Stuck In Standby Problem Solved In PANASONIC 5.1 DVD Home Theater System-SB-WA340&SA-HT850
This system was brought to me by a close techie friend of mine, after making futile attempts to resolve the complaint captioned above. The mains input and power supply and final Amp were housed inside the Active Subwoofer Box with an inter connecting cable to the DVD player, which carried the power in, standby release signal out and audio out. After dismantling the boards and checking for any dry solder or visible damages of components I restored the boards and all the inter connecting flexible strips and connectors as these were found strained and the blue colour insert assists of some of which were found either loose or lying outside.
Then checked the push to on switch and found it to be ok as that path was pulled down when the switch was pressed to trigger the release from standby. As I could manage to download the service manual of the DVD player and Sub-woofer, trouble shooting was quite easy. Following are the links: https://www.manualslib.com/manual/3153684/Panasonic-Sb-Wa340.html
https://elektrotanya.com/panasonic_sa_ht850_gc.pdf/download.html
But this mood was spoiled by yet another issue relating to removal of the PS-Amp unit from the Sub-woofer. Though I removed the two top screws at the rear of the unit and the screws underneath, upon which the speaker grill side came off, the slide-in-slide-out unit, did not budge even a centimeter in spite of even trying to pull out with players. Then I hammered the metal cover of the unit through whatever slots and holes I could find using a flat tipped heavy screw driver, after which it just slid out a few centimeters. Let us have look at the pictures to follow:
My manual efforts of hammering at all sides with equal progress slid out the unit little by little and finally the unit came out sufficiently well. It took well over three to four hours of hard labor. Unfortunately, I never had anyone just to hold the outer case, which certainly would have eased the efforts. My hands, shoulders and connected parts of the body started aching out of fatigue! My wife started screaming at me enquiring about the unusual thudding noise coming from my service room, which was hindering her TV entertainment! She asked me whether I was doing electronic servicing or carpentry-Masonry-Ironsmith work! She was so annoyed that she asked me to return the unit to the customer, without knowing that it was my close techie friend at the other end! (LOL) Then she asked me to go to the garage outside and continue, which I declined as for doing this type of work, we need to sit on a chair, keeping the unit at a table level.
Anyhow, after continuing the hammering which fetched some more murmuring curses, I could manage to slide it out by shaking the unit to all four sides. Now let us look at the reason for the obstinacy of this unit to come out:
Evidently, the bottom portion had rusted and got stuck with the hardboard bottom of the unit, which prevented sliding movement. Anyhow, by the time I took out the unit, I was dead tired and opted to take a break and continued the work only next day. Looking at the circuit diagram, I located the relay on/off control transistors and checked for any defect. I could not find any. But there were dry solders, which I patched up well. The connectors had fungi formation, which I cleaned using IPA. After this, when I applied power, the standby got released and the DVD showed signs of waking up. I noticed that the tray open/close was not proper. So, removed the mechanism, cleaned the driving belt and put it back.
But, even though the mechanism started working and detected loading of CDs, it never played any of the DVDs/CDs. I even tried cleaning up the lens a couple of times using IPA. But it did not show any improvement. Anyhow, as the user did not want to use it and was only keen in using the Amp to play from the TV and other sound inputs in the house, I checked the Audio In function and found it to be working on all the four speakers and the subwoofer. I spent another hour or more to scrape the stuck hardboard and clean the bottom of the PS-AMP Unit so that it slid in smoothly. So, conclusion was arrived at this stage and sets closed for return to the customer. Following are supporting pictures:
Anyhow, mission got accomplished without much complicated electronic problems solved. So, satisfaction had every reason to seek entry into the collection bag, and it was granted!
This article was prepared for you by Parasuraman Subramanian from India. He is 76 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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