The picture tube is very likely getting bad. You need a Tech to look at
it.
You have two choices....the Tech does I mean. Read my post from a
while ago. Dani.

I would like to share this great tip with all you great helpfull Tech's

out there! This is only for Technicians who really know there way
around the inside of a T.V.! Please don't just anyone try this!! If you

don't have a proper CRT rejuvinating set, this will be a great fix, for

an otherwise lost cause.

Sony 1 K problems, that is T.V.'s with the red, or green, or blue
having too low, or high of an emission to get a raster due to the
"blanking circuit", can be solved with an odd, & somewhat dangerous
technique! With the set off, unsolder each cathode on the CRT board,
then momentarily bridge the gap of each gun, one at a time, to see how
much emission there is. You will have to raise the G 2 pot to get a bit

of raster in a darkened room! Next solder the two good cathodes
(usually only one is out of gain specs), back, leaving the bad one. Now

this is where it gets dangerous!!! While the set is off remove the
focus line from the CRT socket ( 5000 volts), & while the set is
running, momentarily make contact with the unsoldered leg of the bad
gun. Do this with caution, & at least five times. It will try to arc,
but just keep a steady hand, & keep the wire with a good insulated tool

at the unsoldered leg only. Now, while the set is off, unhook the G 2
wire, & set it to about 200 volts DC unloaded, & charge a 100 uf
capacitor @ 250 volts. Do this two, or three times, then discharge it
to the unsoldered gun, while the set is runing. Do this charging, &
discharging to the gun at least five times! At this point, you should
see the bad gun get brighter, & brighter. I have done quite a lot of
experimenting, & this will save a lot of those Sony CRT's, that would
otherwise be toast. Grey scale comes back to within a close enough
spec, to make the customer happy. Just don't give a long warranty. Hope

this helps you all out. Take care, Dani.