Not sure if this Alpine
(build date 8/98) is new enough to be self-reconfiguring after a pickup
change.

Suggestions or warnings would be gratefully acknowledged!

Chris T

 

[Arfa Daily]

I have a friend with an admirable ethos of old-fashioned thrift; she
buys high quality items and tries to extract maximum useful service
life out of them. The other day she brought me an Alpine CDA-7837 CD
head unit from her car (the car itself has something like 300,000 miles
and is beautifully maintained). CDs apparently load but immediately
eject without playing.

I opened the case and put power to the unit. The loader is mechanically
fine. Discs load, are clamped, and spin up to what looks like correct
RPM. The laser does *not* illuminate, unless I am missing it lighting
up after the disc has covered it. I can see a bit under the edge of the
spinning disc, and there is no spillage of red light present
underneath, as I would assume would be normal.

Checked with pacparts about the laser. They have a new pickup for a
very reasonable $25. I'm certainly willing to put in the half hour it
would take to install that for my friend. But I am unsure of the next
step. Posts here about other CD units have implied that on those, after
the new pickup goes in, it must be realigned with a scope and a test
disc.

I have a scope. But the time/hassle to obtain a test disc, figure out
its use, rig the scope and do the procedure would put this over the top
to where I'd just suggest she buy a new player, thriftiness
notwithstanding.

Conversationally, a technician had told me last year that many modern
CD units no longer require a "realignment" per se. The servo and
tracking mechanisms are capable enough to run well after simply popping
in a new pickup, he said. His outfit are apparently still pleased to
bill for "realign" jobs, but that usually just translates to cleaning
the optics and turning up the bias current a bit.

Not sure how much credence to attach to that. Not sure if this Alpine
(build date 8/98) is new enough to be self-reconfiguring after a pickup
change.

Suggestions or warnings would be gratefully acknowledged!

Chris T

For the last 10 years, it has been rare to have to carry out alignment on CD
players after laser replacement. Very few players have even had adjustments
in them for a good many years now. If a player does need alignment, it can
be done without having to have a special test disc, All that is needed is a
good quality pressed disc ( as opposed to a home burn ). The quality of the
recorded data is quite sufficient to set EF balance, and tracking and focus
offsets if these adjustments are provided. Focus and tracking gain will not
normally require any adjustment, but these settings are not particularly
critical anyway. I have proper alignment discs, which were very expensive,
as they are ' hand ' produced, but rarely find it necessary to get them out
any more.

Have you looked on the board to see if it has adjustments at all ?

The laser in a CD player is near infra red, so there is very little visible
light emitted from it, unlike a DVD laser which burns bright red. There is
certainly not enough visible light emitted to see thru' the disc. If the
unit spins up the disc to what looks like a correct speed, chances are that
the laser is at least burning, but may be weak in output. I assume that you
have cleaned the lens ?

If the laser is that cheap, and you are confidant that it is faulty, and
that you can handle changing it, I'd just go for it. Don't forget that the
replacement will probably have a protective shorting point, bridged with a
solder blob, that must be removed before use.

Arfa