[TVARC] Ameritron amplifier tubes

[EDWARD KROME]

FWIW: before he sends his checkbook off the deep end, let me suggest tht he attempt to condition the old tubes. (I've built a lot of amplifiers, mostly with ceramic tubes, and this can resurrect a surprising number). First, reseat all tubes and make sure the rest of the amp (and power supply) is all in one piece. Then, run the filaments alone for at least 24 hours. Then turn on bias and B+, no drive. Have a dummy load on the output. Don't let it oscillate. Another 24 hurs. Then, very low drive; maybe 10-20 watts out (into a dummy load), 24 hours more. Make sure each tube is doing the same thing. Then crank up the drive and see what happens. 

Ed K9EK

>     On 10/28/2020 11:42 AM Richard Antolick <ra77 at rantolick.net> wrote:
> 
> 
> 
>     A friend from high school that used to sit with me in dad’s basement while making contacts 45 years ago got his general earlier this year and has setup a station.  He bought a used Ameritron 811H amplifier and is concerned the tubes are on their last legs.  He got some advice on replacing with 572B tubes.  I have no experience with these amps but from some web searches the 572B is said to be more robust but might require some mods to the amplifier.  Any advice for my friend Ron KC3PUV on the tube change and if mods are required, also a source for the 572Bs.  DX Engineering is out of stock indefinitely and he is leery of the Russian version.  Thanks.
> 
> 
>     Rich
> 
>     W4RJA
> 
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