My TV doesn't turn on. How to repair it?

[J_Nichols]

Ok. Thanks for the clarification.

I can see now that the brown (blackish) wire appears to go to the Horizontal board (with the fly back transformer). I can envision that board being the problem. that circuit is by far the most power (current) hungry and with the highest voltages floating around. Not unusual for a component to be overloaded and fail to a shorted condition. AND take out other components in the process.

A portion on the PS schematic:

The three red arrows on the right feed the Horizontal Board, HV (24.5kV), Focus and Screen grid elements of the CRT and represent a significant load on the PS. Of course, the problem may also lie in the feeder circuit(s) of the PS.

In all honesty, it is going to be difficult (at best) to trace, let alone troubleshoot, where the problem is.

I should note that the manufacturer assumed that field repairs would be handled by Board Level replacement.

Thank you very much for the time and information you are bringing.
It will be difficult, as you say, to repair it.
But one question... I have seen in one youtube video that the problem could be caused by the PTC, and replacing it with a new one could solve the problem. I ask you that because I have seen that the brown black cable is very near of the PTC. What do you think?

 

[cowboybob]

Thank you very much for the time and information you are bringing.
It will be difficult, as you say, to repair it.
But one question... I have seen in one youtube video that the problem could be caused by the PTC, and replacing it with a new one could solve the problem. I ask you that because I have seen that the brown black cable is very near of the PTC. What do you think?

A PTC ( Positive Temperature Coefficient fuse), ordinarily, reacts to an over-current event with an exponential increase in resistance (due to an increase in temperature), effectively removing a path for the current (a "sort of" open). When power is removed, the PTC cools and a low resistance path is restored: a self healing fuse.

In your case, there is a "hard" short somewhere in the circuit(s) that is blowing the mains fuse. It could be more than one.

Can you read schematics?

 

[J_Nichols]

A PTC ( Positive Temperature Coefficient fuse), ordinarily, reacts to an over-current event with an exponential increase in resistance (due to an increase in temperature), effectively removing a path for the current (a "sort of" open). When power is removed, the PTC cools and a low resistance path is restored: a self healing fuse.

In your case, there is a "hard" short somewhere in the circuit(s) that is blowing the mains fuse. It could be more than one.

Can you read schematics?

I think I understand. I have tried to read the schematic you have shown in the last post and of course, now I see the variable resistor is the PTC. It's not easy for me to read a schematic.

So you mean the problem can be in more than one place at the same time as you wrote in the last post.
I think it won't be easy to repair, because my electronics knowledge is very basic. You have suggested to replace the board with a new one in the last post, right? but that TV has more than 20 years so I think it won't be possible to buy a new one because the maker stopped selling it a long time ago.

 

[cowboybob]

So you mean the problem can be in more than one place at the same time as you wrote in the last post.

I'm afraid that's a distinct possibility. Might end up chasing the problem(s) all over the place.

I might encourage you, though, to continue your pursuit of an electronics learning curve. Start with something a little less complex and come back to ETO for any help you might need.

 

[J_Nichols]

I'm afraid that's a distinct possibility. Might end up chasing the problem(s) all over the place.

I might encourage you, though, to continue your pursuit of an electronics learning curve. Start with something a little less complex and come back to ETO for any help you might need.

I think the problem is very complex to repair it. Tomorrow I will put the TV in the rubbish. Before that, I will get some pieces from the TV.

Thank you very much for all your support.

 

[cowboybob]

You're welcome.

 

[J_Nichols]

You're welcome.

Thank you. You've wrote a lot of valuable information, but I think it's complex to repair. It will be more complex to repair with my technical skills (almost zero). If I pay to a technician to repair it, it will cost more than a new second hand one.

So there are only a few options.

 

[vietchiase]

Then it would appear the problem is in another section, if the PS board has various plugs for the different supplies then try inserting them one-at-a-time.
Areas most likely are the Horizontal output section and the vert out, also audio output could cause it.

 

[cowboybob]

Welcome to ETO, vietchiase!

Looking forward to your contributions .