Know the safety facts first

If you have no electronic experience or training, there really are no user serviceable parts inside the set. It's all solid state, and you’re going to need to know how to use a simple digital or analog multi-meter. Also, you should know how to solder, as well as unsolder, as almost all of the parts in most sets are soldered in place on the printed circuit board. When dealing with TV/DVD combos, there are also the safety issues concerning the HI Voltage found in TV sets. All TVs with a picture tube, including three tube projection sets, will have a HI Voltage transformer with a heavy red wire that runs up and connects to the picture tube with a suction cup. Under there is an average of 32,000 volts when the sets on, and even when the set is off, can hold a large electrical charge.

First things to check

The most important thing for a DVD/CD player is make sure the unit’s laser lens, or what some call the “eye”, is clean and free from any film or dirt. The best way to do this is to use a readily available, CD/DVD lens cleaning disc. I have found that 65% of people with a "broken" player could have saved themselves a trip to the repair shop if they would have used a cleaning disc. Of course, sometimes a cleaning disc can be hit or miss, as there are some players/recorders that won’t allow cleaning discs to work inside them. If this is so, or if the disc cleaner doesn’t work, there’s another step that involves taking the unit apart.

Getting into the unit

For this example, the unit is a TV/DVD combo. You just need to remember the safety facts mentioned above about working inside of a TV set, and IF you ever feel uncomfortable at any step of the way, STOP! Reassemble the unit and take it to a repair shop.

Lay down the TV combo unit face down on a soft surface. There should be screws holding down the back to the set. Remember to look around the back area around where the inputs are for any fasteners. Gently pull the back straight up, remembering that sometimes you may need to tap around the cabinet to loosen the back from the front cabinet.

Once the back has been removed, look around the bottom part of the chassis. Depending on the make and manufacturer, most DVD and VCR chassis are mounted on the bottom of the set. Examine the bottom of the set while it's lying down to see if there are any screws holding onto, or holding in, the DVD chassis assembly. Also, look all the way from the back toward the front to see if there are any screws holding in the chassis from the front of the unit. Be sure to check for wires and cables that may be attached to the DVD chassis and TV/power supply, as they will have wire ties on them. Sometimes these have to be clipped off, BUT always remember to tie them back out of the way when you’re ready to reassemble.

Once the DVD chassis is loose, sit the TV up so that it rests in a normal position. However, some sets cannot stand up when disassembled and will break the bottom of the cabinet if you try. So, if the cables are not long enough to slide the DVD chassis out, you're going to need someone to hold up the set until you can slide a block of wood inside the cabinet from the top to the bottom of the cabinet.

Gently slide out the DVD chassis, and make sure you’re not stretching any ribbon cables or wires. Some manufacturers will have a metal cover over the DVD chassis assembly, which is usually held on by two or four screws. Take the screws out and slide off the cover by lifting straight up, or slightly lifting the back part of the cover and sliding back while pulling at a slight angle. This is also how to remove most covers on regular DVD/CD players/recorders.

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.

Now, if no cables are disconnected, and if you can verify nothing is touching the TV or DVD chassis, you can plug in the unit and check if this helped the player to "see" again. Most of the time you can check as is, though on the combo units you're going to have to slide the chassis assembly all the way back into the cabinet to get it to work because the cables are often too short. If this didn’t fix the problem, please read on.

Other things to check

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.

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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.

Also, in a DVD/CD player there are many complaints where the disc gets stuck inside of the unit. This could be as described earlier, but there’s also what’s called a drawer/disc tray opener and closer mechanism to contend with. On many models, old and new alike, there’s a small belt that goes bad and wont let the tray open. You can usually put your ear very close to the front of the unit and, if this is happening, hear the motor spinning when you press the eject button. Another cause is the nylon gears, which can get jammed up with dirt and dust. Also, in other cases, you could have a motor problem, or the driver IC could be at fault. If you suspect that the motor is at fault, simply measure the voltage on the tray motor while pressing on the eject button. If the voltage comes up between 6 to 12 volts, depending on the manufacturer, then the motor needs to be replaced.

Alignments

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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.

Wrapping it up

If you tried to clean the lens, make sure the unit was trying to spin, and verified the slider is working, there’s not a lot more that a consumer or end user can do. It’s going to be up to you to assess the value of the unit, and compare it to the cost of a new one or the estimated cost of the repair. Hopefully you'll be able to make a better decision based on your findings. If you did make any improvements to the unit and fixed a problem, GOOD FOR YOU!

As a final step, you must follow the directions in reverse for the assembly of the combo unit. Please remember to tie up any cables or wires that you took loose. Garbage bag ties do the job nicely, BUT if they're the metal, paper wrapped types, keep them away from the HI Voltage lead and circuit board parts inside the set. Remember to remove the wood block if you used one, and please be careful not to hit the picture tube neck when reinstalling the back of the set. Don't forget to put all the correct screws and fasteners in the correct place, as they are put there for a reason!.

Most importantly, always remember safety when working on anything electronic or mechanical.

Good Luck!

by Larry Dillon

Edited by Matt Whitlock

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