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Philips Cdm4 19 Service 22


Philips Cdm4 19 Service 22




The Philips Cdm4 19 is a CD player mechanism that was used in many vintage CD players from Philips and other brands. It is known for its high-quality sound and reliable performance. However, like any other electronic device, it may need some service or repair over time. In this article, we will show you how to perform the laser current adjustment, which is one of the most common and important service procedures for the Philips Cdm4 19.


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What is the laser current adjustment?




The laser current adjustment is a process of fine-tuning the amount of current that flows through the laser diode in the optical pickup unit (OPU) of the CD player. The laser diode is the component that emits the infrared light that reads the data from the CD disc. The laser current affects the intensity and focus of the laser beam, which in turn affects the quality and accuracy of the data reading.


The laser current needs to be adjusted periodically because it may drift over time due to aging, temperature changes, dust accumulation, or mechanical shocks. If the laser current is too low, the laser beam may not be strong enough to read the disc, resulting in skipping, distortion, or no sound at all. If the laser current is too high, the laser beam may be too strong and damage the disc or the OPU itself, resulting in reduced lifespan or permanent failure.


How to perform the laser current adjustment?




To perform the laser current adjustment, you will need the following tools and equipment:



  • A Philips Cdm4 19 service manual. You can find it online at [1] or [2].



  • A digital multimeter (DMM) that can measure DC voltage and current.



  • A CD test disc that has a single track of 10 minutes of silence. You can use any CD that has such a track, or you can burn one yourself using a CD burner and a blank CD.



  • A Phillips screwdriver.



  • A small flat-head screwdriver.



  • A pair of tweezers.



  • A clean and static-free workbench.




Follow these steps to perform the laser current adjustment:



  • Unplug the power cord from the CD player and remove the cover by unscrewing the screws on the back and sides of the case.



  • Locate the OPU on the CDM4 19 mechanism. It is a black plastic box with a lens on top and a ribbon cable attached to it. It is mounted on a metal rail that allows it to move along the disc radius.



  • Remove the ribbon cable from the OPU by gently pulling it out from its connector. Be careful not to damage the pins or bend them.



  • Remove the OPU from the rail by unscrewing the two screws that hold it in place. Be careful not to drop or damage the OPU.



  • Place the OPU on your workbench and locate the trimmer potentiometer (pot) that controls the laser current. It is a small metal disc with a slot on top and three soldered pins on its side. It is usually marked with "VR1" or "Iop" on the OPU board. Refer to your service manual for more details.



  • Set your DMM to measure DC current and connect its probes to the two outer pins of the pot. The red probe should go to the pin that is connected to a large capacitor (C1) on the OPU board, and the black probe should go to the pin that is connected to a resistor (R1) on the OPU board. Refer to your service manual for more details.



  • Plug in your CD player and turn it on. Insert your CD test disc and press play. The disc should start spinning and you should see some current reading on your DMM.



  • Using your small flat-head screwdriver, gently turn the pot clockwise or counterclockwise until you get a current reading of 22 mA (plus or minus 2 mA) on your DMM. This is the optimal laser current for this model according to Philips specifications.



  • Press stop and eject your CD test disc. Turn off and unplug your CD player.



  • Reattach the ribbon cable to the OPU and mount it back on the rail. Screw it in place and make sure it is aligned properly.



  • Replace the cover and screw it back on. Plug in your power cord and test your CD player with some music CDs. You should notice improved sound quality and performance.




Conclusion




The laser current adjustment is a simple and effective way to service your Philips Cdm4 19 CD player mechanism. By following the steps above, you can restore the original sound quality and performance of your vintage CD player. However, this procedure should be done with caution and care, as any mistake or damage may result in permanent failure of the OPU or the CD player. If you are not confident or experienced enough to do this yourself, you may want to seek professional help or advice.


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