An old "Sony" Trinitron with a brownish image
 

Found for sale in another city (not close to Bucharest, unfourtenley) an '80's "Sony" Trinitron that haves a brownish image: https://www.youtube.com/watch?v=XPS9...ature=youtu.be
Is it because of some electronicall problem or the tube is worned out?

Interesting question! I had a "that vintage" Sony with a very warmish color
temperature, probably 5500-6000 K when most sets were perhaps 10,000K.
When I replaced my old Zenith I selected it out of dozens at the store
because of that fact. It looked different, and "right". I never ever
knew if it was intentional or some sort of mistake. It remained that way
until it died of a heater-cathode short. There was no problem with its
gray scale, it was that temperature at all brightnesses.

Poor blue gun performance?

It's hard to tell from the video. It could be the camera making the set look bad. I didn't see as many bad CRTs in the 14in sets - more common in the larger sets. When the CRTs did go bad all you were left with usually was a dim purple or green raster - I'm not seeing that in the video.

I still have one on a test bench that's been there for 10+ years now. When I found it way back when it did have a bad CRT (purple), but replacement CRT I pulled from a older model is still going strong.

If only the low-lights are brownish, it's a tracking problem. Adjusting G2 controls might fix it. But it could be that the tube is gone to the point where the controls cannot balance it.

Unless the seller already said that the TV's picture is brown-tinted, I think the most likely problem is just that the recorder (a cell phone, or a camcorder) made the video look bad. The details on the screen look sharp and clear, so the CRT is probably not weak overall. And, if the blue CRT gun is weak, usually a Sony set will try to compensate by boosting the blue signal. That boosting would make the black area on the screen have a dark gray or blue appearance, but this one still looks black. So, I think the CRT is probably good. But, you should go and see it if you can, before buying it.

Unfourtenley the set is not in Bucharest or a in a city near by and I don't know anyone in Arad. The train trip up and back to/from Arad would cost me unleas twice the price of the set.