Normal power output, but as you would expect I need a little more
drive as the bias voltage is increased.
Drive power is 10-12W of carrier with around 120% upward modulation,
so that's about 50W PEP drive, and 1300W PEP output.
I will check the filament voltage, but I think I will find it in spec.
- Paul
At 09:25 AM 3/10/2018, you wrote:
Paul, sounds to me like your filament voltage may be too low, or else
you are cooking the grid by driving the tube too hard (grids are
usually plated with gold or other metal that will evaporate if the
grid is overheated). Either will greatly shorten the life of tubes
with indirectly heated cathodes. Are you getting normal power output?
Sent from my iPhone
> On Mar 8, 2018, at 10:09 AM, Paul Baldock <paul@paulbaldock.com> wrote:
>
> I built a GS35B amp a few years back to be used with my home brew
AM rigs. Initially I set the idle current at around 110mA/4KV
requiring about -35V bias. Over a few years of very little use the
idle current drifted up so I increased the bias voltage to get it
back down. Eventually I was up to -55V with the idle current at
around 180mA, and so I installed another tube (purchased at the
same time as the first). Same deal as before, started at -35V, now at -55V.
>
> Is this 2 bad tubes, or could I be doing something wrong? I'm
getting ready to install a third tube purchased from a different source.
>
> - Paul KW7Y
>
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