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

[J_Nichols]

It's a start.

If it were me, I would follow the mains cable into the power supply board in the TV (probably where the fuse is located). That board (likely a board with other functions as well) would have cables going elsewhere in the TV. disconnecting them and then observing whether the fuse blows (or not) would help you "trace" out what part(s) of the TV circuitry are defective. This is a very crude approach to trouble shooting but, who knows? It might work...

My guess is the problem is most likely within the power supply board itself.

I have done it after reading you and this time the fuse doesn't blows. So, the power supply is ok?

 

[MaxHeadRoom78]

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.
Max.

 

[J_Nichols]

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.
Max.

Ok, I try and I tell you what happens.

 

[cowboybob]

Ok, I try and I tell you what happens.

I've downloaded the schematic for your TV.

As Max suggested (with the mains disconnected), reconnect the plugs, one at a time, then reconnect the mains and see what happens to the fuse. Hopefully only one of the reconnected plugs will cause a blown fuse. Disconnect the mains between each, different plug reconnect. We're trying to isolate the problem board/circuit.

Follow the leads attached to that plug back to the board that is attached to. Take some in-focus pictures of the board to help us identify its function.

I should point out that actually finding the problem component(s) is going to be a bear. But, then again, no harm in trying.

 

[J_Nichols]

I've downloaded the schematic for your TV.

As Max suggested (with the mains disconnected), reconnect the plugs, one at a time, then reconnect the mains and see what happens to the fuse. Hopefully only one of the reconnected plugs will cause a blown fuse. Disconnect the mains between each, different plug reconnect. We're trying to isolate the problem board/circuit.

Follow the leads attached to that plug back to the board that is attached to. Take some in-focus pictures of the board to help us identify its function.

I should point out that actually finding the problem component(s) is going to be a bear. But, then again, no harm in trying.

Of course, I understand the mechanism to correctly find the problem. Connect cable, connect mains and see what happens, then disconnect the mains, disconnect the cable and try with another one.

I will try that tomorrow.

 

[cowboybob]

... Of course, I understand the mechanism to correctly find the problem. Connect cable, connect mains and see what happens, then disconnect the mains, disconnect the cable and try with another one. ...

That is correct.

 

[Willen]

I have found the fuse was broken. I have replaced it and when I connected it, the fuse has been broken again with a big spark.

Going back: Same had happened to my computer power supply. I found just a diode shorted. I replaced and fixed the supply.

 

[J_Nichols]

That is correct.

Found the cable that is causing the problem

 

[J_Nichols]

Going back: Same had happened to my computer power supply. I found just a diode shorted. I replaced and fixed the supply.

Well, I have follow the advices from people of this thread and the first thing I have done is to disconnect all the wires from P.S to the main board. Then, connect 1, switch on the TV and see if something happens. Disconnect the TV, disconnect the wire and try with the next one until one has caused the fuse to break.

I think that if the problem would be in the diodes the fuse would has broke at the first try with the first cable, not?

 

[Willen]

Sure, if there's no problem just with Power supply, then as others saying, problem is in other sections.

 

[J_Nichols]

Sure, if there's no problem just with Power supply, then as others saying, problem is in other sections.

Yes, it seems that the problem is in other section.
The question now is what to check and how to check it.

 

[cowboybob]

Found the cable that is causing the problem...

OK.

In this pic:

you say that the cable goes to the white item (red arrow) where the yellow paper is attached.
Is it the wire that the black arrow is pointing at? And does that wire continue to where the blue pointer indicates? Is there a connector at that point?

Is that the cable you disconnect and the PS short disappears?

 

[J_Nichols]

OK.

In this pic:
View attachment 96288
you say that the cable goes to the white item (red arrow) where the yellow paper is attached.
Is it the wire that the black arrow is pointing at? And does that wire continue to where the blue pointer indicates? Is there a connector at that point?

Is that the cable you disconnect and the PS short disappears?

Yes, it's the cable with the yellow paper attached.
It continues where black arrow is pointing at.
It's connected in the P.S. board near a component that I don't know. (transformer?)
So all you have said about the color arrows is true.

The wire starts/end, depending from which angle you place the starting point, in the P.S. board and it's not with a connector. If you want to disconnect it from the board you have to use a desoldering tool.

 

[J_Nichols]

The unknow component is like a small metallic box and the color is dark red. It has the number 40 46.

 

[cowboybob]

Where, exactly, is the PS relative to the brown wire? Is the dark red metallic box visible in the video?

Is the fuse still blowing with everything that can be disconnected from the PS??

 

[J_Nichols]

Where, exactly, is the PS relative to the brown wire? Is the dark red metallic box visible in the video?

Is the fuse still blowing with everything that can be disconnected from the PS??

The dark red metallic box in very little visible in the video. Tomorrow I can take some clear pictures of it.
When I disconnect every cable that goes from P.S. to the main board it's ok to switch on the TV because the fuse doesn't blows. If I connect a different cable the fuse doesn't blows. It blows when I connect the cable I have just told you.
I don't know if that is exactly the question you're asking to me.

The brown and black wire are parallel to the P.S. board. If you would be watching TV the brown wire would be at the left side.

 

[cowboybob]

Please bear with me, J_Nichols. I am still unclear which cable you are referring to that, when disconnected, allows you power up the TV without blowing the fuse.

Is it this this one (the wide ribbon cable that seems to go to the main board)?:

 

[J_Nichols]

Please bear with me, J_Nichols. I am still unclear which cable you are referring to that, when disconnected, allows you power up the TV without blowing the fuse.

Is it this this one (the wide ribbon cable that seems to go to the main board)?:
View attachment 96292

I think the best way is to take some pictures and post them here.

About the cable, I mean that when I connect only the brown/black cable from the P.S. to the main board and I turn on the TV, the fuse blows. If I do the same, but instead using the brown/black cable I use other one (just one cable connected from the P.S. to the main board and the rest cables that go from the P.S. to the main board disconnected) the problem doesn't happens.

The ribbon one no. It's the one you marked with arrows in the above picture.

 

[J_Nichols]

More detailed picture, including what cable I am refering to (right picture) and the red component that the cable is connected to, in the P.S. board (left picture).

 

[cowboybob]

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.