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#61
10-07-2010, 06:35 PM
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Well I'm all the way in South Florida, West Palm Beach to be exact... If your in IL we are far apart... It would be nice if there was one local from me, but i seriously doubt it..
Nothing has been done to this set other than cleaning, so everything is working off original parts even all the caps, transistors etc. may have been serviced in it's life time so a few components may have been replaced at one time.. I don't know how the caps hold up or if needing to be recapped.. Last edited by tvcollector; 10-07-2010 at 06:52 PM. 
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#62
10-07-2010, 09:24 PM
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Yep, in IL as my location says. Well, good to see that set running, anyway. It has some unique chroma circuits developed by Motorola's Chief Scientist at the time, Norm Parker.
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#63
10-09-2010, 01:19 PM
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I received my Sencore CR70. I've been testing and did a little bit of restoration. Now when i do the Emissions test it reads good or bad depending on the setting of the cutoff control.. All the way down is bad, in the middle (up/Down) reads into the lower part of good, and all the way up reads in the middle part of good.. I did the auto restore and then the manual 1 restore. I don't see much of a different in the picture.. The shorts test reads good, tracking also reads good.. any input would be appreciated.
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#64
10-09-2010, 03:21 PM
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I'd love to hear more about those chroma circuits, old_tv_nut... Stories like those, about yesteryear's innovations, always fascinate me.
BTW, that's a great set.... Don't think the c.r.t. looks half bad, to be honest.
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#67
10-09-2010, 08:27 PM
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ok that was something i was not doing, i must have missed that part in the manual. I did this test on a 1976 Sanyo set that has a not so bright picture that look to be the green is a little too much, but the test on all three guns passed very good, and the cut off is set in the range with the knob three quarters of the way to get to the cutoff range, which i don't know if that means anything. I'm guessing more than likely there are problems in the circuit on this TV and the Motorola Quasar. I also tried the Motorola Quasar again setting the cut off and all three guns are well into the good range, with the cutoff setting with the knob being pass three quarters of the way..
Last edited by tvcollector; 10-09-2010 at 08:37 PM.
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#69
10-10-2010, 06:03 AM
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Well i hope the tester is working properly, i spent $125 on it and that was the as is price
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#70
10-10-2010, 08:22 AM
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as long as you can get the cut off in the range you are good to go, regardless of the setting. Sounds like your CRT is fine, I would not recommend any more rejuv attempts to make anything better.
As others have said, a CRT can test very poorly and still produce a watchable pic, no doubt less than perfect, but there are a lot of adjustments that can be set to make a otherwise weak tube look ok. case in point, a zenith I picked up some time ago, it had a tube brightner on it which I removed, the red gun is weak. However after a few minutes the red picks up so its important to let things warm up before any adjustments. Second adj drives and screens you can compensate to some degree for diff in guns, tracking may not be great but if you are not fiddling with the brighness then it really does not mater, set it up for a low light level and leave it there. Dont for get to set the focus, again it is optimized for the brightness setting. bottom line is if one gun is weak It can look ok, not great but ok. But it sounds like your CRT is not bad.
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#71
10-10-2010, 05:51 PM
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I've tested two other sets.
My 1980 Quasar which when i brought home had a bright red picture. I had adjusted the levels to get a equal grayscale. Now i just did a test on it, the meter in the emissions test went into the good, but than slowly went into about three quarters of the way into the bad. Now i tested each gun and all were equally in the same bad range. I've noticed that when testing 4 others, the meter barley moves (or not at all) when testing each gun. I did a manual restore and all three guns are now in the middle good. I did color tracking and both shorts and all are good. I plugged in the set and was thinking ok the tube was restored a little now, so now when i see the picture the colors will be off and I'll probably have to adjust the red, green and blue on the picture tube circuit board to equal to a rejuvenated tube. Tv came on and the pictured looked the same.. Set two is a portable 1978 Panasonic. Which also has the same problem with the color. This one i tried to adjust the equal the grayscale and can't. But the bright picture looks good on this set, but when i turn down the bright the picture becomes a blue tent. I just now tested the tube and everything is well into the good range. Now question is? is my CR70 working right? or more than likely on the 70's and 80s model sets the circuits begin faltering most of the time and not the picture tube? Last edited by tvcollector; 10-10-2010 at 05:55 PM.
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#72
10-10-2010, 07:40 PM
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Quote:
One of Norm Parker's inventions was the idea of directly demodulating the composite video (containing luma with chroma subcarrier riding on it) into red, green, or blue. Now, you can't do this correctly without some manipulation, because, unlike the RCA dot-seqential system, the NTSC subcarrier has the wrong amplitudes of R-Y, G-Y and B-Y components. In the NTSC transmitter, B-Y is divided by 2.03 and R-Y is divided by 1.14 before modulating the subcarrier (actually, the equivalent factors are in the formulas for the I and Q signals). Also, the luma signal consists of .3 R + .59G + .11B instead of .33 R + .33 G + .33 B as they are for dot sequential. So, direct demodulation gets the colors wrong. It's necessary to adjust the amount of chroma signal going into each color channel. R-Y needs a boost, B-Y needs an even stronger boost, and there is too much G-Y, (because there's already a lot of G in the luma) so G-Y needs attenuation. What Moto did in these discrete diode demods is to make the luma be a common-mode signal for three demods, and the chroma a differential mode, with the required amplitude for each. So, all three demods have their required chroma floating up and down on the luma signal. At the output of the demods you now have the sum of luma and a demodulated color difference, that is, each one puts out R, G, or B directly. When they later went to an IC demod, they used the same principle to put a luma current in common mode into the bottom of each differential mode chroma demod, getting R, G, and B as outputs. Norm also patented a method to restore the upper I sideband before demodulating on the R-Y, G-Y, and B-Y axes, but this was deemed too complex to put in a set design, especially before ICs. So, the set ended up with equiband direct R,G,B demods. By the way, when I say "Norm invented" I mean that he developed the theory and some ideas of implementation, but there were others who worked on various ways to realize the implied functions. Edit: fixed the B-Y and R-Y factors (had them reversed)
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#73
10-12-2010, 03:02 PM
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Gees, no one has any input on my last post?
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#74
10-12-2010, 03:22 PM
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difficult to compare the results of tests on 2 different crt's
for what it is worth, i have never been a fan of crt testers and cleaning/rejuv for any color crt - just too many variables - delta gun/inline/age of tube/ et cetera it is usually pretty obvious when a color crt is reaching the end of its usefulness - many b/w crt will test poorly and display a very nice pic - same with color crt's and for what it is worth - i am a believer that if you tested a single crt with five different crt testers you would come up with 5 different sets of readings the last set of pics. you posted looked good - can you post some screen shots?
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#75
10-12-2010, 04:12 PM
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My opinion:
1) If the tracking is good, it's good, although the tube may be on the weak side 2) If the tube tests good, it's good, although the tracking (cutoff or G2's) in your set may be misadjusted (causing blue shadows) Now, if you got a set where one gun could not be adjusted and it tested different from the others, your tester would be telling you that the problem was the tube and not the adjustment. You don't have that in either case you mentioned. For case (1) you just have a warning that the tube that is giving acceptable tracking now may be on the way out, but there is no need to panic until you see some degradation in the picture. For case (2) you are seeing that the tube is probably just fine and therefore you should look for your problem in the circuitry.
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