I have replaced the out of spec capacitors but get the same response. Something interesting; the directions state to set the color level to the mid-point, I found turning the color level to approx 1/4 I could get a much better response curve.

I pulled the lead on the color level pot and did some measuring, the spec is 25k, mine measures 1.78 ohms to 29.624k. The taper appears to be a steep logarithmic curve, my mid-point measures 1.375k, and the 1/4 setting is approx 700 ohms. Someone with math skills could probably calculate what the midpoint value should be for a 25k pot. Directionally I know my midpoint is shifted up since my pot measures high.

https://i.imgur.com/djfD8I2.png

SAMS shows the color level replacement as Mallory part number PP253R which uses their #2 right hand logarithmic taper. The chart shows at 50% it should be at 90% resistance (2.5K where mine measures 1.375K). Now it's possible that Zenith used a special logarithmic taper and the Mallory part is all that was available for the aftermarket.

It's odd that my pot being 20% high measures lower than what the Mallory chart says it should be but also odd I need way less resistance to get a good curve (300 to 700 ohms is the range that appears to be a happy medium when adjusting L17 and L19 yield a proper response curve).

Should I move on or does having to set the color level way high (1/4 turn from max) suggest there are other problems?

*Edit* The other factor is the signal level from the B&K 415 going into C1, I have it maxed out but as I turn it up I am able to back off the color level just a small bit. I suspect the only issue is I don't have enough signal strength going in. :( In the subsequent Zenith Service Manual (CM-107) for the next roundie series chassis the directions include a note that the signal generator and scope may need to be set near the maximum, but don't overload.

https://i.imgur.com/2xQ6Z5V.png

Are there any instructions for tuning L18? The symbol indicates it is tunable. Since the odd response occurs when adjusting the color level control in parallel with it, L18 may be the problem.

I would not be concerned about the mismatch of the log curve as long as it is in the right direction.

I'm guessing now that L18 is supposed to be self-resonant at 3.58 MHz, and the purpose of setting L19 to minimum at 3.58 MHz is to flatten that peak. So, it looks to me like L18 is tuned to too high a frequency. When you turn the color level, the peak should go up and down at 3.58 MHz, not at the higher frequency shown.

Continuing along the next few steps went well.

Color Sync Alignment

• Color switch on, color level set to the halfway point
• Color Bar generator connected to antenna terminals set to Color Bar Pattern
• Connect a .01uf capacitor from test point L to ground
• Ground test point K
• Adjust L34 for zero beat on screen and minimum movement of color bars through picture (they were visible and a very slight adjustment removed these)
• Next set VTVM to +50v DC range
• Connect VTVM to test point V, adjust T20 top slug for maximum indication (very little adjustment was needed)
• Connect VTVM to test point V, adjust T20 bottom slug for minimum indication (very little adjustment was needed here too)
• Note T20 slugs should be on outside end of coil not towards the middle
• Remove ground from Test Point K and .01uf capacitor from test point L
• Color switch on, color level set to the halfway point
• Color Bar generator connected to antenna terminals set to Gated Rainbow
• Connect scope to test point R, adjust L29 Burst Amplifier Plate coil to match Figure 15A (a small amount of adjustment was needed)
• The second and forth bars should be equal in amplitude
• https://i.imgur.com/PtsJDdZ.jpg
• Connect scope to test point S
• If needed touch up T20 bottom slug quadrature coil to match 15B (a small amount of adjustment was needed)
• 5th and 7th bars equal in amplitude
• Note slug should require a very minimal amount of adjustment
• https://i.imgur.com/eqDMPAr.jpg

Color Level Adjustment

• Color Bar generator connected to antenna terminals set to Color Test Pattern
• Connect scope to test point R and set color level to minimum
• Adjust L18 for minimum color output at test point R (a very small amount of adjustment was needed)
• Essentially the picture should be black and white only

Range Check of Hue Control

• Color Bar generator connected to antenna terminals set to Gated Rainbow
• Connect scope to test point R and set hue control to maximum counter clockwise
• First and third color bars should be equal in amplitude (second color bar maximum)
• If not touch up L29 Burst Amplifier Plate coil for equal amplitude of first and third color bars (a very small amount of adjustment was needed)
• Connect scope to test point R and set hue control to maximum clockwise
• 4th and 5th color bars should be equal in amplitude (they were)
• Note if only the 3rd and 5th color bars can be made equal than this is acceptable
• Connect scope to test point R
• Set hue control for equal amplitude of 2nd and 4th (3rd color bar at maximum)
• Now connect scope to test point T
• Color pattern should appear as shown in figure 15C (No pic but it matched)
• https://i.imgur.com/GQNDsg4.jpg

Alignment Points
https://i.imgur.com/whehTAk.png

I just posted the next few alignment steps as I just moved along for now with the color amp alignment as-is. I will go back and see what interactions I can get with the color level, L18, and L19. Note L18 measures ok so I believe it to be good. Also note the voltage going in at C1 from the B&K 415 is 0.3207 volts.

After going through the other alignment steps here is what the Video Amp test point U with the color level set at the half-way point, it looks better than before.

https://i.imgur.com/ziRmbQX.jpg

Also here are some videos (note they should open in Imgur, let me know if they don't work)

• Adjusting the B&K 425 signal down to zero and then back to max, curious if more B&K 415 gain would prove a better response curve: https://imgur.com/jmoT9J0
• Color level starting at the minimum and then turning the potentiometer to the maximum: https://imgur.com/5RBpapN
• Adjusting L19 (2nd color amp) which should be adjusted for minimum 3.58mc response. I starting with the slug at the top and turned it down to the bottom: https://imgur.com/lVtZ9qK

First video: looks like maximum 415 drive is overloading the set and giving a false flattening of the curve by crushing the peak. Don't try for higher, in fact make sure it's not too much.

Second video: yikes what mess! Stick with the suggested half-way setting for now.

Third video: There is only one point that gives a symmetrical response about 3.58 MHz?

Seeing the correct two nulls for L19 may be confused because you aren't changing the damping resistor.

Again, this suggests to me to adjust L18 so the peak goes up and down at 3.58 with color level adjustment, and adjusting L19 in conjunction with L18 for most symmetrical response.

I tried adjusting L18 with the goal of having the 3.58mc peak go up and down with color level adjustment. I also kept the B&K 415 signal turned down a bit from max. I don't know that I got it much better, video: https://imgur.com/A9hrDx1

I have checked all of the parts in the color amp circuits and I believe they are good, I have tried alternate 1st & 2nd color amp tubes, and made coil adjustments but the 4.1mc marker always has a much stronger response and it takes the color level at about 70-75% before the curve looks correct. Note probably unrelated but the last step of the color alignment is the 3.58mc traps which I got confused on and did not adjust the traps yet.

I will reset, look everything over, try again, and report back. old_tv_nut, thank you.

OK, but after adjusting L18, did you try readjusting L19 to get things flatter?

A few more actions and notes:

• L18 (Color Level Coil) - tried to adjust it against different L19 and L17 coil settings. At the extreme it amplifies the 4.08mc marker which does not help, for now I settled on when the color level is set to the minimum then setting L18 to have what would be the 3.63mc marker at minimum which leaves the 4.08mc and 3.08mc markers at the same level, this is also about what is done in the Zenith color level directions, example below. Note this image is with with the B&K 415 signal turned up, at lower settings this is a flat response.
• https://i.imgur.com/jR82zGz.png
• L19 (2nd Color Amp Coil) - when adjusting the slug starting with it at the top (nearest to chassis) the 3.58mc marker has the largest response (like a bell curve) with the 3.08mc and 4.08mc markers both lower. As I turn the slug down the 3.58mc start to fall, previously I kept turning the slug until the 3.58mc marker was just to as low as it would go. In doing this the 4.08mc markers would gain strength and throw the curve off, extreme example below.
• https://i.imgur.com/NViTFYf.png
• Today for L19 I instead only turned the slug down until the 3.58mc marker just fell below the 4.08mc marker, note the 3.58mc marker can be further decreased but at the expense of the over all curve, maybe this is a 1st of the two dips that would be seen with the VTVM.
• L17 (1st Color Amp Coil) - As I adjust this coil there appears to be a center area on the slug which brings the 3.58mc marker to it lowest and then starts to provides some over all curve gain, eventually the 3.08mc marker starts to drop off, I stopped right before this point. Further adjustment will cause the 4.08mc and 3.58mc markers to increase but then the 3.08mc marker will start to decrease.
• Note no combination of adjusting coils would yield individually strengthening the 3.08mc marker response.
• The strength level of the B&K 415 does affect the curve, would it be fair to assume that I should keep the level turned down so that at max color level there is no clipping?
• Several videos below, note I feel like the color amps are turned way down, i.e. the previous setting provided lots (maybe 2x) gain, maybe that is ok...
• Here is a video starting with the color level at minimum and going to maximum, note I have the B&K 415 signal strength set so that a maximum color level there is no apparent clipping (curve flattening): https://imgur.com/YFLdxcx
• Here is a similar video starting with the color level at minimum and going to maximum, but have the B&K 415 signal strength set to maximum: https://imgur.com/l563K5B
• Finally here is where I have landed for now: the response curve with color level set to the midpoint and the B&K 415 signal strength set to avoid clipping.
  https://i.imgur.com/2gv49wR.jpg

One option would be to pull the 8.2k resistor, add the 100k resistor and via a VTVM adjust the 2nd color amp coil to the 1st dip (nearest the chassis). I am confused by the directions, it notes to disable the sweep but to pass in the 3.63mc marker, the B&K 415 combines these functions so not sure how I would do this. What is the VTVM measuring, I assume overall voltage. Does a single marker act like a signal generator?
https://i.imgur.com/hplROKV.jpg

Would there be an affect on the color amp response from the other color circuits such as the oscillator or demodulator? To get the TV up and running I avoided replacing most all ceramic capacitors. Below are the ones that measured way off.

• C92 & C93 - all 4 .001uf measured 18-21% low
• C103 - .001uf measured 19% low, is this just for bypass? or would this affect the 3.58 oscillator
• C104 - 100pf measured 17% high but this was measuring in circuit, I suspect this will measure right on if I pull a lead
• C67 - 100pf measured 28% high but this was measuring in circuit, same thing I suspect this will measure right on if I pull a lead
• C69 - .001uf measured 18% low
• Note capacitors under 100pf may have measured high or low but without pulling them complete out they are hard to measure and I am assuming they are ok.

https://i.imgur.com/ovZnhb2.png

https://imgur.com/YFLdxcx -- increase is linear, shape doesn't change - very good measurement conditions.

https://imgur.com/l563K5B -- obviously overdriving and distorting at higher levels

"Would there be an affect on the color amp response from the other color circuits such as the oscillator or demodulator?" - No.

"where I have landed for now" - I'd say leave it this way for now and see how the picture looks, but it still is strange that you cannot get the response higher at 3.08 MHz.

Could you remind me where on the schematic is the sweep signal injected?

Sweep injection for the color amp alignment is at C1 which is just after the IF picture detector diode. This bypasses all of the IF alignment circuitry accept the 4.5mc filter (which I fiddled with just to see if it had an affect, nope it just shifts response curve left or right of the 4.5mc marker)

I agree it is strange I can not get the response higher at 3.08mc. I would like to think it is not something dumb with my testing setup or tools. Thinking though could an out of spec coupling capacitor pass but attenuate part of the frequency response? Otherwise I am looking at LC circuits which all have been gone through.

Could I create a test point after the first color amp circuit, or at other points to see where I lose the response? Thoughts on where in the circuit?

For Reference here is the full Zenith CM-106 Service Manual Schematic: https://i.imgur.com/i1nBrxi.jpg

Here is what I get off of the cathode of the 2nd color amp tube and a 150 ohm resistor (measured here as this resistor is soldered into a pin that is assessable from the top. Color level set to mid-point, I will assume the peak is at 3.63mc, here too the 3.08mc has a reduced response. As expected at max color level there is no signal as the pot goes to zero. Adjusting L17 only increases or decreases the overall response curve while holding the 3.63mc marker at the peak. I also tried to measure at Pin 7 of the first color amp but the signal was too low to really measure.

With the directions for L19 to minimize the 3.58mc marker I assume that leaves the earlier circuitry to provide an overall response curve wide enough to cover 3.08mc through 4.08mc. Here with the 1st color amp the center point seems like it should be shifted in frequency a bit lower.

https://i.imgur.com/pVjCH4J.png

https://i.imgur.com/pahZLPM.png

Reading the Color TV Training Manual 3rd Edition. Below is the overview for the chroma bandpass amplifier. Conveniently they picked a Zenith circuit as an example, they note is that the 7pf capacitor blocks the luminance signal, if this capacitor was off spec a bit could it attenuate towards the 3.08mc signal?

https://i.imgur.com/CswcpyD.jpg

One more post from reading Basic Televisions Principles and Servicing Forth Edition. Here their section on the chroma bandpass explains that the chroma amplifier circuit should peak a little above 4.1mc so when fed from the IF circuit you get the typical textbook response. This would still suggest the response I get out of the 1st chroma amp is not peaked correctly, so who know what the issue is with my chassis.

https://i.imgur.com/q6zAbLJ.jpg

https://i.imgur.com/3VVROr0.jpg

The reponse at the "new test point" (top of color level control) confuses me. If it is supposed to control color level, its peak effect (due to L18 resonance) should be at 3.58, in my opinion. I can't understand why they would want the symmetry of the response to change with color level setting.

Try this: change your test point to the cathode of the second amp (pin 6 above the 150 ohm) and turn the color level to max to take L18 out of action. See what the response is and what effect tuning L17 has. Then maybe we can go from there.

"the chroma amplifier circuit should peak a little above 4.1mc"
True, and I would expect to see that if you look at the 2nd amp cathode with the color level set to max. However, I would then still expect to see L18 tuned to 3,58 MHz so that the whole sloped response goes up and down with the color level control.

Note that this means that you would still expect to see a sloped response at the final test point (cathode of the R-Y Demod) because the injected 3.58 sweep has not been RF modulated and passed through the IF. So this makes the illustrations of final flat response suspect.

Note the text "If you were to align only the chroma bandpass amplifier...this method is rarely used however." So they are recommending injecting an IF sweep instead of the 3.58 MHz sweep. AND the symmetrical sketches shown with the 3.58 sweep injection are bogus.

So two important comments were made tonight, the extra studying was good too:

These made me go back and think about the signal going in. So the B&K 415 output has several setting, I assumed since I am feeding in signal post video detector I should use the video function. I just changed the output function to IF. Am I on the right track here? Note now I need to have the B&K 415 gain set to max. See below for the same setup just switching the output function setting and signal attenuation.

https://i.imgur.com/nEXvkwB.png

https://i.imgur.com/BHZhvQO.png

The B&K 415 manual does outline using the video function for the chroma circuit alignment, so I'm not sure what to think, it is also possible there is an issue with my B&K 415 :(. Maybe others with a B&K 415 can chime in. Note section 8.5.3 goes on to say its easiest to just continue on from IF alignment to chroma alignment by keeping the signal probe connected to the tuner (I assume here is when you would keep the function set to IF), then simply switch to the demod probe and continue on.

https://i.imgur.com/1thSozc.jpg

Ok, when you switch the B&K to IF but inject at C1, you apparently get some video detection action, I guess. But there's no telling if it is loading any traps correctly.

The next thing I would try is leaving the B&K output set for IF but moving the injection point to the IF input/mixer test point. With all the IF and trap stages in operation, it may make the curve even closer to ideal.

Question: when you changed output to IF, did you need to adjust sweep width/centering to get the chroma bandpass curve centered on the scope?

I would agree and will do this next. Thank you.

Stay tuned for a troubleshooting interruption. While still connected at C1 I was double checking the response curve and the waveform started to get erratic and now only has a minimal response curve. I pulled the test equipment and I have a very blue screen and basically no color, something failed.

Not sure what the root issue(s) were with the problems I had. As noted above first there was an issue with the color amp signal which occurred as I adjusted the Heathkit IG-5240 pocket signal generator, I fiddled with the controls which maybe was my problems.

From there after pulling and putting the chassis back in the issues changed to diagonal lines of signal against a white screen and then later a bright but faint image. The IF and color amp signals now looked correct so I poked around in the AGC and video circuit, all parts in these circuits measured ok. The Zenith Color TV Service Manual by R.L. Goodman has a section on actual issues and resolutions. One issue noted: Washed-out picture, no sync. AGC, sync trouble. Set may have to warm up before picture fades out. The cause was a leaky or shorted .01uf capacitor at grid, pin 5 of the sync - AGC tube. The capacitor tested ok but regardless I replaced it, was this the issue, I don't know but the set is back working.

https://i.imgur.com/91ELGGf.png

Back to the alignment:
I did not need to change the sweep width/centering. The only change needed is with the signal output and scope vertical settings to get the response curve to show well on the scope screen. The Zenith Service manual does not show what the curve response should look like when feeding the sweep generator through the tuner and IF sections but I assume it looks good. I still get a lower response for the 3.08mc marker when connecting at C1, maybe this is an artifact of the test equipment? Note when connected at the tuner adjusting L17 does a nice job of balancing the 3.08mc and 4.08mc markers, I assume they should have an even response.

https://i.imgur.com/jky4Opv.png

Question: Which input should I trust for the color amp alignment in regards to feeding the B&K 415 signal into the tuner vs test point C1 (post video detector)?

Connecting the B&K 415 to the tuner with the output set to IF I can adjust L19 to where I see the 3.58mc marker decrease and then have a defined low spot, also L17 allows me to create a flat-ish response with the 3.08mc and 4.08mc markers even.

Below is the optimized response curve with the B&K 415 signal input at the tuner, the 3.58mc marker is at its lowest response, and then the 3.08mc and 4.08mc markers are even. The 2nd pic is then the resultant response curve when moving the input to C1 and setting the output to video, note leaving it on IF works but barely yields a response curve. I am inclined to think I have it set correct this way and the "odd" response curve at C1 is due to the B&K 415 vs a mis-alignment.

https://i.imgur.com/wYuARxf.png

Your final result with the B&K 415 input to the tuner is obviously correct.

It's the overall result of signal going through the whole chain from tuner to picture that needs to be correct. The odd result when going in at C1 may be the result of the video detector circuit being loaded by the signal cable, plus, it is possible that both the SAMS and the Zenith documents are screwed up in not recognizing that the chroma bandpass by itself should have a tilt that compensates for the IF response.

Declare victory and move on!

I went back through the subsequent color alignment steps to double check everything. I posted directions back a few pages. The only notable item was for the color sync alignment you adjust L34 for zero beat on screen and minimum movement of color bars through picture. This was very dependent on fine tuning and my rf converter and signal bar generator both require a bit of different fine tuning. Adjusting to the signal bar generator probably means the rf converter could be off, maybe there is plenty of "wiggle" room with this adjustment.

The last color alignment step is to adjust the 3.58mc traps. The directions are to connect a color bar generator to the antenna, connect the scope to test points RR, SS, & TT and adjust each trap for minimum for minimum 3.58mc response. My question, what am I looking at on the scope and what component is the 3.58mc response?

https://i.imgur.com/WjX0PVz.png

https://i.imgur.com/ESb7bky.png

1) It seems odd that the color oscillator beat frequency should be affected by fine tuning, but is very normal that when adjusted using one source it will be different with another source. It depends on whether the sources are close in color subcarrier frequency or not.

2) At the horizontal sweep rate you are using on your scope, adjust the 3.58 traps for minimum "fuzz" (trace thickness), which is caused by residual 3.58 MHz at the output of the demodulators. You may also be able to see the 3.58 MHz in the picture as a fine, moving dot pattern.

Sometimes when chroma osc lock is effected by fine tuning it is a result of the horizontal hold being set to the edge of lock and the flyback winding pulse that gates the burst isn't lining up with the burst.

I am calling it done. The set has a much better picture, probably not perfect but I am very happy. Maybe related to the full alignment or maybe due to the new to me Blonder Tongue BAVM-860SAW modulator but I no longer get horrible noise during commercials transitions which made it un watchable before. Next will be a final color purity and convergence once I get the set brought into the living room.

A special thank you to old_tv_nut. Your help and advice very much appreciated.

Pictures, please!

Some pictures below to include the Danish modern cabinet and also my test bench setup. As I look close I see some ghosting or smearing, maybe an artifact of the setup and adjustments, also the CRT in the cabinet should be a bit stronger so the guns and contrast can come down.
https://i.imgur.com/0gmldVs.jpg

https://i.imgur.com/A6xS2sT.jpg

https://i.imgur.com/sNXAoFq.jpg

https://i.imgur.com/HfuyFBi.jpg

https://i.imgur.com/iSJkKmi.jpg

https://i.imgur.com/8MaO7cn.jpg

Thanks!