Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old May 17th 08, 10:49 PM posted to sci.electronics.repair
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Default Sharp CD-PC651 No disc

The cd lens on this unit trys to focus on the disc but there is no
beam from the lens. How do I check the lens?

Thanks

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Old May 18th 08, 12:16 AM posted to sci.electronics.repair
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Default Sharp CD-PC651 No disc

Jack00 writes:

The cd lens on this unit trys to focus on the disc but there is no
beam from the lens. How do I check the lens?


If there is no beam from the lens, then the laser is either dead or not
being turned on.

But, the laser in a CD player is 780 nm, near IR, and close to invisible.
It's not bright like a DVD player's laser. Just a faint red dot in the
when viewed from the side.

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Old May 19th 08, 01:30 AM posted to sci.electronics.repair
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Default Sharp CD-PC651 No disc


"Jack00" wrote in message
...
The cd lens on this unit trys to focus on the disc but there is no
beam from the lens. How do I check the lens?

Thanks


The laser in a CD operates at near-infrared, so emits little visible light.
With the lens area shaded, and looking across the top of it at an oblique
angle, you should just be able to see a little 'sparkling' red light in
there, whilst the focus search is taking place. If you do see the light, and
the lens is clean, but the disc either never spins up, or spins endlessly
without ever reading the TOC, or stops with a "NO DISC" message, then it's
very likely that the laser is faulty. The only 'real' test for a defective
laser is to try a replacement. If you cannot see any red light at all in the
lens, then it's not burning, and the commonest causes of that are either a
defective laser diode within the optical block, or a bad cable to the
optical block. The flat white flexiprint type has a habit of fracturing
across one or more tracks, right by the blue reinforcing strip at one end or
the other. Types using conventional wires tend to fracture inside the wire's
plastic sleeve, close to where it is crimped into the connector pin in the
plug body.

Although the output power of a CD laser is in the 'eye safe' category, I
still would not recommend looking straight down into the lens ...

Arfa




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