[Amps] 8877 Plate Voltage

[Jim W7RY]

It will be VERY EASY to drive at this voltage.  Probably around 25 watts for 
1500 out if it’s a good tube. I'm thinking of putting a 3 or 4 dB attenuator 
into the input to get the drive up to around 70 watts or so. Mine runs 4100 
volts no load.

73 and good luck!
Jim W7RY


-----Original Message----- 
From: Charles Bibb
Sent: Saturday, June 30, 2012 2:33 PM
To: amps at contesting.com
Subject: [Amps] 8877 Plate Voltage


Starting a new project.

I'm collecting parts for a new HB 8877 amp.  One really nice part
that I've recently acquired is a massive transformer for the HV
supply.  This transformer came out of a commercial FM transmitter
that ran an 8877 at 1 kw continuous duty.

While that power supply used a choke-input filter in the HV supply, I
want to run the higher voltage obtained by a cap.-input filter. With
a cap.-input filter, however, the HV supply will be a tad over
4150VDC, using the "best" primary taps available. Can wire for
higher, but not any lower.

My question(s) is/are:  How critical is Eimac's "absolute maximum
ratings" as far as plate voltage is concerned.  I know that under
load, with acceptably regulation, the plate voltage will be about
where I want it at 3800V.  Is the slightly-too-high potential on the
anode under no-load a problem? Or, should I just not worry about it
and "let 'er rip, tator chip".

Anyone have experience here?

73,
Charles - K5ZK

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