Greetings all, new to the group.

Having some problems with my TV listed above. Minor issue that does not justify going on and buying a new TV. What it was doing was, when first turned on for the day or after a couple of hours, I would lose sound and picture, but the power LED would still be on. I had to turn the TV off and on 5-7 times for the picture and sound not to cut out.

I did a ton of research on this, and (I can provide links if needed) it seemed as though the horizontal drive circuitry was bad. There apparently was a Horizontal drive kit from Philips for the L01.1U chassis that replaced the following components (which I replaced):

1-BU4508DX (Transistor)

1-BC547 (Transistor)

1-BC557 (Transistor)

1-47m/50v (Capacitor)

1-220m/35v (Capacitor)

I also replaced the BC33725 and BC32725 transistors since there was a burn mark at these points, and further tests on a transistor tester showed they were bad. So I sealed it up a couple of days ago and I thought I was good to go. But when I went to turn on the TV this morning, same issue, but I only had to turn it off and on once, not 5-7 times before the repair. This happened twice so far today.

I checked the service manual, and the error code told me to check for black current loop protection (device TDA6107/8, and items 7330, RCB amps, and the CRT). I can provide the service manual if needed.

Now, I know how to do circuit board repair, and probe needed points if someone tells me what to test, but this is my first TV repair. Any suggestions would be welcome.

Thanks!

Most likely the CRT is getting a bit weak. these units shut down when AKB (auto kinescope bias) is not satisfied. Generally you can get more life out of it by increasing the G2 voltage, which is controlled by a pot on the flyback. The bottom one, the top one is focus.

Turn it up to where it will stay on, but not too much. Darken the room and set it so there is no "slick screen" under the video, lower the brightness and contrast (or "picture). set it right to the edge, and then lower it just a hair.

Something is in error here. When there is a fault in the horizontal drive, usually the horizontal output will fail, being shorted. This will sometimes cause a power supply failure that makes the set too expensive to repair. this is what the engineers were after of course, keeps them in a job. That's why they won't even let the set run if the CRT gets a little weak. Sony did the same ****, but they didn't all shut down, they just never produced a picture. Later models did shut down if any of the guns in the CRT got weak. This was how they sold TVs.

So, something was amiss. you did not check the transistors with a meter ? Waht kind of transistor checker is it ?

Thanks for the reply. I don't know what brand of transistor checker it was (at my school's shop). I'll have to get that information on that and re-post. Basically, you stuck the transistor in and there was a LED indicator to tell you it was good when lit. It would check NPN, PNP, etc. But the circuitry had to be our of the board for me to check it. I can check the levels on the board components (I have a multimeter if that helps), but just let me know what I need to check and I can do that and post back if needed. This post will probably grow since I am a novice, but I am willing to learn but I want to take me time and get it right too. Thanks for your patience thus far.

Now, since I am new to TVs, I know you are referencing the flyback transformer. So, to get this straight I have to look for a potentiometer (perhaps with a flat head dial) around the bottom of the flyback assembly on the main board? The top pot would be on the CRT itself?

I'll wait for your response until I try something different. Like I said I want to take me time and get this right. Let me know if you have any questions.

Thanks!

In article ,
says...

Most likely the CRT is getting a bit weak. these units shut down when AKB (auto kinescope bias) is not satisfied. Generally you can get more life out of it by increasing the G2 voltage, which is controlled by a pot on the flyback. The bottom one, the top one is focus.

Turn it up to where it will stay on, but not too much. Darken the room and set it so there is no "slick screen" under the video, lower the brightness and contrast (or "picture). set it right to the edge, and then lower it just a hair.

Something is in error here. When there is a fault in the horizontal drive, usually the horizontal output will fail, being shorted. This will sometimes cause a power supply failure that makes the set too expensive to repair. this is what the engineers were after of course, keeps them in a job. That's why they won't even let the set run if the CRT gets a little weak. Sony did the same ****, but they didn't all shut down, they just never produced a picture. Later models
did shut down if any of the guns in the CRT got weak. This was how they sold TVs.

So, something was amiss. you did not check the transistors with a meter ? Waht kind of transistor checker is it ?

A good TV service tech never left the shop with out a
buck boost filament transformer!

Jamie

Jamie,

Thanks for the comment - could that help?

The fly has two controls on it usually. the top on is focus and the bottom one is G2, or "screen" voltage. That refers to an element of the electron gun in the tube. the voltage required on that element varies from tube to tube, as much as from 100 volts to a thousand. It all depends. Your unit probably runs at about 400-600 volts.

Nopraslly in that type of unit, the CRT gets weak, and since you keep restarting it, the cathode's heat is higher, and eventually wil warm up fast enough o that the microprocessor in the TV will not shut it down.

To cause the sale of another new TV, which they just happen to build.

On those models, look at the picture whiile increasing the G2/screeen control. When you see it start looking like a good picture rather than a cartoon, you are getting there. the trick is to not go too far.

I have not ofund a way to defeat this shutdown if the CRT bias cannot bring it within close enough so it does not shut down. Nobody would pay me to do it because they are not worth all that much.

At the shop, I would not put more than thirty minutes into diagnosing that. Even if I did, any major part and 90 % of the time it is junked when you ge the estimate.

But this is SER, and that means repair. SOmetimes is matters not is it is economically logical. Soe people want some experirence. Some people want their old **** from highschool to work again, like that old Marantz and ****. OH YEAH.

The TV you got is not vintage. Really, it is not worth fixing at all. But the thing is is you are not here for a sales pitvch for new TVs. You want to gian knowledge.

Cool. I will help. So take and turn that G2 control up, the bottom one ont eh flybacks, exactly 12 degrees. I mean get a protractor. Do it while the set is off even. I will bet you will see a lot better picture and it will stop shutting down on you.

Now, if you want to learn more...

"A good TV service tech never left the shop with out a
buck boost filament transformer! "

We made the roadf guysd sput them in the "tube caddilac".

Tube caddy, get it ?

Thanks and sorry for the late reply. To answer your question from the first post, the transistor checker I used was a BK Precision model 510 transistor tester.

So, about the G2 voltage - take it it's a potentiometer - can I take and post pictures to make sure of what it is?

Thanks again!


On Monday, August 11, 2014 3:15:57 AM UTC-4, wrote:
The fly has two controls on it usually. the top on is focus and the bottom one is G2, or "screen" voltage. That refers to an element of the electron gun in the tube. the voltage required on that element varies from tube to tube, as much as from 100 volts to a thousand. It all depends. Your unit probably runs at about 400-600 volts.



Nopraslly in that type of unit, the CRT gets weak, and since you keep restarting it, the cathode's heat is higher, and eventually wil warm up fast enough o that the microprocessor in the TV will not shut it down.



To cause the sale of another new TV, which they just happen to build.



On those models, look at the picture whiile increasing the G2/screeen control. When you see it start looking like a good picture rather than a cartoon, you are getting there. the trick is to not go too far.



I have not ofund a way to defeat this shutdown if the CRT bias cannot bring it within close enough so it does not shut down. Nobody would pay me to do it because they are not worth all that much.



At the shop, I would not put more than thirty minutes into diagnosing that. Even if I did, any major part and 90 % of the time it is junked when you ge the estimate.



But this is SER, and that means repair. SOmetimes is matters not is it is economically logical. Soe people want some experirence. Some people want their old **** from highschool to work again, like that old Marantz and ****.. OH YEAH.



The TV you got is not vintage. Really, it is not worth fixing at all. But the thing is is you are not here for a sales pitvch for new TVs. You want to gian knowledge.



Cool. I will help. So take and turn that G2 control up, the bottom one ont eh flybacks, exactly 12 degrees. I mean get a protractor. Do it while the set is off even. I will bet you will see a lot better picture and it will stop shutting down on you.



Now, if you want to learn more...