CD beam focus function query

How much is "plenty"? :)

Doubt it. Unless you mean from laser diode to LED. ;( :)

Doesn't sound like there is any light to the PDs.

P.S. I assume this is with a disc in place. :)

--- sam | Sci.Electronics.Repair FAQ:

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

started

the

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in the

Dropping the power pot R down from 1600 ohm down to 500 ohm, the spinner kicks in and plays without hiccup. I had a root around inside the optics area and there was a cocoon of an insect inside an otherwise empty and non functional section of the plastic housing of the optics, but I don't think that was anything to do with the problem . Serious drop in laser output ?

Probably, or the insect was walking around on the optics and leaving crud behind before it spun its cacoon. :)

--- sam | Sci.Electronics.Repair FAQ:

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

Might be a serious drop in laser power, or dust on the critical angle mirror inside the optics. On one particular JVC laser - the Optima 150S / 6S - by pushing the lens gently to one side, you can actually see the mirror, and there's just enough space to get a dry cotton bud down the side, to clean the dust off. This invariably restores these particular lasers to full output and functionality, without having to resort to adjusting the laser current. However, this is the only laser that I know where you can actually do this. In my experience, laser diodes are very critical of their drive current, and turning them up usually results in total failure in fairly short order, so it's only useful as a diagnostic measure, and should not be used as a customer-chargeable repair method. If turning the laser up restores reading, just replace it. I do not recommend trying turning up DVD lasers, even as a diagnostic measure..

Arfa

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Silliest fault/syptom I've seen for a long time. When I originally took the optical section apart, down an inch long narrow shaft by veiwing angled and just about getting light down there, I saw a delicate facetted mirror like a cut diamond which seemed like I supposed it should. I re-opened it today and thought I'd wind up some cottton into a long thin string , douse in meths and clean this delicate facetted lens. Looked again and the facets had disappeared , it was probably a minute piece of iridescent insect wing that had been lodged there. Returned power pot back to original setting and fine , also the 7808 is not running hot supplying the laser. A bug in the system.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

You stole my line. :)

--- sam | Sci.Electronics.Repair FAQ:

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