1971 GE Portacolor H3 chassis color help

[wabr101]

TV has had some new caps and tubes. Gray scale is great. Color comes and goes. If I turn channel off and back on color usually returns-or if I fine tune to sound in picture-color returns. Voltages normal-if color goes, screen looks green unless color control is turned full counter clockwise? Tubes were subbed-no changed.
Seems like detuning or turning channel to 3 and back to 4 etc shocks color into working temporarily. Any ideas?

[zeno]

Try this it will eliminate the tuner.
Put signal on & tune the fine tune until the pix gets wormy.
You should still have color. Watch it over time for drift.
Almost sounds like you have 2 problems.
BTW these rear controls get tin wiskers. Shango did a Utube on it.

73 Zeno
LFOD !

[wabr101]

Color goes away until I tune it for wormy again.

[zeno]

OK you set it to wormy & watch it. the worms go away & you
have to fine tune to get them back. If thats the case you have
tuner drift so ignore the rest of the set for now.

You can
1) clean the tuner
2) clean the 2 tube sockets. Pull the tubes, spray sockets then put the
tubes in & out a few times.
3) Get a NOS mixer / osc tube, thats most likely. If the RF amp is cheap
change that too.

good luck
Zeno

[wabr101]

Not the tuner. The picture can stay wormy and color fades.
I have to make the picture wormy to get color BACK. Its like the color oscillator, a crystal needs an electronic punch to get color back. In short oscillator does not stay oscillating.

[Electronic M]

I think you two may be speaking different languages. Your interpreting wormy as Barber poling (chroma Osc out of sync), and I think Zeno means the monochrome portion of the picture is wormy and color doesn't Barber Pole.

It's not uncommon for a slightly misadjusted chroma Osc to loose sync when color signal isn't at it's peak on the fine tuning.... What I typically do when that happens is locate the chroma Osc slug on the schematic/in the set, get a full screen color bars test pattern on screen, turn color to max and detune the fine tuning till the barber poling is barely visible enough to make an adjustment then get it adjusted to sync like that.
EDIT: I just remembered this is a GE...They don't use a color osc and instead they amplify the burst and feed it into a coil that rings (resonates) at chroma osc frequency for longer than 1 horizontal line....Not sure how those get out of sync... Maybe the resonant coil is adjustable and needs tuning or the burst gate isn't working properly.

[old_coot88]

Originally Posted by Electronic M

.They don't use a color osc and instead they amplify the burst and feed it into a coil that rings (resonates) at chroma osc frequency for longer than 1 horizontal line.....

Doesn't the ringer circuit also incorporate a 3.58 crystal?

[wabr101]

There is no barber pole effect. Color comes on when I tune fine tune to sound in the video. I back off fine tune and get a good picture. Color goes out after a minute or so. Gray scale is fine. It seems as if the chroma is going off, and stays off until I detune the tuner and tune it back to a good picture. In other words, imagine losing color and then you change the channel and back again- it comes back for a minute. Oscillator for 3.58 doesn’t keep oscillating. How often do crystals go bad?

[old_coot88]

Sounds more like the chroma bandpass is being biased off. Does the set have a color killer adjustment? Hard to remember. Been a lotta years.

[wabr101]

No color killer in this set.