Worn CRT or other issue? (Sony)

[zeno]

1) on the CRT board there are 3 identical 2W resistors. They feed the
R,G & B outputs. Where they join is apx 200VDC. Follow that line & you
will come to a cap typ 4.7 mfd 350 volts. change it.
2) check resistors off the G-2 control. High ohm values & they like to
open.
3) blue line at top is probably the AKB ( automatic kine bias) firing.
With AKB each gun is fired & measured during retrace & automaticly
adjusts the grey scale. Normaly on a Sony with AKB & a weak CRT
the video will blink on & off but less as the set warms.
4) keep in mind the cathode voltages will all be a little different.
The lower the voltage the higher the brightness of that color.

73 Zeno
LFOD !

[grossbard]

Originally Posted by old_coot88

I had a similar tracking issue in a KV-20FV12, caused by a soft CRT. The cure would be to raise the CRT heater voltage a bit. Not being a Sony specialist, I didn't know if there's a resistor in series with the CRT heaters (as there is in many brands). It would be a small value, like 2 - 3 ohms, and would be on the neck board. So I asked the Sony gurus on here, and sure enough there is. So I jumpered that resistor an lo, the Jug came right up and looks great to this day. If yours has that resistor, try jumping it temporarily and see if the tracking improves.

I assume it's R704 in this picture? You mean you removed the resistor and jumped the two points with a wire? I might try that.

Originally Posted by zeno

1) on the CRT board there are 3 identical 2W resistors. They feed the
R,G & B outputs. Where they join is apx 200VDC. Follow that line & you
will come to a cap typ 4.7 mfd 350 volts. change it.
2) check resistors off the G-2 control. High ohm values & they like to
open.
3) blue line at top is probably the AKB ( automatic kine bias) firing.
With AKB each gun is fired & measured during retrace & automaticly
adjusts the grey scale. Normaly on a Sony with AKB & a weak CRT
the video will blink on & off but less as the set warms.
4) keep in mind the cathode voltages will all be a little different.
The lower the voltage the higher the brightness of that color.

73 Zeno
LFOD !

Thanks for the info as always! I forgot to mention that I replaced all of the resistors around the G2, as I had read somewhere else that those can go bad. I didn't find any caps with the value of 4.7uf 350v. According to the service manual, the highest value cap with 4.7uf is c523 4.7uf 160v. I think I changed that one already but I'd have to go back and look.

Here's the service manual if anyone is interested.

https://drive.google.com/file/d/19P2...ew?usp=sharing

[old_coot88]

Originally Posted by grossbard

I assume it's R704 in this picture? You mean you removed the resistor and jumped the two points with a wire?

Yep, that's the one. I left the resistor in place and jumpered it with a wire.

[zeno]

follow the 200 v line down to the main PCB. It should be near
the FBT. Its a common problem on all brands.