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

[Chris Kepus]

Hey John,  there’s been a lot of discussion on the forums I monitor about the importance of getting a low swr match between the transmitter and the amp by careful tuning and adjustment of the amp’s input network for each band.  Some of the reasons for this attention to adjustment are mentioned by you as symptoms suggesting a not so good match between the Omni VI and the 220 compared to the match between the Omni VI and the LK500.    Or, the possibility that there are significant differences between the pairs of tubes you’re using despite their being the same brand, same age, and same use, and same drive.

Is the situation you described true on every band?

Have you measured/monitored the swr between the Omni and the two amps on each band?

Have you swapped the Chinese tubes (pairs) between the 220 and LK500 to see if you get the same results prior to the swap?

I’m sure the amp veterans will chime in.  Good luck.

73,

Chris

W7JPG

 

From: Heath [mailto:heath-bounces at puck.nether.net] On Behalf Of John King via Heath
Sent: Wednesday, November 18, 2015 10:47 AM
To: Heathkit1; Heathkit2; yahoogroups
Subject: [Heath] SB 220 vertsus Amp Supply LK 500 ZA power readings

 

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.

 

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