Weird problem with Sony KV-20FV12

[old_coot88]

Originally Posted by zeno

Sony AKB circuits will mute the pix if a bad CRT but
I will assume yours is OK. Usually the pix blinks
when cold & does it less with warm up.
It is also sensitive to the G-2 setting so turn it up a tad
& see what happens. Basicly if any gun cant draw enuf
current the jungle IC shuts off all Y & C. During blanking
each gun is fired & current measured. You can usually see
three color lines at the top if you shrink the vert a little.

The CRT should have about 125V on the cathodes with
normal pix & 200V no pix ( zero beam ), G-2 abt 500V any pix.
Dont remember what the G-1 did in these.

73 Zeno

There's no change in pic size or geometry, or in chroma or video content. The CRT socket readings are-

Heater 5.2 VAC constant, and no change in the orange glow of the cathodes.
All G1s 51V constant.
Cathodes constant 150V with no pic, with pic they fluctuate 130V-170V with scene content.
G2 700V constant (G2 control painted solid, can't turn it).

Seems like totally normal readings. And they do not change during the half-minute "cycle" between a normal, bright pic and the washed-out "extremely weak CRT" image.
There's no intermittency or abruptness, and no response to tapping the boards or CRT neck. Just the slow, gradual 'cycling' between the two states.

All I can figger it must somehow be the jug doing it. Prolly just junk the set.

[Findm-Keepm]

Solder connections okay?

Solder connections at the CRT socket were bad on my daily watcher 20" Sony. My daughter thought I was messing with the remote - to prove her wrong, she did the soldering....

The solder connections on the CRT board were quite solder starved.

[jr_tech]

Something has got to be changing... corroded CRT pins, perhaps ???

jr