#16
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So just putting the resistor across the heater will enable the 14atp4 tube to work. Now I'll have to double check to make certain that the measurements are really close or the same. Well it looks like the 12atp4 overall length is around 3/4 of an inch smaller ,bulb diagonal is the same , screen is 12 1/6 x 9 1/2 as opposed to the the 12rp4 is 12 1/8 x 9 5/8 . How does this look, slight mod maybe to fit the same as the other, what would you decide, chance it ? It is very close.
Last edited by timmy; 11-23-2017 at 07:20 PM. |
#17
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I just mentioned a 50 ohm, as it's a more common value and will shunt 7.5 volts, kind of a happy medium. Current in a series circuit is constant and the slight increase will balance out. |
#18
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Timmy as far as the ATP4 crt fitment you will have to try it to see, we can't do it for you it's up to you to try it and go from there. Dieseljeep bud you and I, both got the resistance value wrong for the tube in question 8.4 volts not 6.3 volts makes the resistor a 56 ohm not 42 or 24 ohm. 3 watt rating still is fine. Went back and checked the tube specs again and saw the mistake, sorry about that. Tom.J
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#19
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#20
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Yes you could, finding room on the chassis mite be a bit of trouble though. Finding a transformer with a 8.4 volt at 600ma rating mite be hard though. Remember set makers used shunt resistors all the time till the art of tube making got to the point where their were standardized current draw for all tubes. Tom.J
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Audiokarma |
#21
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In that set, there was enough room to mount the transformer. |
#22
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Well if I go with a transformer I have to find at least an 8 volt 4 - 8 ma which may be hard to find.
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#23
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It's not like you're dealing with a 3KP4. |
#24
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I have an odd question, how does putting a resistor across the 6.3 heater source give 8.4 v and more ma ?
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#25
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An odd question, how does placing a resistor across 6.3 v heater source give 8.4 v with higher ma ?
Don't know why it posted twice.... |
Audiokarma |
#26
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Once in a while, an experiment is in order! When installing the CRT, try various resistor values between 42 and 56 ohms and check the voltage across the heater. Line voltages vary in some areas. Get the set working properly first, with the original CRT and then address the CRT issue. |
#27
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Last edited by timmy; 11-25-2017 at 03:04 PM. |
#28
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Parallel heater circuits are constant-voltage So in a series string, the tubes' heaters have to be rated for a constant current. Therefore different voltages appear across different heaters, leading to oddball voltage designations (e.g., 2AF4, 3CB6, 5GH8, 19AU4, etc. etc.) In a parallel circuit, the heaters all have the same voltage but some have different currents. |
#29
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Ok so this admiral is recapped and have sound and close to 9kv for hv and the b+ is around 10 volts less then it should be however I have no raster at all the video tube tests good, any ideas .
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#30
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Is your current tube meant to use an ion trap, and if so is it on and adjusted properly?
What are your gun voltages and what does the service manual say they should be? Those are the first questions I'd ask myself in your shoes.
__________________
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 |
Audiokarma |
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