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#46
03-06-2015, 10:41 AM
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ok so all caps are changed and also the lytics except the 5- 6kv caps as i clipped one by one to see if this was the problem and it still is not right. and now i changed the seleniums to silicon diodes and a dropping resistor in place but i still have the same thing where once the tubes light and things start to conduct the voltages are jumping up and down and i have no clue why. it seems as if something is preventing the voltage from advancing. unless i need to put the 5- 6kv caps in and this is the problem but still waiting for just radios .
Last edited by timmy; 03-06-2015 at 11:52 AM. 
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#47
03-06-2015, 06:33 PM
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just disregard the last post the 6kv caps came in today and i got a raster and 4kv of hv, and should be higher but its in a really fast verticle roll that if i adjust the vert hold and vert size i can get it to stop for a second then goes nuts again and the vert hold has to be turned to max at one end to get it to stop rolling for only the moment. so i guess ill be looking for resistors in that circuit . theres one resistor off the vert hold checks good and there is another of the vert size and thats good as well.
Last edited by timmy; 03-06-2015 at 07:23 PM.
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#48
03-07-2015, 10:28 AM
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ok here comes the problems , i got a picture but from left to right i have 3 images and the verticle and vert size are not good cant get the full screen without it rolling so bad that it almost goes to a line across. and the brightness cannot be up all the way it gets dim and brightens up alittle if i turn it down.
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#49
03-08-2015, 07:56 PM
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ok the horizontal is fixed now got a single image. now im trying to find 8-9 volts of ac to isolate the heater in the crt to see if its any good it is very dim and the bright pot is fine the hv is 5kv any resistors at the brightness pot or around i checked and are good. i figure this is the only way i can see if the crt is good by adding a few more volts to see if it brightens because there is 6.6 volts at the crt now so 8-9 volts should show something or at least give me an idea. this series string filiment, by taking the crt out of the string i should be able to twist them together just for a test as the heater voltage will rise from the crt out of the string.
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#52
03-09-2015, 08:02 AM
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This brings up a good question, is there a tester that came with the connector to test a 7JP4? Or does one have to use a clip lead connector? I have four different crt testers and not one of them even lists this crt.
Gregb
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#53
03-09-2015, 10:33 AM
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I have one from Eico that will test them. But like most members, it's easier to test in a known working chassis.
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#54
03-09-2015, 11:09 AM
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no there is no adapter for this tube there are voltages said that the tube needs to test accurately and should be done with a tester that lists that tube. i applied 9 volts ac to the heater and was not really any difference in brightness so now im going back to the chassis to look for another culprit like in the video output section, matbe something there like a resistor went up in value. if the tube was that bad at 6.6 vac then 9 vac should have brightened it up noticeably but didnt.
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#56
03-09-2015, 02:49 PM
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Quote:
Gregb
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#57
03-09-2015, 03:15 PM
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Precision CR-30, Sencore CR-70 & CR-7000 and a Beltron (not sure of the exact model #).
Those will only test emissions though. Electrostatic CRTs do not use an ion trap and the phosphor can get dim from ion bombardment even though emissions are good. Operating in a working set is really the best test.
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#58
03-09-2015, 06:51 PM
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well i got the chassis going and i have 2- 7jp4 crts 1 rca and a sylvania. the rca has a clear picture but is very dim and the sylvania is so silvery i cant get much of a picture maybe if i lower the bright almost all the way ill be able to see it, washed out. hv is 5 kv and voltages at the video out tube are perfect and i applied 9 volts to the rca crt and didnt get any brighter so maybe they are gassey, they are old. i clipped one wire from the crt heater and completed the string circuit while trying the 9 volts ac. so i guess if everything checks out within the operating circuit then i guess its safe to say these crts are done.
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sorry 1 is upside down.
Linear Mode
