Hi Bill,
Well, I experimented long and hard, testing even high-grade xmitting
ceramics in the plate tuning and loading locations. They all drifted to an
unacceptable degree. I presume from the tube heat alone.
So, have sworn them all off. Big micas rated 8-amps do the trick. They don't
budge one iota! Lesser current ratings are OK in the loading section, but
still need to be micas.
Good investigating & 73, K6XK
-----Original Message-----
From: WB6WCW@aol.com <WB6WCW@aol.com>
To: royanjoy@ncn.net <royanjoy@ncn.net>
To: <amps@contesting.com>
Date: Saturday, January 23, 1999 7:26 PM
Subject: Re: [AMPS] To Ten-Tec Inc, et al, Re: Titan II
>Hi Roy:
>
>My experience in fixing-up an Amp Supply LK-550,
>which uses (3) 3-500Z tubes, is that the 'padding'
>capacitors get quite hot on 80 and 160.
>
>I believe it is due more to a misuse of the parts, than the fact
>that they are ceramics.
>
>If you look at <http://www.rfparts.com>, under "Products", look
>at "Ceramic Bathtub" capacitors. It lists the current ratings
>of the HT-50/HH58/850S family of capacitors. At 1 MHz, the
>1000 pf caps are only good for 1.6 amps (and they do overheat).
>
>If you replace the 1000 pf with a pair of 500 pf caps, then the current
>rating is 6.4 amps (and will not overheat). Carl (KM1H) recommended
>that I use 750 pf units, it would require less parts (cheaper), but haven't
>been able to find any of them.....
>
>After fixing all of the "Tune" padding capacitors, I still had a problem
>on 160 mtrs with the ceramics they used on the output side of the
>pi-network. Same problem; 1000 pf capacitors overheating. Am
>presently replacing them with 500 pf units-----and I sure hope that
>solves the final problem (it's getting rather expensive).
>
>Good Luck & 73's
>
>Bill W6WCW (E-Mail: WB6WCW@aol.com)
>Santa Barbara, CA.
>
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