Westinghouse Color Oscillator Circuit

[Tom9589]

Why didn't other manufacturers use the color sync/oscillator circuit that Westinghouse used instead of the crystal oscillator circuit?

Long term stability? One fewer user controls? Patents?

[Yamamaya42]

Seems to me that the crystal osc, is the better way to do it.
The way Westinghouse did it seems more prone to drift.

[Electronic M]

If the Westinghouse required user to maintain color sync with a user control then it was a bad design(disclaimer I've never owned a Westinghouse TV and am not familiar with their circuits). Many users had confusion with even the simpler control schemes extra complexity is not a selling point.

I'm rather partial to the GE chroma ref circuit... just gate the color burst to a LC tank circuit that will once stimulated will ring on frequency and in phase for more than 1 horizontal line...it was cheaper and simpler than RCAs approach and just as stable and effective.

[zeno]

I dont remember that about them. Keep in mind W & GE both had the talent
& money to make the best TV's in the world. but they both decided to build
mostly junk. I could ask why on almost all GE sets the tint control worked
opposite of all other brands ! Its a mystery
Sorry if my opinions offend any fans of W & GE but I call them as I see them.
I also give credit where credit is due. Remember Armstrong climbing down the
LEM stairs ? That was a Westinghouse camera we watched it from.

73 Zeno
LFOD !

[Yamamaya42]

The only ref one can find is this, http://www.earlytelevision.org/pdf/w...ms_0259-15.pdf
and from what I see, it just seems like an odd way to do it.

[old_tv_nut]

Two capacitors in parallel are used to tune the oscillator coil, a 150pf and a 33pf.
My guess from the Aerovox part numbers is that the 150pf is NPO, and the 33pf is N750 (negative temperature coefficient, minus 750 ppm/deg C, +/- 120 ppm/deg C).

This was obviously needed to counter the temperature coefficient of the coil, and still would not guarantee stable enough operation to do away with the color sync control. I still can't help thinking this was a stupid design when crystals were readily available, even if it did avoid some patent or other (which I don't know it did).

However, when I say crystals were "readily available" I suspect that at the time they were only being made from natural quartz and were still much more expensive than a few years later when synthetic quartz was in use, so maybe a few 1950 dollars instead of under 50 cents.

[Tom9589]

Both the Westy and the early GE did not have easy user access to the tint control. They were located on the rear of those TVs. So the Westy had only two front access color controls: "Color and Color Hold" while the GE only had one: "Color."

[Electronic M]

It is possible the hold control could have had some tint functionality near the edges of it's locking range.

[old_tv_nut]

Originally Posted by Electronic M

It is possible the hold control could have had some tint functionality near the edges of it's locking range.

I think you mean dysfunctionality, like using horizontal hold to do picture centering.

[old_coot88]

Originally Posted by old_tv_nut

I think you mean dysfunctionality, like using horizontal hold to do picture centering.

...Sorta like keeping Nipkow disk motors in sync.

[Electronic M]

Originally Posted by old_tv_nut

I think you mean dysfunctionality, like using horizontal hold to do picture centering.

Yup! I didn't say it was good but it at least might have tried to make up for the rear tint control in its own haphazzard way.

[benman94]

Keep in mind that until color television matured in the 1960s, it wasn't exactly uncommon for a set with a PLL to loose color sync and start "barber polling" away, especially as the set aged. Period reviews of sets mention this from time to time. With this in mind I actually think the Westinghouse design is fairly elegant. Simply turn the color hold control until the color locks again.

And unlike hue and saturation controls, the Westy color sync control is trivial to adjust. There's only a single correct setting and lots of "wrong" settings. With hue and saturation, it isn't so cut and dry. The color acuity of the viewer has to be taken into account. I might set my sets up differently than someone with red-green colorblindness, or someone with better color acuity, say someone with light blue eyes.

[Tom9589]

I have owned a GE color TV and don't remember having to adjust the Tint control much. Maybe there is something to their 3.58 MHz ringing oscillator circuit.

Did any other manufacturer use this ringing circuit?

[old_tv_nut]

Really, phase locked loops (phase detector/oscillator) and ringing circuits can both be analyzed to determine the important operating characteristics of noise bandwidth, and phase shift vs. frequency offset. The only major difference is that the ringing circuit has no positive feedback to sustain output indefinitely in the absence of input. It is also possible to use an oscillator without a phase detector and lock the oscillator by injecting the burst (which some Motorola chassis did). Such injection-locked oscillators can also be analyzed to determine the same performance characteristics.

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