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#1
04-06-2003, 04:30 PM
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kcs 47a doorknob cap
recapped this thing last year. just now getting back to it.
fired the set up and it had a dim out of focus picture. was only getting 8,000 volts to anode. removed the doorknob cap. it was hot. now a i have a bright picture. do i need to replace this or just leave it out. i also have no audio any pointers on this chassis. thanks steve 
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#2
04-06-2003, 04:56 PM
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Steve,
You won't hurt anything but possibly picture quality by leaving that doorknob cap out of the HV circuit. I'd replace it if it was my set. I gather you have a metal shell CRT? I have some sets with that chassis but little experience on the bench with them yet. Can't help with the audio question. Rob
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#3
04-09-2003, 03:36 PM
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Doorknob cap
In all-glass CRTs, the internal 2nd anode coating in combination with the grounded external aquadag coating form a high voltage cap to ground, about 500 pF. This filters the rectified output of the 1B3 (half-wave DC pulses at 15,734 KHz) to steady DC.
In a metal shell CRT, there is no "capacitor", so a 500 pF doorknob was added externally to perform the filtering function. Leaving it out is similar to leaving out an electrolytic in the B+ supply, although the "hum" produced will be at H frequency and will affect only the CRT. Last edited by wvsaz; 04-09-2003 at 03:44 PM.
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