#16
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These are probably the most important things you can do before you get into modifying the circuit design.... But what if you wanted more protection? Electrically transformers are made up of a pure inductance component and a resistive component, It's the resistive component that ends up getting hot. It's the inefficient part of the wire we can't do anything about inside the flyback.... I'm wondering, If you wanted to shave an extra 20ma. off the current running through the flyback, could ya do it be adding possibly 2 - 10 Ohm, @ 10 to 20 watt wire wound resistor to the horizontal output cathode circuit, and possibly shift some of that heat to the resistor and away from the transformer....? Anyone with one of these sets on the bench willing to test it ? Naturally, you would have to be sure it didn't cause any width problems... Etc.... Not sure if it should be in the cathode circuit, or on the business winding on the flyback supply, probably not too smart to put in in there on the plate cap end.... Maybe on the other side of that..... I don't have a schematic for that set, so can't come up with the exact point..... Anyway, my thinking is, if the resistive component in the flyback "primary" is say 20 Ohms, and you add a 5 Ohm resistor, will you shift enough heat off the transformer to have it not melt the wax....? And still not effect the rest of the set materially.....? .
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Yes you can call me "Squirrel boy" |
#17
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I was also thinking of putting a small computer fan on the top of the HV cage in my 1954 CTC2B, 21CT55 21 inch color. I don't see where it would cause any harm. Yes, I have always thought that around 210 ma was about the max that the cathode current should be at. The HV cage on that old set is completely enclosed except for a hole in the top with a "chimney cap", in which I could install a fan. Possibly the reason that HV cages as so tightly enclosed it to reduce x-radiation. |
#18
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Brian USN RET (Avionics / Cal) CET- Consumer Repair and Avionics ('88) "Capacitor Cosmetologist since '79" When fuses go to work, they quit! |
#19
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Several Hundred Ohms and you strongly change what the meter is actually reading. Most good meter movements are Micro-Ampers full scale, so reading 200Ma, the current handling resistor should be pretty small. For a current reading meter to be highest in accuracy, it would have to present as close to zero resistance to the circuit as possible..... Just as in measuring voltage, the meter should present as close as possible to infinite resistance as possible to the circuit.... That is why VTVM's and digital's are choice for a lot of really accurate DC voltage use especially, because of high resistance on input... .
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Yes you can call me "Squirrel boy" Last edited by Username1; 11-19-2015 at 05:23 PM. |
#20
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http://www.americanradiohistory.com/...-Page-0084.pdf What is your rationale? I know theirs - to prevent the inductive load of the meter from becoming resonant - hence, they shunt it with a bypass cap to ground, effectively eliminating the possibility. My Save the Flyback tester has a .47uf/600V across the meter Your #39 lamp tester was in a May, 1970 Radio Electronics article - they show how to build an efficiency tester, using the #39 bulb. My EBY tester used a #44, and was able to forgo the odd lamp.
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Brian USN RET (Avionics / Cal) CET- Consumer Repair and Avionics ('88) "Capacitor Cosmetologist since '79" When fuses go to work, they quit! |
Audiokarma |
#21
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If it's a good meter - the movement is far removed from the circuit, but the cap
is most likely insurance so no sharp spike makes it to the movement.... A spike that may occur if one lead is accidentally lifted while the tv is on.... It's unlikely the movement's inductance comes into play as it is bypassed by a resistor of small value, 1 -2 Ohms, and then further hidden in a series resistor network.... But I can see that the possibility of the high frequency and unknown internal components to the meter could cause resonance and effect the accuracy of the reading.... So Yes I can agree on the resonance possibility.... .
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Yes you can call me "Squirrel boy" Last edited by Username1; 11-19-2015 at 06:18 PM. |
#22
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So having a cap across it is fine as a 'feel good' measure, but no actual need for it. The movement is gonna 'see' raw, unfiltered spikey waveforms anyway when the instrument is measuring voltage, and is none the worse off for it. |
#23
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A little cooling can't hurt, if you don't mind the noise. I tried a little fan inside the back of my Predicta barberpole set, but quickly took it out because the noise bugged me.
Also, air carries dust, so the more air you force through an interior, the more dirt that may accumulate. I remember cleaning out old desktop computers that were plugged almost solid with dust bunnies. Those computers probably ran for more hours per day than the typical color roundie, however. Phil Nelson |
#24
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Last edited by andy; 11-20-2021 at 03:22 PM. |
#25
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OK I am confused. What else is new. Are there two threads on this ctc 16? Did Tom replace the power supply electrolytic caps? If not I would start there. A quick check would be to hook up a dvd to the set. Put it on pause and see if there is a slight wave in the picture. If you want to use the set as every day watcher, They should be replaced any way. The fly will get hot with the 3a3 sitting on top of it but you should not see wax dripping out of it. Your test pattern is really cool. Must make it a lot easier to do convergence
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Audiokarma |
#26
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The original flyback got wiped out shortly after the set was restored, and I did not want to chance that the UBER RARE replacement would get fried. So I added the fan and the flyback runs cool to the touch now.
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Vacuum tubes are used in Wisconsin to help heat your house. New Web Site under developement ME http://AntiqueTvGuy.com |
#27
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AC at the outlet the set plugs into here with it on is 117VAC. I will look for a high line voltage primary tap on the transformer. My thoughts on adding a fan are that one should add a Heppa filter in the air intake to limit dust intake.
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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 |
#28
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#29
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I use thermal joint compound or grease to aid in heat transfer from transformer frame to TV chassis.
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"You want it WHEN?" |
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