Motorola roundie

[dtvmcdonald]

Originally Posted by old_tv_nut

I'm surprised that only one adjustment was needed.

With the fixed matrix resistors, you can adjust I/Q relative phase and the COLOR control to compensate for errors in one color matrix, say red. Then you still need I and Q gain adjustments in both green and blue to get them perfect, so that's four additional adjustments total.
If you insist on the I and Q waveforms being exactly correct, then you need I/Q ratio adjustments for errors in all three matrices, plus luma vs chroma gain adjustment in two of them, so that's five additional adjustments.
As you say, these adjustments can be avoided by the use of precision resistors in the matrices.

I'm not thinking as hard as I did when I actually did it.

I though about getting the signals right at the CRT.

First consider B&W, color turned off. Brightness sets black level for one color. the CRT brightness controls the other two black levels. Contrast and the blue and green video gains controls the peak brightness of the three CRT guns.

Thus the three B&W matrix resistors are arbitrary but now considered fixed.

There are six color matrix resistors. There are these color adjust controls:
Color saturation, user hue, I-Q phase difference, and I gain.

Hmmm ... unless I screwed up today, it looks like I needed two more adjustments rather than just one. But in any case, adjusting just one
of the matrix riesistors got it essentially correct.

In another view there really need to be two or three more adjustments, but there's no easy way to do these . Those are adjustments for the three gammas of the three CRT channels. Of course the relative settings of the three screens and the two video gains can do a bit of this, as could adjusting the fraction of DC restoration (R249/R273/R274 values, etc.) in each of the three channels (its intentionally not 100%).

Edit: There is one "gamma" tuning that RCA made, and that is the 2.7K resistor in the red CRT cathode. This may also be there
to save it from overdrive in grid conduction ... which is awfully easy to do!

On my set I have added little red and blue masking tape arrows to the brightness, contrast, hue, and color level controls.
The blue ones are my chosen "correct" settings, while the contrast, color level, and brightness have red ones that are placed
so that if I don't exceed them (with the others set at blue) there is never current through that 2.7 K resistor. If there IS current
through it, the CRT red cathode and red DC restorer clip both positive and negative red levels. These red arrows are placed
by using my scope in subtract mode with the DC level and gain of the inverted scope channel so there is zero deflection
with the two probes on the same side of the resistor.

[old_tv_nut]

By the way, back when I did an analog IC chroma demod/matrix design at Zenith (to provide RGB outputs for the unitized-gun CRTs), I had to use some (lousy) on-chip vertical PNP transistors in the color difference paths, and it was necessary to do a statistical analysis of the component matching of those as well as the matrix resistors to show that the 95% ellipsoids of color variation were not significant.

[timmy]

This Motorola I have has a faint white line 12 to 6 straight up and down position any thoughts how to fix this or troubleshoot.

[Yamamaya42]

Weakness or imbalance in the horizontal output tubes may do it, this moto is an odd set with the pair of 6JM6s.

[timmy]

Originally Posted by Yamamaya42

Weakness or imbalance in the horizontal output tubes may do it, this moto is an odd set with the pair of 6JM6s.

Well the tubes are new and I had the same line on the cbs Columbia and a slight adjustment of the horizontal frequency pot the line disappeared

[Yamamaya42]

Originally Posted by timmy

Well the tubes are new and I had the same line on the cbs Columbia and a slight adjustment of the horizontal frequency pot the line disappeared

My Stromberg Carlson X22 had the same sort of thing happen, faint white line when started, that would slowly fade after 20-30 min, caused by a weak/tired 6CU6 (11w max)
This went away after it was replaced with a slightly stronger 6GW6 (17.5W max)

Not sure if this is the same as your problem, but it may be similar symptom.

[timmy]

Is there a specific type of antenna for this Motorola color to get a clear picture because rabbit ears don’t seem to work well being it’s color maybe there should be an antenna specific to color

[old_tv_nut]

Originally Posted by timmy

Is there a specific type of antenna for this Motorola color to get a clear picture because rabbit ears don’t seem to work well being it’s color maybe there should be an antenna specific to color

What channel are you using?

There really is no specific "color" antenna, just as there's no such thing as a "digital" antenna. Generally an antenna is good or bad depending on the specific channel for both black and white and color.

[timmy]

Originally Posted by old_tv_nut

What channel are you using?

There really is no specific "color" antenna, just as there's no such thing as a "digital" antenna. Generally an antenna is good or bad depending on the specific channel for both black and white and color.

Using channel 3 putting cable signal in an antenna amplifier and output has an antenna and all my sets work and the color but it not clear

[old_tv_nut]

Low VHF is not the best for indoor antenna rabbit ears, as they are generally too short for the wavelength. If you can use high VHF or UHF you may get better results.

[timmy]

I have an antenna 15 feet any from the set so what do you mean by a high vhf antenna or channel

[kvflyer]

Originally Posted by timmy

I have an antenna 15 feet any from the set so what do you mean by a high vhf antenna or channel

Does this answer the question?

"The VHF band is further divided into two frequency ranges: VHF low band (Band I) between 54 and 88 MHz, containing channels 2 through 6, and VHF high band (Band III) between 174 and 216 MHz, containing channels 7 through 13"

[Yamamaya42]

Originally Posted by kvflyer

Does this answer the question?

"The VHF band is further divided into two frequency ranges: VHF low band (Band I) between 54 and 88 MHz, containing channels 2 through 6, and VHF high band (Band III) between 174 and 216 MHz, containing channels 7 through 13"

and they crammed the USA FM radio band right in between them!

[Yamamaya42]

Channels 3-4 are best avoided if used over air, as RFI plays havoc with that range, direct RF coax should be OK for 3-4, but over air will always be a pain, I have a BT modulator that outputs on channel 7, which is a lot clearer, but 11-12-13 would be even better.

[timmy]

Originally Posted by Yamamaya42

Channels 3-4 are best avoided if used over air, as RFI plays havoc with that range, direct RF coax should be OK for 3-4, but over air will always be a pain, I have a BT modulator that outputs on channel 7, which is a lot clearer, but 11-12-13 would be even better.

BT modulator ?