Question about Denon DHT500SD System
How do I clean the optical pickup assembly lens?
Manually cleaning the lens
To locate the laser lens, look around the door or drawer of the DVD player and you will see a small circular disc, which is often called the turntable or disc platter. Right off the edge of the platter you should see a small clear lens. There are some manufacturers that have had problems with the lens, depending on the age of the unit. In these problem players, moving the unit to a different location, turning the unit upside down, or sometimes even without moving the unit, the lens can become detached from the laser assembly and floats around inside the unit. You can re-glue it back with a little crazy glue, BUT it must be perfectly centered, and without getting any glue on it. So, if you don’t see the plastic lens, but instead see the laser pick-up assembly, look around for the lens inside the unit and glue it back on.
To clean the lens you must use very little pressure. Take a cotton swab and barely moisten it with plain, non-scented, or oily type alcohol. In a swirling motion, very gently rub the lens until you’ve covered it entirely. Then repeat using the dry end.
If the cleaning didn’t help, don’t despair just yet. You can see if there’s a problem elsewhere in the unit by using a few simple tricks and tips.
First thing you want to see if the unit’s laser is in good working order. This method isn’t foolproof, but most of the time works admirably. When you insert a disc, see if you can look up underneath where the disc sits on the turntable. Observe the laser lens going up and down. If the lens is trying to focus, that’s good! After a few seconds of the lens trying to focus, the platter should start to spin. On almost every CD/DVD unit I've encountered, the unit won't spin unless the laser has properly focused on the surface of the disc. If the unit spins up and and then shuts down, you should check and make sure the laser pick-up assembly slider mechanism is working without any obstructions and that the small chrome rail that it slides on is slightly greased. Don’t go overboard with the grease though, as too much can cause all sorts of problems.
The slider mechanism, depending on the age of the unit and the manufacturer, consists of the small chrome rail, a drive motor, a small gear assembly, and (in some units) a small belt that drives the slider unit via the motor. This small belt causes all sorts of problems. If the belt is broken or slipping, it can cause skipping, dropouts, or simply no start up at all. Also, if the belt breaks in the middle of the disc, the drive mechanism gets hair or dirt wrapped up into the gears, or the pick-up assembly doesn’t return to the start position (called home), the unit will (99% of the time) refuse to release the disc, causing it to become stuck inside the unit. There’s a little micro or leaf type switch located at home position that sometimes gets dirty or breaks and, causing this problem also.
If the disc starts to spin slowly and doesn’t come up to speed, the spindle motor that’s attached to the turntable platter is a common problem. There could also be a problem with the spindle motor driver controller IC or the power supply regulator that supplies voltage to the driver IC. If the disc starts to spin and then spins really fast, or stops and starts to spin backwards, your problem is the laser pick-up assembly or the servo control circuit. If you continue to have problems after cleaning and checking the other things listed above, you may have a problem with the player's alignment. Of course, one of the problems you'll face checking alignments on a DVD/CD player is that you’re going to need to use an oscilloscope on most of them. If you have the proper tools and equipment, the first thing to look at is the RF pattern of the unit while its playing. It should be a sharp and clear pattern. If it's dull and smeared, then the laser could be weak.
Also, in these units are very critical alignments called the focus/tracking gains and offsets. When these alignments are off, it can often cause intermittent troubles. As the unit ages and parts change value, so do these alignments, and will need to be checked. In my time as service technician repairing DVD/CD players, 65% of the laser pick-up assembles I have tested were good and only needed a small adjustment. Today's technology makes it unfeasible for a shop to hook up a DVD/CD player, and even some recorders, to their equipment and make these adjustments because of the cost involved.
hope this may help;
DON'T FORGET TO RATE;
Posted on Jan 11, 2009
Open the cover of your dvd player,then get your hair dryer and turn on the hair dryer and clean module board.after that get some 1pc of cotton buds try to clean gently the lens 3 to 5 times.then returned the cover .and turn the unit.
i hope it will work.
Posted on Jan 11, 2009
You use a Lens Cleaner such as those advertised on this eBay link:
Hope this helps
Posted on Jan 11, 2009
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Posted on Jan 02, 2017
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