[Amps] TL922 efficiency

[Jim Thomson]

Date: Mon, 12 Dec 2016 20:50:04 +0200
From: Vic Rosenthal 4X6GP <k2vco.vic at gmail.com>
To: Amps reflector <amps at contesting.com>
Subject: [Amps] TL922 efficiency


I suspect my measurements are incorrect, and possibly someone with 
another TL922 can give me a sanity check.
On 40 meters, I am measuring the following into a dummy load:

Output: 1200 watts (several reliable wattmeters agree).
Drive: 65 watts.
Grid current: 200 ma.
Plate current: 580 ma.
Plate voltage 2600 V under load (3 kV no load).
Zero signal plate current: 140 ma.

This represents an input power of 1508 watts. If I assume that 60 watts 
of the output is fed through from the input, then 1140/1508 = 0.76, or 
76% efficiency. I find this hard to believe. I am wondering whether the 
plate current or voltage measurement is wrong.

My amp has the grids directly grounded, if that means anything.

What do others see from TL922's?

-- 
73,
Vic, 4X6GP
Rehovot, Israel
Formerly K2VCO

##  My guess is the  plate current meter is reading way too low.    I never subtract the
drive power or a portion of the drive power, from the PO. 
##  I get on my L4Bs...  
800 ma plate current
300 ma grid current.
2500 vdc under load. 
110 watts of drive.
1290 to 1320 watts output
This is on 40M. 
64-68% eff is typ on 40m  with most GG amps. 

Jim  VE7RF