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#1
03-30-2013, 03:53 PM
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What's the need for an ion trap on an aluminized picture tube
I was looking at something and got off track and found a flier online for Sylvania aluminized picture tubes, and then again for rca aluminized picture tubes, with cross reference numbers, and a table with notes. In the notes table listed the need for an ion trap on the replacement tube, which was a new aluminized picture tube. Wikipedia says that ion traps were not needed on the new aluminized picture tubes. So can some of you who know the real poop on this please post your story on the topic. Thanks.....
From Wikipedia: "" Devices known as ion traps were used in early television receivers, prior to the introduction of aluminized CRT faces in approximately 1958. The ion trap must be delicately adjusted for maximum brightness.[8][9] The purpose of these devices was to prevent ions from discoloring the phosphor screen.[10] [edit] "" I thought this was correct.
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Yes you can call me "Squirrel boy" Last edited by Username1; 03-30-2013 at 03:57 PM. 
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#2
03-30-2013, 05:48 PM
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If they used an angled gun assembly when manufacturing the tube, then you'd need the ion trap magnet regardless of whether or not the tube was aluminzed. It's possible that Sylvania simply decided to use their existing stock when manufacturing the aluminized tube. Why manufacture straight guns when you already have gun assemblies that will work?
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#3
03-30-2013, 06:10 PM
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Economics....... Ok, thank you. So While the aluminum protected the screen, the gun design dictated the use of the trap. Did they then change numbers, or suffixes when moving to a non ion trap tube, or did they rely on the tv tech noticing the shape of the gun to know when to use the trap when replacing the tube...? Of course most likely the box may have has a note tag as well.... I know the shape is quite pronounced, as far as the bend goes.
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Yes you can call me "Squirrel boy"
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#5
03-30-2013, 06:25 PM
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Simply aluminizing a tube could have resulted in a suffix letter being attached to a preexisting tube number. For example, a 12LP4A, when aluminized, is a 12LP4C. Same gun; one is aluminzed with a grey filter faceplate, while the other is not aluminized with the grey filter faceplate.
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#6
03-30-2013, 07:44 PM
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yah, that's where I began this thing.... My brother gave me a tv with a 12LP4 and a brightner on it. It needs to be recapped but I'm looking into what the difference is with the aluminum tube which from what I have seen is the "A" suffix. But I may be wrong, have not looked into it that seriously yet, figured I'd get it working first. 12KP4 is aluminized too.
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Yes you can call me "Squirrel boy" Last edited by Username1; 03-30-2013 at 07:52 PM.
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#7
03-30-2013, 08:12 PM
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This website has data sheets for many tubes, including CRTs:
http://tubedata.milbert.com/index.html The sheets make it easy to compare specs for 12LP4/A/C, etc. Regards, Phil Nelson Phil's Old Radios http://antiqueradio.org/index.html
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#8
03-30-2013, 08:36 PM
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The 12LP4A just has a grey filter faceplate; it's not aluminized. The 12LP4C is, as is the 12KP4 as you mentioned. The 12KP4 shouldn't require an ion trap. Now rebuilders have made things a bit murky. Some rebuilders aluminized tubes, and I would venture to guess that some probably rebuilt 12KP4s with angled guns if that is what they had on hand at the moment. At the end of the day it doesn't really matter what the number on the tube is. If it uses an angled gun, use a trap. If not, leave it off.
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#9
03-31-2013, 03:24 PM
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Quote:
The 12KP4 is an aluminized CRT with a clear faceplate. The 12KP4A is aluminized too, but here the 'A' indicates a 65% transmission gray faceplate. For most other CRTS of this period, the 'A' indicates an alumin9ized CRT. Go figure. 
Last edited by cbenham; 03-31-2013 at 03:26 PM. Reason: Clarity
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