Laser Pickup Failure Modes ? - diyAudio
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Old 29th January 2003, 11:07 PM   #1
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Default Laser Pickup Failure Modes ?

During my career, I have replaced hundreds of defective laser pickups.
Whilst some have emitted no laser light, the vast majority do emit light but will not work correctly.
In these cases, the cdp may load TOC, but then not play, or will load TOC and play, but mistrack easily on various discs or when the player is bumped.
Examination of the HF waveform reveals dirty signal in some cases, but not all.
Any references to a definative study of what causes laser pickup assy failure ?

Eric.
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Old 30th January 2003, 06:35 AM   #2
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Lightbulb Laser Failure

Hi Eric,
Never agreed more with a post. This laserfailure is a tricky business.
Very often the eyepattern looks OK on the scope but the player mistracks and skips. The only thing I could see is that the amplitude goes down but that is also not always clear.
We crancked up the output of some lasers to help the custumer but these came back in a few weeks, then claiming warrenty!. Never do that again. A built in servicehour counter would be a nice thing.
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Old 30th January 2003, 06:42 AM   #3
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The photodiode array may have one or more worn out segments.
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Old 30th January 2003, 07:40 PM   #4
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All solid state laser diodes do wear out after an amount of service time. In the laser cavity of the diode will come very tiny cracks after time. When there are sufficient cracks there is insufficient “Lasering” left. Also the light output of the LED exiting the laser cavity will drop after time. This you can see at a too low EFM signal.

I cranked up the laser of my Sony CD player when it started skipping and served me another 4 years. But that is luck. Most time the laser is definitely gone within a year or so after such an adjustment. It is always best to replace the complete laser head in such cases.

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Old 31st January 2003, 08:32 AM   #5
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When we measure the RF and all looks ok, we take out the axe, clean it with methanol and lubricate it again. In many cases the axe is also the reason of failures. The spindle motor is sometimes a problem too. In some old Pioneer's we replaced it together with the lens. In some Sony drives we always replace the small flat cable as well. If possible I replace the whole drive. As an example, I can by the KSS213C laser unit + drive cheaper than the laser unit without drive. But, as stated, they can be tricky.

Hugo
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Old 1st February 2003, 03:44 PM   #6
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Default Laser diode replacement

Does anybody know of any replacement for the laser in the Philips CDM-1 transport?

ckt
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Old 1st February 2003, 04:59 PM   #7
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Default Re: Laser diode replacement

Quote:
Originally posted by diyman
Does anybody know of any replacement for the laser in the Philips CDM-1 transport?

ckt

http://www.blackpudding.fsnet.co.uk/...lips_laser.htm is a good reference site for everything about lasers.

/Hugo
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