CD Laser - Last Chance or Last Rites

[N Cook]

Just checking to see if anyone knows of a 'CPR technique' .
Player would sometimes play a CD from cold but never a second CD.
The cherry red laser output would drop off over time just by sight.
To confirm a laser problem not controller problem I powered
up via external supply and droppers. Also monitored light output
with an IR phototransistor and ohms DVM.
Confirmed emission drop off and voltage at the laser dropping
from 2.64V to less than 2.5V. Gonner ?

electronic hints and repair briefs , schematics/manuals list on
http://homepages.tcp.co.uk/~diverse

 

[Sam Goldwasser]

Just checking to see if anyone knows of a 'CPR technique' .
Player would sometimes play a CD from cold but never a second CD.
The cherry red laser output would drop off over time just by sight.
To confirm a laser problem not controller problem I powered
up via external supply and droppers. Also monitored light output
with an IR phototransistor and ohms DVM.
Confirmed emission drop off and voltage at the laser dropping
from 2.64V to less than 2.5V. Gonner ?

Probably but the method of powering it using resistors, etc., isn't a fair
test as the output power will drop off as it heats up. The driver in the
CD player is supposed to maintain the output power constant, but apparently
isn't able to.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
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| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

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[Mark D. Zacharias]

Cherry red? Is this a dvd player?

Mark Z.

 

[N Cook]

I had already established that the front end feedback circuit
to the laser power control was working if enough signal
got to its photodiode, so either a prob with this diode
or the laser. Last Rites ?

 

[Sam Goldwasser]

I had already established that the front end feedback circuit
to the laser power control was working if enough signal
got to its photodiode, so either a prob with this diode
or the laser. Last Rites ?

Yeah, probably.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.