Stan,
If I understand your AM setup, you are driving two 8877's with a Viking
Valiant transmitter that has three 6146's. The Valiant has the capability
of around 600 watts pep on AM phone. Is it possible that in your quest to
bring down the driver carrier power that you are still overdriving the amp
on voice peaks?
I run a single 8877 on AM that needs only 14 watts carrier and 60-70 watts
on voice peaks.
73,
Ken W2DTC
----- Original Message -----
From: Stan C.
To: amps@contesting.com
Sent: Sunday, March 28, 2004 1:42 PM
Subject: [Amps] 2x8877 question
Hello gang.
I have a amp running two (2) 3CX1500A7 tubes. It was built to use on 75m
AM. Here is the problem. With it keyed....no modulation....the grid current
is about 40-50 mills. When speaking though the grid current peaks to 200+ on
voice peaks. Using the "load" to bring it down really brings down the
output. I have ran other amps (Alpha 89,Command 2500E,etc) and have had no
problem keeping the grid peaks down by advancing the load. But only loosing
100-200 watts output. The transmitter is a Johnson Valiant.
I am wondering if I increase the bias voltage from the current 8.2 to say
12 or 16 volts if this will help out. I know I will have to drive it a bit
harder to get a given output with the higher bias voltage,but that is no big
deal.
Any help from the knowledgeable would be greatly appreciated.
PS....plate voltage is 3900v under load.
Take care,Stan
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