Micro Switch Found Short In Sony Car Stereo
MAKE AND MODEL: Sony Car Stereo Model CDX-GT44U
COMPLAINT REPORTED: None of the switches in the front panel work.
TROUBLESHOOTING AND RECTIFICATION DONE: Opened, dismantled the CD assembly and cleaned the set thoroughly. The design of this device was superb! Not strip wires! Dismantling was also very easy. Front panel, as we all might already know, can be slid out. Push the side locks and just slide the outer cover out through the rear side. Unscrew the top; remove the CD Unit after unscrewing from bottom. There you are, you can have a clear look of the inside. Unscrew the board from bottom. That’s all! You are ready for the trouble shooting.
Dismantled the front panel, by removing the PCB holding screws. Checked each micro switch for short and found Switch No.LSW911 short. This has a built-in LED. Though I tried giving a hard push inside to release the short, it did not work. So replacement was the only way. Checked with my friends for the original replacement and got one. Removed the SMD microswitch by hot air gun, adjusting the heat and air so as not to spoil the PCB or surrounding compounds. I also used a tin sheet after making a suitable opening in the middle which I placed on the switch before I used the hot air. This mask was to prevent the heat spoiling the display. Soldered the new micro switch. Placed the panel in its locking connector, applied power and found that all controls were working now. Unfortunately, the colour of the LED Micro Switch was blue instead of Red. A mistake done by my friend, who gave the part! Anyhow, I told the customer about this, and he did not mind it, which saved repeat of the removal which could have caused damage to the board.
Generally, I do not like the small Aluminium Electrolytic Capacitors used in such sets, as these have short lives. So checked the ESRs of a few and found that almost all of them were bad. So, wrote down the numbers of these capacitors and the value/voltage on a sheet of paper and rechecked to make sure that I did not make any mistakes. Plucked all the capacitors from the board using a player. (This is a delicate work, which needs some practice. The method is; hold the capacitor from the top, press it down gently and then shake it sideways not to rip off the tracks; not on the sides where these are soldered underneath. After a few shakes the capacitor will break away from its legs and come off easily.) Then replaced with ordinary capacitors and whenever the size was larger, I bent it down for proper seating. As these are to be mounted from the top, I cut the leads just enough for easy view to apply solder from the sides. Removed the tuner section, opened its case and replaced the cap in that too. After thoroughly cleaning the board, loaded the front panel, applied power and found that it was working very well! All the functions were also working. Placed the CD Unit on top and tried that too and found it to be working very well. I was relieved to see that the set was working very well in all respects. So, assembled the boards back and fixed the covers. Once again tried the set for several hours and it worked very well. Mission accomplished and intense satisfaction got added!
HERE ARE SOME PICTURES:
LINK FOR DOWNLOADING SERVICE MANUAL:
This article was prepared for you by Parasuraman Subramanian from India. He is 70 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
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