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

[J_Nichols]

I have an old CRT tv and when I try to turn on I press the button, but nothing happens.
What could be broken? Should I start checking the fuse?

 

[cowboybob]

I am not being glib when I ask; "is it plugged in"?

If it is, then how comfortable are you working with electronics where significant, lethal voltages are present?

 

[alec_t]

Welcome to ETO!
I hate to be the bearer of bad news, but if the fuse is ok and mains power is getting to the set then, given the questions you are asking, it is clear you don't have the skill set needed to fix the TV safely.

 

[JimB]

What could be broken?

The switch ?

JimB

 

[J_Nichols]

I am not being glib when I ask; "is it plugged in"?

If it is, then how comfortable are you working with electronics where significant, lethal voltages are present?

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.

Well, working with high voltages I am not very comfortable. But I ask everything before testing it.

 

[J_Nichols]

Welcome to ETO!
I hate to be the bearer of bad news, but if the fuse is ok and mains power is getting to the set then, given the questions you are asking, it is clear you don't have the skill set needed to fix the TV safely.

The fuse was broken and I have replaced it with a new one and there is some damage because the new fuse has been broken again.

 

[cowboybob]

Could you provide the Year, Make (brand name) and Model of the TV? Photos (inside and out) would be useful as well.

A schematic (wiring diagram) would be very useful to us.

 

[J_Nichols]

Could you provide the Year, Make (brand name) and Model of the TV? Photos (inside and out) would be useful as well.

A schematic (wiring diagram) would be very useful to us.

It's an ITT Nokia, 3722 OS ideal color.
The year I think it's around the end of the 1980's or beginning of the 1990's

I will take some photos. Where do I get a schematic?

 

[J_Nichols]

Not mine, but it's exactly the same
**broken link removed**

 

[Nigel Goodwin]

Chuck it in a skip! - it's completely worthless, you can get FAR better working CRT sets for nothing (as no one wants them).

 

[MikeMl]

I second the "not-worth-fixing" suggestion. If I tried to donate one like this to my local thrift shops, they wouldn't even take it...

 

[cowboybob]

Google is your friend: all I did was enter "itt nokia 3722 os ideal color manual" in the search line and the #2 listing was this: https://elektrotanya.com/nokia_core_kit_mn_nr_chassis_3722_os_ideal_color_tv_sm.pdf/download.html. There were other options as well.

Now, I should say that I agree with Nigel and MikeMI, so proceed at your own risk.

 

[J_Nichols]

Google is your friend: all I did was enter "itt nokia 3722 os ideal color manual" in the search line and the #2 listing was this: https://elektrotanya.com/nokia_core_kit_mn_nr_chassis_3722_os_ideal_color_tv_sm.pdf/download.html. There were other options as well.

Now, I should say that I agree with Nigel and MikeMI, so proceed at your own risk.

Thank you very much for the paper.

Well, repairing it cost 20 bucks, and a new one (second hand is the same or even less price).

If it's too difficult for me I won't repair it. But if it's easy I will.

 

[MaxHeadRoom78]

I would eliminate the power supply first, it is usually on a board by itself, disconnect the outgoing DC supplies and see if the fuse stays intact, if it does it is further into the set.
If it does blow then you have a P.S. problem.
Max.

 

[alec_t]

If the power supply does start up, BEWARE. There are LETHAL voltages inside a working CRT TV.

 

[J_Nichols]

I would eliminate the power supply first, it is usually on a board by itself, disconnect the outgoing DC supplies and see if the fuse stays intact, if it does it is further into the set.
If it does blow then you have a P.S. problem.
Max.

Ok, I will try to extract the P.S. and ask here what to test.

 

[J_Nichols]

I would eliminate the power supply first, it is usually on a board by itself, disconnect the outgoing DC supplies and see if the fuse stays intact, if it does it is further into the set.
If it does blow then you have a P.S. problem.
Max.

I will try it.
I have seen in youtube a man that says that usually that problem is on the PTC. He said that one of the first steps is to disconnect the wire from the PTC to the coil and turn on the TV. If the TV works, it's from the PTC.
But I agree with you too. I have localized the P.S. and I will try also the advice you said to me.

 

[J_Nichols]

I have recorded a video to see better what I mean. Sorry for my english.
I have disconnected 4 cables
3 cables from a board (small board connected to the big board)
1 cable from a big board (not P.S)

About the fuse, I mean that the fuse has exploded when I replaced it with a new one.

 

[cowboybob]

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.

 

[JimB]

Where is TVTECH* when you need him?

* The South African "King of CRT TV repair".

JimB