JVC CRT TV repair. Model number AV-21TE.
This TV set came to my shop with a strange problem. Turn the TV set on, it works for a few seconds, then the timer led start flashing then I could see a vertical line across the screen then it shuts down. All this happens in less than five seconds.
Since I saw a vertical line before shutting down, here was my first step in repair. I opened the set and I could not see any signs of bad or burnt components. I went directly to the vertical IC LA7837 and started checking. All the capacitors in the vertical section showed high ESR reading and therefore, I changed all of them. I told myself, would that be enough to make the TV have a steady nice picture without shutting down. Well, I turned the TV on and guess what, it did not shut down but I still got the vertical line across the screen.
It is time to check the power reaching this IC. Well, there was 24 volts reaching this IC and that means only one thing- a bad vertical IC was found in that section and when I replaced it with a new one, the TV worked fine but for a short time. It started shutting down again but without the timer led flashing, just a normal shutting down.
I checked all the capacitors in the primary and the secondary section of the power supply with an ESR meter, and all the capacitors checked to be good. I checked the capacitors in the high voltage area and they all checked fine.
One thing came to mind, I got the magnifier lens out and started checking for bad soldering areas and guess what? There were lot of dry joints. The moment I re-soldered all these bad and cold soldering, the TV worked fine for more than two hours.
It was a lot of work and time but it was a time well spent. The joy of overcoming this problem was overwhelming and the experience that I gained from this was great.