Sony CDP 707ESD skipping after a few minutes

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Guys,
Thanks for the replies but my CDP is a 707ESD with a KSS 190a laser, not an X707/X779, etc., so I think the tech info above may not apply. Right?
More info: the CD player plays fine for a few minutes then after some time it starts skipping and then stops. While it skips I can hear the laser trying to focus. It almost seems as if the issue is heat related but I'm affraid the laser might be dying. I connected a scope to the RF test point and the pk-pk voltage is around 700mv max then it goes down from there until it skips and finally stops.
Since this laser is out of production I have contemplated replacing the diode but I would like to make sure it is indeed the diode and not something else as I have also read that some people in this forum attempting to change laser diodes without success.
 
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If you keep playing the first few minutes of the disc over and over, does it continue to play ? If the laser diode were failing with heat after a few minutes then it would fail to keep playing the same section at the disc start.

When the RF signal drops in amplitude, if you track search back on the disc, does the amplitude come back again ?
 
Mooly,
Thanks for the reply. It skips any section of a disc after it's been playing for some time. For example, if I put in a disc in the morning, after the unit has been powered off overnight, then it may play an entire cd but then it may skip at the end of the cd or the beginning of the next. This leads me to believe is not laser location dependent.
As far as the amplitude is concerned, the same thing applies, it goes down regardless of location. I have noticed that it may go down to 300-400mV then it suddenly drops to nothing, causing it to skip and stop. Now, I'm not sure if the voltage drop is the caused by the laser itself, or the skipping (due to some other cause) is causing the voltage to drop.
 
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This leads me to believe is not laser location dependent.

That is what I was trying to determine. Is there a current sensing resistor in the laser drive circuitry (its usually around 10 ohms) that you could monitor the voltage across and (and so calculate the current) and compare that value to the value printed on the pickup. Sony KSS pickups usually use the last three digits of the serial number to record the current the device was factory set at. For example 42215421447 would be 44.7 milliamps. There is also a remote chance there could be an issue with any laser drive circuitry (the APC or auto power control), typically a PNP transistor driving the laser diode.

Be careful with any measurements though.
 
Sony is generally on the minimum side of the dc current through zener voltage references used in their power supplies...I would first simply parallel a resistor as described in the paper (a 47yF cap across the 4.3V zener should also help)...zener noise and differential resistance will drop considerably - it looks like a design fault...
 
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