CRT TV - Blue spark inside glass neck related to focus

[Flybacks]

Hello, when I power on the TV there is a blue little spark inside the crt glass neck that increases and decreases in intensity with the focus, when focus pot is at minimum it is invisible when it is at max it is brighter and makes some dots on the screen appearing and disappearing randomly.
The picture is fine and the TV has no problems.

I've cleaned the crt plastic socket, pins and the spark gap contacts so I don't understand what could cause it

Could some more experienced member help me to troubleshoot it ?

Some picture attached for better understanding.

Many thanks

[angelos]

Re: CRT TV - Blue spark inside glass neck related to focus

I am not sure if i will hit the nail on the head but two things come to mind.
1. Your EHT is too high. I think it must be around 20KV but you would need some kind of probe to test that. If its the focus that's too high then it should be around 8 - 10 KV.
It could be a faulty LOPT.
2. There is carbon build up in the tube due to age. This you cannot fix but a tube rejuvenator might clear it up temporarily.

[Flybacks]

Re: CRT TV - Blue spark inside glass neck related to focus

I am not sure if i will hit the nail on the head but two things come to mind.
1. Your EHT is too high. I think it must be around 20KV but you would need some kind of probe to test that. If its the focus that's too high then it should be around 8 - 10 KV.
It could be a faulty LOPT.
2. There is carbon build up in the tube due to age. This you cannot fix but a tube rejuvenator might clear it up temporarily.

Hello, thanks for the reply.
I haven't an high voltage meter, but is it possible that the LOPT is faulty and the picture is fine except these little random dots with focus pot at max ?

[angelos]

Re: CRT TV - Blue spark inside glass neck related to focus

Can you take a picture of the image with the sparkles? Yes, LOPT can be bad but also tube.

[ivtec]

Re: CRT TV - Blue spark inside glass neck related to focus

Hello, thanks for the reply.
I haven't an high voltage meter, but is it possible that the LOPT is faulty and the picture is fine except these little random dots with focus pot at max ?

You must like old tubes tv very much,i did too but it's time to move on to some other new stuff, i had a 36 Sony hd tv and i liked it much but i had a few other lcd tvs so i decided to dich it when i had enough people to move it out of the 2d floor, because getting old, although it was working perfectly.

[Flybacks]

Re: CRT TV - Blue spark inside glass neck related to focus

Can you take a picture of the image with the sparkles? Yes, LOPT can be bad but also tube.

Hello, it isn't easy to take a picture because they are fast.
They are like little flashes of light appearing and disappearing when focus pot is at max and the blue spark inside the crt glass is brighter.
Is there a way to check if the tube is ok ?

[alfatv]

Re: CRT TV - Blue spark inside glass neck related to focus

The tube can't be good if you see spark inside it. Especially if picture is focused, but spark is still there.