Need help with an old CRT TV

[Ivan Ujkić]

Yesterday I pulled out my old colour CRT TV from my grandmas basement - well, from next to the basement - it was sitting in the rain for a day or two with some blanket over it. When I took the back cover off it it was absolutely filled with dust. Dust that I couldn't even blow off with a compressor, I had to scrub it off. I turned it on and plugged in an antenna about a year ago before that (when there was still analog TV service) and the picture was totally fine - but no sound. So yesterday I took it apart and looked for a cable break or anything burnt, but all I found was dust, nothing interesting. Put it back together, plugged it in an outlet, pushed the button and it started right up no problem. Only then did I realise that I was looking in the wrong place for the sound problem - it was just a crappy BNC connector. About 24h later (today) I plugged it in again and started it up. I only saw a few fuzzy lines at the bottom of the screen, the CRT started glowing like a vacuum tube (not sure if it's supposed to do that, but I didn't notice it before), and then the screen just shut itself off like it would if I turned it off, but I didn't. The little indicator light was still on so I just turned it off on the button. While the TV was sitting in the garage for 24 hours it shouldn't have collected much dust and definitley no water got in it. I highly doubt anybody touched it in that time either. I was stupid enough not to take a picture of the model number of the CRT or the TV. Ill post them tomorrow ASAP. Have a bunch of pictures of the TV too.

 

[73's de Edd]

Sir Ivan Ujkić . . . . . . .

WOW . . . . how does anyone in those dusty environs, and their lungs taking that in . . .not be having some serious long time respiratory problems.
There are some circuitry points that you DO NOT want that residue being across connections.

Your second photo down shows the kine driver board . . . .the white socket to the kine wants to be clean along with the heavy red andwhite wires on it.
Also you see some critical areas that they have machine routed slots into the circuit board . . . to isolate a possibility of any arc over there.

Your 14th photo down shows your fly back transformer, over to the left, with its heavy RED high voltage wire coming out from its top.
All of that unit and its nearby area, needs to be clean of any conductive contaminants.

I was looking for a set of right and left wires from your units speakers to come in and plug in nearby to your audio output circuitry, but that was not being positively identifiable

Pity that the units picture display went out, as the sound area would be the MUCH easier of the two areas to fix.



73's de Edd

 

[Ivan Ujkić]

Finally got the TV model number! (I was really busy last week). the model number is AV-28WFT1EKS Also I forgot to mention - when I turn the TV on now, I don't hear that high pitch whine that (I'm pretty sure) comes from the big capacitor connected to the CRT with a big red wire.

 

[davenn]

I don't hear that high pitch whine that (I'm pretty sure) comes from the big capacitor connected to the CRT with a big red wire.

No, that's the line output transformer and that red cable carries around 25,000 volts to the picture tube



gosh, there's so many different things that could kill the pic side of things
As Edd say, much easier to fix a sound fault


things it could be....
the pic tube
the line output transformer
the chopper transistor for that transformer or both
a main power supply fault

and a number of other things

Unless you have significant electronics experience, particularly in CRT TV's and test equip. I would advise you that it isn't likely worth continuing

Even before starting fault finding, ALL boards should be removed and washed down and then left to thoroughly dry out
All that muck has to go. If it hasn't already, it is likely to cause faults


Dave