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polaret
Joined: 23 Oct 2004 Posts: 90 Location: greece
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Posted: Tue Jan 31, 2006 3:06 am Post subject: Samsung laser pick up |
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Hello i have a samsung MAX 440 and i think i have problem with the laser (SOH AP)doesnt work at all, i replace it but i fount only (SOH APU)is it the same ? because i replace it and now when i put CD turning and doesnt recognise anythink.
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Baeteman Guest
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Posted: Mon Feb 06, 2006 2:43 am Post subject: |
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Hi there,
great care must be taken by replacing laserunits. Mostly, and i mean
almost always, a unit with a different typenumber cannot be used instead. At least i had some bad experiences in the past.
In general, the detection goes as follows:
When the tray closes, or play is pushed, the laser is switched on
and tries to find focus on the innerpart of the disc.
This action can be seen as the moving up/down from the lens for a
few times.
Also try to see if the laser is on. Do this in a darkened room and
look to lens at some distance, say from aside but not directly into it.
Some red hue should be seen, meaning the laser is on.
If focus is found, the spindlemotor should start turning, while the sled-
motor moves the optical block inwards in order to read the indextracks.
Try to find out if the spindlemotor gets power. (a few volts)
Sometimes there is a problem with on of the motors, meaning that
through contamination in the collector, caused by wear of the
carbonbrushes, the latter draws too much current, or simply refuses
to run.
Disconnecting them en "feeding" them with an external supply can
show what is happening. If contamination is suspected, this can be
seen on the current drawn by it. Increasing the supply for a few
moments usually "burns" away this contamination.
If the laser is at the "end of it's life, this can only be checked by the
diagrams. A certain voltage can be measured in the series resistance
with the laser diode. This voltage (and hence current) is held constant
by the monitoringdiode and circuitry around the laser.(currentsource)
So, if this voltage is much higher than prescripted, you may assume
the laser is at the end of it's life, as the monitoring tries to get a certain
amount of laseremission by increasing the current.
Like I say, for this, you need the servicemanual.
So, dear Sir, is sometimes not that simple, but I hope I have given
at least some good advise. |
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