CD Player Laser Diode Replacement

Lasers fail in a strange way. When my Marantz laser was about to go, the sound became fuzzy and noisy. This is due to the laser becoming weak. It also became very choosy as to which brands of CDs it would play and which it would not. In addition, there was a random "NO DISC" error.

Although removing the flexi-circuit was not necessary, I was curious to see the laser design and construction. Since the old one was non-operational, I decided to desolder it.

A metal plate covered the laser diode and the focusing assembly, so the next step was to remove the plate.

As you can see, the laser assembly is within the black plastic tube construction. The focusing platform and its mechanism take up most of the space. The focusing lens sits above the prism; however, you cannot see it from this side.

The laser diode is within the black plastic construction that looks like the Soyuz TMA module. At one end, there is a prism to deflect the laser beam downwards where the CD would be.

This is the image after removing the lens focusing assembly. You can see that part on the CD Player Laser Lens Assembly page.

The laser diode and the phototransistor are on the PCB on the RHS. The laser shoots a beam of light towards the prism on the LHS.

I decided to open this part to have a look at the laser diode and phototransistor components.

As you can see, a laser beam shoots from the diode towards the prism, which deflects the beam at 90-degrees towards the CD. The reflected beam from the CD takes a slightly different path, and shoots back towards the prism. The prism deflects this reflected beam back into the laser diode where a phototransistor detects it. This whole process happens many times a second whilst the CD is spinning.

As you can see here, I have removed the laser diode PCB, and it is just a darkened plastic tube.

Here is the laser diode. It is 1AL2PT tube diode with multi pins. CD lasers are typically AIGaAs semiconductor material with a wavelength of 780 nm. Click the image above for an enlarged view.

From the circular pinout arrangement, it appears to be a tube laser diode with multi-pins soldered to the flexi-PCB.

This particular component contains dual laser diodes, including their phototransistors for sensing the reflected laser beams. It is all self-contained in a multi-pin package. Unfortunately, I was not able to find much information about it; otherwise, I would have had a go at replacing it just to see if it worked. This diode has 1AL2PT written on it. If you are working for the factory then please feel free to send me any information about this component.

Laser diodes are particularly prone to static electricity damage, so if you are able to buy a replacement diode, then ESD precautions are vital. If you are changing the optical pickup, then you should still take ESD precautions as this assembly has a circuit on the flex cable.

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