[Amps] GU74B's

Bill, W6WRT dezrat1242 at yahoo.com
Tue Aug 25 08:30:58 PDT 2009


On Mon, 24 Aug 2009 21:48:37 -0700, "Dave Hachadorian" <K6LL at ARRL.net> wrote:

>I have a commercial amp that uses a pair of GU74B's 
>(4cx800a's).  Due to a recent cable failure in the filament 
>circuit, there was no filament voltage, but plate voltage, 
>screen voltage and RF drive were applied.  After I get the 
>filament cable problem fixed, can I expect the tubes to have 
>Dave Hachadorian, K6LL
>Yuma, AZ

Yes, the tubes will be fine. Tubes can be damaged by operating them with the
filament voltage on the low side, but with no filament V at all, no harm will be

73, Bill W6WRT

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