CRT TV has brightness problem, need help to identify what is causing it

[nahuel0909]

Hi!
I have a Philco PM2014 (I attached the manual of the PM2024 model, which is the closes thing to my model I could find and they seem to be pretty similar).

The issue happens when I'm using the TV on AV mode, it does not seem to happen on cable mode.
Basically the screen goes brighter and dimmer randomly, usually after a few moments of usage the screen might go noticeably brighter and it will stay that way for some time. Then the brightness might go down again and stay that way for a few moments, then it might go dimmer than normal, so on and so on. It's very noticeable and annoying.

I already took it to someone who repairs a lot of these old TVs and he didn't find anything wrong and I belive this is because he tested the TV on cable mode, so my conclusion is that this only happens on AV mode. I don't know how weird this is but it might help identify the issue?

The things I did is cleaning the TV inside and messing around with the flyback transformer but nothing changed.
Also I'm pretty sure it's the TV and not my AV devices because it happens both with my PC that I connect using an HDMI to RCA adapter and with my PS2 as well.

If you need any information or pictures I can provide to help identify the issue let me know.

Thanks!

[james_s]

It sounds a lot like the effects of Macrovision analog copy protection, is the source material copy protected movies? Do you have any other displays that accept analog composite video to check with?

[nahuel0909]

I'm pretty sure its not any copy protection involved here

[james_s]

I just can't see how the fault would happen only using the baseband video input and not going through the tuner, the tuner will output a baseband video signal. I would look at anything in the input chain from the A/V jacks to whatever switching selects which input is used.