I have a JVC Tv Model AV27-bm4 that is 12 years old.Problem is no picture only line accross center.Has sound.Set worked fine before this happened.I don't have a schematic and am not familiar with what the different parts are or where they can be found on circuit board.I have tried to do some research and i think it may by the IC or IF.Can anyone please help.Repair shop wants between $80-$120 to repair,(does not pay).I can buy a new one for $188.
Hi there noch1
How much an hour do these guys, over there, earn an hour?
Your problem could be IC related but I doubt that although possible.
First, what experience have you of repairing electronic/electrical items? I mean are you aware of the dangers in looking at mains powered equipment? Are you aware for example to uplug a set when working on it and why? Do you know that there could still be dangerous voltages laying in wait for the unwary even in a set that is disconnected from the supply?
Secondly I would need a schematic of your set, if you have the relevant knowledge as well as the ability to solder and obtain parts.
Bernard
Hi noch1,
If we can find a manual then we may stand a chance. Are you familiar with television servicing at all?
What you are looking for is the vertical deflection output amplifier.....this is usually an IC mounted on a heatsink with five to nine legs. The problem is that there is also an audio amplifier IC mounted on a heatsink too.
The only way to distinguish between the two is that the output of one supplies the Defelection yoke which is on the tube neck and obviously the audio amplifier feeds the headphone socket if there is one and then to the loud speakers.
The chances are that you do not need to go that far, when servicing a television the first thing to look for is dry jointed legs on the IC (applies to both audio and vertical output IC's). Check for any components that either are scorch themselves or have scorched the board. These are possibly dry jointed.
What I mean by dry jointed is that there is no connection from the solder pad to the leg of the component....don't be fooled this can be a very fine black circular line around the leg of the component. Some are blatantly obvious, some are not. While you are there it is best to look over the whole board for dry joints especially the line output stage and the power supply. Inevitably when taking the board out of a set this sort of age then it may be the final straw that breaks the camels back and you can land up with another fault. In my experience more often than not you do! So it is best to get the soldering out of the way first.
right, next and most likely cause is that there is a large value electrolytic gone open circuit..can range between 470 to 1000uf around the 30 to 60 volt range. This is going to be mounted near the heatsink that is the vertical output stage. There are many ways of finding out if it is faulty or not but the first and most obvious is that it is going to look stressed ...I mean the covering is not going to look glossy, the top of the capcitor is bulged or there is evidence of the electrolyte leaking. I have had Panasonic sets where they have looked perfect but if you twist it lightly then one leg that is corroded breaks...asumming that it is a radial component...both legs coming out of the bottom of the capacitor. it does not take a lot of force to ruin the capacitor so do not over do it....compare it with a similar capacitor.if it is firm then it hasn't leaked.
You should have now found the fault...if not then the IC is probably faulty.
Remember if you are unsure about your ability to look in the back of the set then leave it for a qualified person. As you have told me there are still potentially dangerous if not lethal voltages inside a set even one that is unplugged from the mains. Even non lethal voltages can cause knee-jerk reactions that can cause you and the set serious injury and damage.
I do not recommend anyone goes into the back of a set unless they are fully aware of the potential hazards....even if you are then I will advise on a fault but I will not be held responsible for any injuries or damage incurred. YOU are SELF RESPONSIBLE in this matter.
Bernard