[Amps] GS-35B tube issue

[Paul Baldock]

At 11:59 AM 12/26/2016, Steve Wright wrote:


>You are a little light on details with regard to hours, drive, 
>output, and bands of operation - probably for a good reason.  ;)
>
>Steve

Probably on the existing tube less than 100 hours, drive 10W of 100% 
modulated AM (yes you remember AM), output 300W of carrier 1200W PEP 
with modulation, Plate current carrier only 300mA until modulated, 
mostly 40M and 15M.

- Paul



On 27/12/16 06:00, Paul Baldock <paul at paulbaldock.com> wrote:
>I have a home brew GS-35B amp built around 5 years ago. I run about
>4KV on the plate. I purchased 2 NOS tubes at the same time. Initially
>when I built the amp I needed around 40V of bas voltage for idle
>current of about 120mA. Over the next few years, and with little use
>the idle current gradually rose and I gradually increased the bias
>voltage to compensate and about a year ago at maximum available bias
>voltage of 54V the idle current was about 200mA. At this point I
>replace the first tube with the second tube, set the bias voltage at
>40V and had an idle current of 110mA. Now a year later the idle
>current has crept up to 200mA (at the same 40V bias).