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#46
05-27-2015, 12:49 PM
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Quote:
Look at the boost caps in the Porta-Colors. 
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#47
05-27-2015, 05:26 PM
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Quote:
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#48
05-27-2015, 05:53 PM
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Yeah those CCII CRT's were probably the best rectangular tubes Zenith made. They just keep going and going. The later System 3 CRT's just don't hold up as well. Then you got the 90's ones which die after 2 years.
And for displaying color, The CCII could even give the Merril a run for its money.
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#49
05-28-2015, 06:56 AM
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There are 2 kinds of goo. One the factory put on. Dont
remember which sets but several brands had it. When the sets got older it turned into a filthy mess that we cleaned off & didnt replace. Other sets had aftermarket goo. They came from houses that had a lot of greasy cooking. Covers everything in the HV. You can tell a lot from the crap on a chassis. Example a thin white coating is from a humidifier. A thick white powder is talc & the set is a bedroom set. Can also tell cat or dog, wood stove, smoker etc. A nice thing abt SS sets is the chassii were always cleaner. Some tube jobs had inches of crud that we took out side to blow out. And yes 1970's Zenith delta jugs without question were the best. But in-lines get a bad rap because the delta were so good. More failures but they came in short runs. Example we saw many M1970P with bad tubes at 3 yrs but they all came from one batch of 12 we sold. A call to Zenith got a free tube IF we agreed to not charge labor. Needless to say we only did that for "our" sets... The 90's were different. Those jugs were pure junk. Zenith did extend them up to 5 yrs. The higher end the set was the longer they extended it. 73 Zeno  73 Zeno
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#50
10-11-2015, 04:33 PM
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Ah the joys of demonstrating 50 year old electronics. Got a new problem.
Know how when the TV image first comes up, it's large and dim, but then shrinks to proper size and brightens? Now it's not shrinking or brightening, and adjusting the brightness control makes the image go dark at both ends of the knob's range. So the TV has a large, zoomed in image. It has been sitting I haven't messed with anything on it. What could have happened to it?
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#51
10-11-2015, 04:45 PM
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Bad HV rectifier tube is one possibility, particularly if the picture looks okay otherwise.
Turning the brightness up puts an extra load on the tube, if it's weak it can't supply enough HV and the picture blooms and darkens.
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#53
10-11-2015, 08:15 PM
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No, HV rect tubes can lose emission, resulting in voltage sag under load and 'blooming'. It's a not-uncommon problem.
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#54
10-11-2015, 08:29 PM
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Wouldn't that be a slow process though? This just happened instantly after a few months of sitting unused.
EDIT: decided to reseat the Hv rectifier tube and what I assume is the shunt regulator tube, and now there's no HV. Perhaps i should take a look at those sockets. Last edited by MRX37; 10-11-2015 at 09:17 PM.
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#55
10-11-2015, 09:48 PM
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Black and White TVs DO NOT contain HV regulator tubes or HV regulation.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4
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#56
10-12-2015, 10:14 AM
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Quote:
The set uses a 3AT2, HV rect, 6AL3 damper and a 6JN6 or 6HE5, horiz sweep output. Hopefully, the flyback didn't pick up moisture and short the winding. Motorola flybacks were probably one of the most reliable, but could fail after 50 years. 
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#57
10-12-2015, 10:55 AM
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I have a hunch.
The tube I reseated was not the HV rectifier tube. I learned from working on the Sylvania that the HV rectifier is hidden inside the flyback cage, and sure enough I found it inside the Motorola's flyback cage as well. I pulled it out and one of the pins was coated in goop. So I cleaned it and the socket with contact cleaner and put it back in. Now just waiting for the residual to dry. It's supposed to be non conductive but I always give it an hour to dry to be safe. I'll update this post with the result soon. EDIT: Aaaand... nothing. So where's this voltage doubling cap and how do I measure B+ off it? Last edited by MRX37; 10-12-2015 at 11:30 AM.
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#58
10-12-2015, 07:47 PM
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Quote:
If you look at the tube location diagram, you'll see the terminal points, where the focus taps are. It shows, B+, grnd and boot. Motorola always referred to boost as boot or bootstrap voltage. Be careful, measuring the boost, as I might be 1KV or higher. I wrecked a few meters checking boost voltage. Right now, all you're interested in is the B+ voltage.
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#59
10-12-2015, 08:33 PM
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Lets try and simplify this, well, for me anyway. I'm still very new to tube electronics, and I'm learning as I go. Please bear with me.
Now that I have a decent camera again, here's a full, high resolution shot of the chassis: http://imgur.com/JFDq0nP If you'd be kind enough to point out where I need to put my meter leads, and maybe some other areas where I should test voltages, that'll cut down on the number of stupid questions on my end.
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#60
10-12-2015, 09:06 PM
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See if you can show the TOP of the chassis for me....it will help me to figure it out better.
So far...I THINK...I see where you need to check. Looks like the main filter cap is on the extreme right....partially under the bottom of the cabinet. I only see a BIT of it...and need to see the TOP of the chassis, to tell if there are MORE caps...that need to be checked. Scratch that....I checked an earlier post...and now see the chassis. Last edited by rca2000; 10-12-2015 at 09:09 PM. Reason: more info.
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