[Heathkit] SB 220 vertsus Amp Supply LK 500 ZA power readings

[Ron Youvan]

   On 11/18/2015 01:47 PM, John K5PGW King via wrote:

> I have several amplifiers that use  two 3-500ZG tubes as amplifiers. Based on my 57 years of hamming, I have noticed most are very similar and mostly knock Offs of the SB220 series.B. C. tubes (before China tubes) my SB 220 used Eimac tubes which would last 0 years in Amateur service, if not abused. My SB 220 would do 1100 to 1200 watts out with 75 or so watts of drive and 700 to 750 watts with one (1) Eimac 3-500Z (non ZG). Less power out per tube was due to power supply constraints, thus three fourths as much power  out with one tube as with two tubes.

   The SB 220 was designed for 1,000 Watts INPUT plate power the then
legal limit and 600 to 700 was probably the limit depending on how much
distortion and splatter you generated.  The limiting factor was the
plate supply which matched the law at the time.  Anyone that got more
from an original SB 220 was obviously using an uncalibrated power meter.
When we buy a good power meter now they are usually much more carefully
calibrated.
   Most other amplifiers were supplied with a more powerful power supply.
   My understanding is that no SB 220 can output 350 Watts unmodulatd
carrier in am service as a linear amplifier driven from a rice box, but
other amplifiers with a pair of 3-500's can.

> NOW  A. C. (after China tubes) I only get 750 to 800 watts from two china made tubes in my SB 220 with APPROX 3,000 Vdc. on the plates of the China tubes measured with a Fluke meter and Fluke hV probe. That is with 75 watts of carrier from my Ten Tec Omni VI transceiver.
> However using same China tubes (different pair but  same age and use),  in my Amp Supply LK 500 ZA, I get at least 100 to 1200 watts out wit same drive from same transceiver.
> The SB 220 acts like it has one tube and the Amp Supply acts like two tubes as far asp power output is concerned.
> I bought eight  3-500ZG tubes at the same time from the same seller and of the same brand. One of the eight shorted after only slight use. I am puzzled about the disparity between the two amps using tubes of same age and origin. Anyone had this experience with the SB 220 and China tubes. I MISS EIMAC SO MUCH !!!!!! Your input will be appreciated. 73, John, K5PGW
-- 
   Ron  KA4INM - Youvan's corollary:
                 Every action results in unwanted side effects.