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Old 02-03-2015, 04:28 PM
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timmy timmy is offline
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crt heater filiment weld

i have a 21fbp22 crt with the green gun heater intermittently works so i found that the heater has 2 extremely thin wires that are the filiments connected to 2 legs and one looks like the factory weld of one wire is touching but no longer welded to the leg or just let go but when its not and tap the neck it sparks blue and makes contact and works. but is there a way to fuse this filiment wire with an arc of some kind without burning that wire to the point of not making a connection.
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Old 02-03-2015, 04:41 PM
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There's not really any sure way of fixing it. Some testers had a weld function, I think it just puts a higher voltage on the heaters while you tap the neck and get it to arc and hopefully stick together, it will never be reliable though.

I had a Portacolor set with he same problem.
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Old 02-03-2015, 05:21 PM
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I don't think it is safe to try welding a single heater of a multiple heater CRT at a meaningful weld voltage... On black and white CRTs one could put a capacitor charged to 200V (which would not hold enough charge to burn out the heater once it welded) across the heater pins....But you can't do that on a color CRT since the heaters are wired in parallel, and would discharge the cap the instant it is connected, and a constant HV supply would burn out the two good filaments.

The best thing I can think of is to supply the heaters voltage through a variable DC supply, and slowly increase the heater voltage to around 8-18Vdc (as much as you are comfortable applying*) before hitting the neck. The heaters can only take so much over voltage for so long, and AC strains the heaters more....Also you CAN'T weld WITH AC.
*More is better, but too much will burn out the other heaters.
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Old 02-03-2015, 05:52 PM
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A 6.3 heater can usually take 12 volts for a while (The Beltron restorer requires 10 volts on the heaters) but the cathode might be damaged at those temperatures, also banging on the neck while the heater is that stressed is probably not a good idea.
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Old 02-03-2015, 08:25 PM
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No sure way to fix it, besides rebuilding.
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