On 07/15/2018 10:20 AM, Bill Turner wrote:
I'm thinking
about replacing the two burned resistors with a single 22 ohm 5 Watt metal
film resistor, and trimming the inductor to a single turn. Does this seem a
reasonable change? Does the tube require any parasitic suppressor at all?
REPLY:
Many amps have parasitic suppressors but actually don't heed them at
all, especially if the leads from anode to RF choke and tune cap are
very short. I would try the amp without the suppressor, bringing up
the plate voltage slowly in class AB mode and see if you get lucky. I
have built several amps using an 8877 on HF ( not VHF) without a
suppressor and all were perfectly stable.
I suspect many commercial manufacturers put in a suppressor "just in
case" or because customers want to see one there.
Most broadcast transmitters that I have see or have downloaded the IB
for have not used any parasitic suppressor at all.
The biggest reason to use any parasitic suppressor is because it is a
multi-band amplifier. (on some bands the design is wrong)
In a single band amplifier correctly designed and implemented ovoids
the necessity for any parasitic suppressor at all.
--
Ron KA4INM - Youvan's corollary:
Every action results in unwanted side effects.
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