Adcom CD player, help needed

[Lee]

Just replaced the laser assembly on an Adcom GCD-575 player (original
was a Sony KSS-150A and replacement was KSS-210A) since the laser was
weak and causing the player to skip on some CDs. Now, however, the
player has trouble even recognizing CDs! It seems that a tracking
adjustment is needed following a laser change, but looking inside the
adjustment pots are not identified (except for one as "EF"); there are a
number of testpoints (TE, FE, FEBI, VCO, FO, TR) but again what is the
corresponding pot to adjust? Can anyony help? I've previously adjusted
several Pioneer players using the Sci.electronics.repair FAQ procedure
but wasn't able to figure out the Adcom. I e-mailed Adcom, but no reply
yet. All comments welcome.

[Mark D. Zacharias]

Well, you're really going to need an oscilloscope and the service manual to
adjust these. If the others haven't been messed up too much, I would suggest
the FO (focus offset) is the one most likely to help. It relates to the
actual HF signal read from the disc. The adjustment is done by observing on
a 'scope and adjusting for the biggest and best-defined looking waveform.
You can probably find an example of this waveform by doing a Google search
for, "cd eye pattern".
You can use most any good quality disc for your tests, but you should
confirm by trying several discs to help ensure compatability.
The TE (tracking error) adjusts the gain through the tracking servo portion
of the circuit. There's different methods here, but one I'm comfortable with
also uses a 'scope, adjusting the random-noise looking waveform back and
forth, you would see that towards one end there's more low-frequency
content, then when the pot is turned the other way, there's more
high-frequency content. Balance the low and high near the middle of the
pot's rotation.
The FE is usually adjusted for the minimum number of small "ticks" at the FE
test point, as viewed on a 'scope.

Hope this helps.

Mark Z.


"Lee" > wrote in message
...
> Just replaced the laser assembly on an Adcom GCD-575 player (original
> was a Sony KSS-150A and replacement was KSS-210A) since the laser was
> weak and causing the player to skip on some CDs. Now, however, the
> player has trouble even recognizing CDs! It seems that a tracking
> adjustment is needed following a laser change, but looking inside the
> adjustment pots are not identified (except for one as "EF"); there are a
> number of testpoints (TE, FE, FEBI, VCO, FO, TR) but again what is the
> corresponding pot to adjust? Can anyony help? I've previously adjusted
> several Pioneer players using the Sci.electronics.repair FAQ procedure
> but wasn't able to figure out the Adcom. I e-mailed Adcom, but no reply
> yet. All comments welcome.
>
>

[Mark D. Zacharias]

P.S.

DO NOT ADJUST THE VCO without a service manual and a frequency counter.

mz


"Lee" > wrote in message
...
> Just replaced the laser assembly on an Adcom GCD-575 player (original
> was a Sony KSS-150A and replacement was KSS-210A) since the laser was
> weak and causing the player to skip on some CDs. Now, however, the
> player has trouble even recognizing CDs! It seems that a tracking
> adjustment is needed following a laser change, but looking inside the
> adjustment pots are not identified (except for one as "EF"); there are a
> number of testpoints (TE, FE, FEBI, VCO, FO, TR) but again what is the
> corresponding pot to adjust? Can anyony help? I've previously adjusted
> several Pioneer players using the Sci.electronics.repair FAQ procedure
> but wasn't able to figure out the Adcom. I e-mailed Adcom, but no reply
> yet. All comments welcome.
>
>