[Amps] power limiting in 8410 amps?

[Jim Thomson]

Date: Tue, 6 Nov 2018 21:23:38 +1030
From: "Leigh Turner" <invertech at frontierisp.net.au>
To: "'Steve Bookout'" <steve at nr4m.com>
Cc: "'AMPS'" <amps at contesting.com>
Subject: Re: [Amps] power limiting in 8410 amps?

<Yes I concur with this suggestion Steve.

<With only 200 Volts on the screen in AB1 linear mode the 4CX1500B tubes are
<likely being starved and held back like variously reported amongst 8410 amp
<users. The screen voltage probably ought to be up around 275 to 300 Volts to
<ensure unconstrained power output to 1500W+ without significant gain
<compression.

<Leigh
<VK5KLT

## What is the IMD on this amp, when  driven to 1.5 kw pep out...
with a 2 tone signal ??   It cant be good. 

##  Baffles me why Alpha   even used a pair of 4CX-1500Bs. 
They should have stuck with a single  8877.... like their auto tune 9500 amp.
IE: a manual tune version of the Alpha 9500.  

##  By using 2 x 4CX-1500Bs.. they have just complicated it needlessly. 
2  sockets, 2 tubes, 2  chimneys, 2  anode connectors,  2  parasitic suppressors,
regulated screen supply, bias supply, etc, etc.  Talk about making a simple
manual tune  amp into an  expensive exercise. 

##  A  single 8877  would have easily sufficed, reliable, proven, etc.
At least  OM power got it right with their  OM-4000.. which uses the
chinese version of the tube. 

Jim   VE7RF