Ion Traps
 

I found I am having an ion trap problem with my current 630ts restoration. Rather than jump into the problem and ask for help in solving it I thought I would ask what it is that the ion trap does exactly. Why do some sets have permanent magnets, while others have electromagnets, and some have both?

The earlier sets used Electromagnets, the 621, 630, 721 (some) later sets used PM traps. None should have both, possibly you are seeing the Focus Coil that is around the neck of some earlier sets?

Early tubes, before Aluminization, had the Electron Gun mounted at an angle so the Ions wouldn't hit the screen and burn the Phosphors.

Since Electrons are affected by magnets but Ions are not they used the trap to pull the electron beam back in a straight line so it would reach the screen, the Ions simply hit the neck of the tube and do no harm.

You can replace an Electromagnetic trap with a PM type but on the 630 I think the trap is part of another circuit, if it has an open coil it may be a problem.

If your trap isn't working I think it's fed through one of the large resistors in the black box on the rear apron, an open resistor means a non functional trap.

A 10BP4 uses a double trap, you'll notice the 630 trap has a large and small coil, the smaller one faces the front of the set,
if it were a PM trap the same thing applies, smaller magnet to the front.

The correct adjustment for an ion trap is to simply slide it side to side and back and forth until you have the brightest raster and good focus with no neck shadows. There's usually some interaction with the Focus adjustment so you may have to go back and forth between them.

Thanks for the concise response. I'm hoping these threads will be helpful to others who might have questions like these but are afraid to ask.
Regarding a set using both types of ion traps. My RCA 730tv1 has both types of trap on it. When I was writing about it's restoration there were a lot of people who said that doesn't make sense, but it definitely needed both traps for the best picture. Remembering my experience with that set I thought I would try adding a pm trap to my 630. The difference is night and day. I just can't get enough brightness out of the 10BP4 with the electromagnet alone.

Here is a picture with only the electromagnet trap. This was the brightest I could get after much adjustment.

http://farm9.staticflickr.com/8501/8...708f6f55c9.jpg

Here is a picture with both traps. The brightness control was not changed between these two pictures. The ambient light was also not changed even though it looks like it was. The only thing I adjusted was horizontal and vertical centering as the pm trap pulled the beam at a different angle.

http://farm9.staticflickr.com/8497/8...2cdfa97852.jpg

What would account for the original trap not being able to get maximum brightness out of the 10BP4?

Perhaps there's not enough current flowing through the original trap ? Have you checked the various resistors and voltages attached to it ?

The same thing occured to me last night as I was thinking about it. Seems pretty obvious now-
"What would account for the original trap not being able to get maximum brightness out of the 10BP4?"
The fact that it isn't working properly :withstpd:.
It seems like a lot of us are working on 630ts' at the moment. Is any one capable of giving me some reference measurements?
I've got -92V on the green side of the focus coil with the focus control set for the sharpest focus, -67V on the yellow side of my focus coil, -56v on the red side of my ion trap, and on the other side of the bleeder resistor, where the schematic shows -18V, I have -21V.

http://farm9.staticflickr.com/8091/8...10f7bc5340.jpg

My 185A section of the bleeder resistor is off from spec. I have a different version of the bleeder resistor in my set, it is only 160ohm instead of 230ohm. That puts it off by more than 20% so perhaps my problem is that resistor.

HI All;
VTS1134, Have you also tried to rotate the trap once you have some picture.. Not the back and forth or front to back, that you have at the present.. But, once it shows a picture, then turn it on the neck of the tube going round and round slowly at that same position, looking for a better picture.. You may have it in the correct front to back position, but not the correct in relation to what the gun needs for full output. My clue is the cuttoff of the picture.. Now it may also, be low current in the coil, as well.. One possibility would be to disconnect one wire and wire in an Amp Meter and see what the figure actually is.. And using Ohms Law see how close it is to what it needs to be.. Check what the Schematic shows and what you actually have on your set for its values.. And compare them.. Since on the Schematic you have the Resistance and the voltage drop, you could figure the current flow.. I am not ready to power my set up as of yet.. Maybe Bob Could help, yet from His Video He is not that far along either..
THANK YOU Marty

Well yeah, that would also result in higher-than-called-for current thru the entire series string which includes the focus coil (you were having trouble with the focus being out of range earlier, per your PMs). Try tacking some more resistance in series with R185 to bring it up closer to the called-for value.

To expand a bit on Eric's excellent synopsis, think of winnowing wheat for an analogy. The wind separates the light stuff, the chaff, from the falling grain which is much heavier.
In the CRT with the crooked gun, the the entire stream is directed off-center so the heavy stuff (the ions) is dumped harmlessly aside, while the light stuff (the electrons) are deflected back down the center of the tube. The magnet is actually an 'electron beam re-directer'.

Ions, being charged atoms, actually are affected by magnets, but far less so than electrons which are much lighter and easier to deflect (per the analogy).
For all practical purposes here, the ions are not deflected enuff to matter.

I couldn't say it better...

Hi All;
VTS1134, It may or may not help, but here is a video from B Andersen, while adjusting for correct Ion Trap placement..
http://www.youtube.com/watch?v=Ax-zTvlT59M
THANK YOU Marty

Am I correct in thinking that according to the schematic I posted above I should be able to read 36 ohms across the ion trap when the 56 ohm resistor is removed across it and it?

Yup. That's provided the two coils possess the correct values. But first disconnect one end of the ion trap to take the measurement (to prevent other circuit resistances from messing with the reading).

Hi All;
VTS1134, Yes, But if you look at Bob's latest video, without taking it out, the 56 ohm resistor, He got about 22.4 ohms on his Ion Trap Coil.. Yours might not be the same but, it should be close..
http://www.youtube.com/watch?v=arlJTCAbvRE
THANK YOU Marty

Problem solved. My ion trap is open :dammit:. I'll have to start searching for a replacement.

Hi All;
VTS1134, As I see it You have three choices.. 1. See If you can fix your ion coil(s), it might be a bad connecting wire, also, look and see If you see any burn spots and see If its fixable.. 2. put a resistor in its place and use a Permament Magnet instead.. 3. find another one like the Bad ion coil, only not bad..
THANK YOU marty