Greenish Sony CRT TV

[Mr RB]

General one-colour fault finding;
1. swap red and green wires going from motherboard to CRT neckboard
(if fault colour changes the problem is on motherboard, if still green fault the problem is on the neckboard or CRT).
2. swap the red and green driver transistors on the neckboard, see if fault swaps
(if fault is still green it's probably a cathode short in the tube, or maybe bad socket/dry joint)
3. if tube fault try tapping tube neck to see if it comes and goes, sometimes it can be fixed by tapping, with the tube upside down or on its face. I think it dislodges tiny metal corrosion whiskers etc.

I heard about one TV tech that used to put tubes with shorted cathodes out in the sun for a few weeks, sitting on the tube face (neck pointing up). I think the theory was that the hot sun causing expension contraction etc could fix some cathod shorts. Could also be a myth, I can't remember who told me but it was someone in the TV tech industry.

I have actually fixed some tubes by the tapping method, more than half were permentently fixed. One I had as a shop tv and it used to relapse and needed tapping again every couple of months.

 

[dark666]

Hi all.

Thanks for all your replays.
Once i have the time, i'm gonna try your ideas and hints for repairing the TV.

 

[ghostman11]

what size hamer do you use to tap the neck?

 

[Mr RB]

Just using the plastic handle of a typical screwdriver, tapped lightly.

Although the neck is the "delicate" part of a tube they won't break from some light tapping.