[Amps] SB-220 6 Meter Conversion

[RICHARD SOLOMON]

I ran some tests on my conversion of an SB-220 to 6 Meters and got

the following. These were key down tests, Bird 43 on output and

Motorola on Input, into a Bird 2.5 KW Dummy LOad.

 

CW Position (Power Switch)

80 Watts of Drive gave 700 Watts output. Efficiency was 54%

100 Watts of Drive gave 750 Watts output, efficiency still ~ 54%

 

SSB Position

100 Watts of Drive gave 1,050 Watts output, efficiency 55%

 

Efficiency calculation used the Heath Ip and Ep Meters (so +/- 10%) ?

 

The first test was at low power (35 Watts drive) and one of the

three suppressor resistors on one tube cooked. At high power

everything was stable. 

I need to look into maybe changing the suppressors, but I'll wait

until I get more time on it and see what happens.

 

These tests were done with the original tubes that came with

the amp. Both are Eimacs but have different plate structures.

One is the standard vertical fin Eimac style but the other is the

"stacked disc" plate that reminds me of Amperex. But both are

clearly marked EIMAC.

 

I will be putting in a new set of tubes before I put it on line. That

may increase my efficiency some.

 

All in all, a fun project.

 

73, Dick, W1KSZ