When plugged in a relay switches, a few seconds later a loud garbage noise comes out of the speakers for a second or 2 another relay switches and it shuts itself off. No fuses are blown and nothing obvious on the boards. I took out the main fuse and put a light across it. It comes on, goes off, comes on goes off continuously. Is that normal? Don't have a schematic and I am not familier with this TV. Can anyone help?
If the light goes on and off, there is a short somewhere in the set, as that would be the power supply switching on and off, trying to start up. it could be the Horizontal output transistor is shorted, the regulator bad in the power supply, the sweep power supply has a short like a bad capacitor or diode. Without a service manual, and checking the circuit, its purly a shot in the dark my friend. If you have no solid state training on printed circuit board, play it safe and consult a pro in this matter, as there is no quick fix or easy card to replace in this set. There are no real user replaceable parts in this TV set. Good Luck, and let us know how you made out with this repair.
Thanks for the reply Larry
I think I needed a refresher in 101. I went through most everything but for some reason skipped the Horizontal output trans. I haven't worked on TV's in a long time because I was working for a major chip manufacturer (almost 20 years doing the maintenance & repairs on there equipment) and didn't have the time. But now I am on my own and doing whatever it takes to support the family & pay the bills. I've worked on electronic equipment for over 20 years and know the dangers inside of TV's. But electronics is a good part of my back ground and I have at least 5 other TV's to tackle along with all the other jobs I have going on. So off I go into TV land.
I pulled the Trans. and put the light bulb on it (across the open fuse) to see how it would react now. It comes on and dims out slowly. This was done on the bench and the board not put back into the TV. I would think that is the way it should work. Meaning there don't seem to be any other direct shorts,,,correct? Is there a way to jumper the high voltage section out of the way so I can check out the other portions of the TV and not have to deal with that section until I'm ready to check it out? Also is there any other parts that commonly go out when the Horizontal output does? The diodes and caps connected to it all seem to be OK. Any help is greatly appreciated.
Measure the transistor, and if it is shorted put a new one in with the light bulb and this will tell you if the flyback is also bad. Thats exactly what the light bulb is suppose to do when there are no other shorts. learned that trick along time ago from an old time radio guy. I have used that even still today to prevent new parts from grtting shorted out.
Well that was fun but no cigar just yet.
The Trans was shorted so I put another one in and tested it with the light.
The light came on very dim, then dimmed away until gone and stayed off. So I put the board in the TV and hooked it all back up. Turned it on and nothing seemed to have changed. So I thought the trans got shorted again and put the light on it. It started going on & off again. Something in my head didn't make since so I tried a few things before giving up. When I pulled the board off of the back of the yoke and tested it, the light dimmed again. Is that telling me that the tube is shorted? Everything else was hooked up. But the TV seemed to do the same thing as it did when I first tried it. It still ended up shutting itself down again. This TV has 3 fusable resistors in it around the flyback. 2 - 1/4 watt and 1 - 3 watt - all small in value. I think I am going to lift one end of the 3 watt and see what that does. I'm hoping it will try to show if there is another problem elsewhere. Also the sweep section is located on a plug in board (I believe it is the sweep section) and does make a little difference when not in the circuit.
Any thoughts of what to try?
You most likly have a bad flyback transformer from what you have been describing, but I do still have to give you alot of credit , as your not moving a head of your self with out asking for direction as well as advice. My friend, at this junction, I would advise a service manual will be needed to complete this diagnostic. If you have one please forward to [email protected].