Gary, a similar question was asked several years ago on amps and I replied
to it with values from some info I have on CRL doorknob ratings. I can't
seem to locate my data but here is my post. My understanding is that the
circulating current in the tuned circuit is about Q times the plate current
and your mod obviously increased the Q a bunch. I think the caps are
overstressed. Here is the link
http://lists.contesting.com/_amps/1999-08/msg00161.html
73, Dan, N5AR
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]On
Behalf Of Gary Schafer
Sent: Thursday, April 12, 2007 9:58 AM
To: amps@contesting.com
Subject: [Amps] Ceramic capacitor ratings
Working on my TMC amp with the pair of 3-500Z finals and the toroid tank
coil. 1.6-18 MHz.
I tried a tank coil for 20 meters that I made out of ¼ inch copper tubing,
2? diameter and 8 turns. I got another 300 watts out of the amp! Efficiency
with that coil is 52% compared to around 38% with the toroid coil.
The amp runs 3000 volts at 700 ma.
Now the question is about ceramic padder capacitors used in the plate tune
circuit. There is a variable plate tune cap that is 23-347 pf that is in
series with two (parallel) ceramic small door knob type caps. The ceramic
caps are 100 pf each for a total of 200 pf in series with the 23-347
variable cap.
The ceramic caps are CRL 850S N750.
I am wondering about the current carrying capacity of these capacitors in
the tank circuit being in series with the variable cap as all the tank
current is going thru those caps. Now with a better tank coil that is more
efficient I would guess that the circulating current is higher than it was
before.
Also will they handle the current in this configuration at higher
frequencies if I try to put the amp on 15 and 10 meters?
Any help appreciated.
Gary K4FMX
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