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GE 805 Focus Coil Question
I just acquired a chassis for the 805 but the bracket for the focus coil mount had been ripped off the yoke surround. It was held by 3 rivets. I repaired and reattached the coil bracket but it required an almost complete disassembly of the coil/yoke bracketing assembly.
I'm taking a different approach to my restorations. Instead of the capacitor shotgun, I'm attempting to do as much as I can to see what's possible on original components where that can be done without risking unobtanium parts. The 805 does not have a power transformer and is series string. I brought it up through the dim bulb steps and I have sound and HV but no light on the screen. The 10BP4 has an ion trap. I think I'm working with 2 variables and that always creates a bunch of possibilities...the position of the focus coil (no original reference since it was removed and a multi position range of motion) and the ion trap. Does anyone have any information specific to the 805 or know of a methodology as to where to start this process of finding the sweet spot for both of these? Or am I wrong and these 2 hardware pieces have nothing to do with one another as far as producing light on the screen? Thanks! Chris |
#2
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They do both have an effect, but I would expect the on trap to have a bigger one. Have you tried moving the ion trap magnet all around, slide up and down the neck and flip it around?
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#3
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Thanks Bob |
#4
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Don't worry about being aggressive. Go 360 and as far up and down as you can. you won't hurt anything. The worst thing you can do is leave it running in the wrong position for long.
The electron beam is hitting internal metal elements in the gun. Eventually, metal will vaporize and reposit elsewhere. Potentially causing a splotch on the screen |
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On a sort of related subject, back before aluminizing, they had to have made many bent beam type CRTs and even some after that were aluminized, so there had to have been many thousands if not even millions of them, and ion traps for each of them, don't the ion traps outlast the tubes they were with? So you would think there would be lots of them out there, but they seem to be rare, as do focus magnets, weird.
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために |
Audiokarma |
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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 |
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"Capacitor Shotgun" sounds suspiciously like a railgun countdown sequencer.
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I have only ever found one aftermarket trap on evil-bay, and this was years ago before I knew that the original one for my 12LP4 was NOT lost in all the moves over the years and was OK, it too was a dual, but seemed way too strong for the tube comparatively, not sure what it's used on, still have it, however.
I still look from time to time out of curiosity, but have not seen any others since. I have heard tell of adjustable ones, but never seen one. ( adjustable gauss )
__________________
=^-^= Yasashii yoru ni hitori utau uta. Asu wa kimi to utaou. Yume no tsubasa ni notte. いとおしい人のために |
Audiokarma |
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I have one but have never used it since I don't know how to set the strength.
They are kind of a pain to storage and organize. They stick together which may effect strength over time. I image most were tossed along with the sets. |
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I would check voltages at the base of the crt, cathode, grid 1 and grid 2 and compare to values on the sams schematic.
jr |
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If the chassis is biasing it hard into cutoff you could stick a straight gun aluminized tube in there and it'd still be dark.
__________________
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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The Sams gives voltages for the 12” version but I used them as a reference anyway. The cathode is supposed to be 365v DC and I’ve got 345v. G2 should be 100v and I’ve got 210v. When I was fishing to see if I could find a place to check G1, I found a 0.1uf cap connected between the lead going to the CRT and a coil had broken off of its solder tab. Of course at that moment I had to go upstairs and shut down for the night but I’m hoping that solves the issue. We’ll see. I wonder if the loss of that cap in the circuit could have led to the G2 voltage doubling?
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Audiokarma |
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