sonar BR21

[dutch2u]

the BR 21 will do about 80w with 5 driving on ch20

[721HACKSAW]

When you go to looking for those old sweep tubes and see what they cost, you will know why it was sitting in the basement.

[Night Crawler]

it uses 4 6JB6 tubes they need to be replaced.

Save some money replace the 6JB6's with 6JF6's the amp will work just as well with them.
$5.95 each NOS

[Night Crawler]

Question though is there a way to get more power out of this amp?

Change the power transformer to one that will supply more plate voltage and current to the tubes or change the rectifier from a full wave bridge to a full wave doubler.

the BR 21 will do about 80w with 5 driving

With 430 volts on the plate of the tubes a total current draw of 225ma and around 66% efficiency I don't think so maybe 45 to 50 watts with 10 watts drive.

Look at the input versus output graph in the operators manual.
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[Night Crawler]

do you think its worth changing everything in this amp to get it to do more watts

No

or just use it as a driver for a bigger amp?

That would be the thing to do like an Ameritron with three or four 811's or a 3-500z.

[bullet]

Use it to drive a bigger ampou know that. It works well for this. I had one and I am looking for another. Should have never sold the other one. Do let go of it unless you are sure you will never get in to radios.

[KKD3088]

the BR 21 will do about 80w with 5 driving

With 430 volts on the plate of the tubes a total current draw of 225ma and around 66% efficiency I don't think so maybe 45 to 50 watts with 10 watts drive.

Look at the input versus output graph in the operators manual.
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Perhaps on SSB, but on AM 33% carrier efficiency is all you're gonna get while preserving the original waveform allowing for the positive-peak headroom at 100% modulation. A rule of thumb to remember with AM linear service; carrier power output (unmodulated) cannot exceed 1/2 total plate dissipation. And that only applies if the power supply is designed to handle the much greater duty cycle of AM (compared to SSB). If not, it has to be further de-rated in output power. If a linear amplifier is driven beyond these limitations on AM, the output will be distorted, and it will splatter. Plus, tube life will be shortened significantly.