I own a 1992 Mitsu vs-4007r rear proj. tv with a problem i can't seem to fix. here it is: Turn it on. After couple of minutes, the volume goes completely off. This happens repeatedly. When i mount a VCR or game module to it and turn it on the volume stabilizes much longer, but then the volume goes "haywire" - can involuntarily increase and decrease. What do you suspect is the problem ? and in your opinion, is this tv worth reinvesting $'s to keep it running?
Most (all) electronics are soldered via wave soldering.
Picture a shallow pan full of liquid heated solder.... The components to be solder are installed on the board....the board with the leads hanging down off the components comes down and almost makes contact with the board... at this time the leads off the components touch the solder and the solder wicks UP, thereby soldering the components.
The problem comes with you have SMALL and LARGE items on the same board assembly... To solder a large item correctly, you have to use use more HEAT.... In most cases TOO much heat for the smaller components... If you decrease the heat so smaller components don't burn up during the process COLD solders are made in the larger items.
(Most mfg's DON'T go back over the board, hand soldering the "big" items... They fiqure it will last out of warranty, plus some so you'll buy more of their stuff...)
Over time (ON and OFF cycles) in which the board heats up, and cools off, the bad solders develop cracks, getting bigger and bigger... when they do that you develop a problem.
The "fix" is to resolder the board, looking for bad solders. (it could also be capicitors going bad, or that are bad. They dry out with age)
In your case it sounds like the audio board.
PS: POST back what the problem was, and the "fix" with pictures if you can.
BTW: You asked is it worth fixing? If you can fix it yourself (pull the board, then touch up a bad solder, then yes) If you have to pay someone, considering the age, How much longer the set will last, etc and what you can get these days, I'd think long and hard about sinking any money into it.
BTW: I would assume this is a common problem, so there may be some OLD TSB's (Techincal Service Bulletins) out there that note this problem with your set. The thing is this set is so old, it's for sure not "supported" in any way by the mfg... Good luck on finding "parts" if needed.
Best of luck to ya... but I think unless you can find the problem yourself, fix it, it would be to expensive to pay someone to fix the set.