>Remember there's a difference between the maximum grid current you
>would normally expect to run, and the maximum level you *could* run
>without damaging the tube.
>
>Depending on the speed of the trip circuit, it might make sense to set
>the trip level about 50% above the maximum you'd normally expect to run.
>That leaves the tube well protected, without causing too many nuisance
>trips during tune-up.
>
>The same question could also be asked about a suitable full-scale value
>for the grid current meter. I generally make it so the normal reading is
>about 2/3 of full scale, and then set the current trip at full scale.
>
>BTW, all this can be done by pulling out the tube and using an external
>power supply to force current through that part of the circuit. The idea
>is to get all the metering and protection circuits calibrated and
>working *before* the first time you light the tube,
>
>In my experience of running this tube on 50Mhz expect to see around 100mA in
>practice when the max recommended cathode emission is reached. I would set
>the grid trip higher than Ian suggested at around 225mA. The important thing
>is not to run more than an amp (average) of cathode current, the tube also
>likes 3.5kV when it really comes alive. It is a wonderful tube in my opinion
>and beats the pants off the Russian tubes despite claims of the Russian
>tubes being similar. I run both a GS35B and a 8877, give me a 8877 every
>time.
>
>I have had no problems with golden balls :-)
>
Few VHF users of 8877s aparently do. The sticky wicket is that MF/HF
amplifiers have a somewhat less than obvious tuned circuit between the
anode and the Tune-C that is resonant at several VHF and UHF frequencies.
These resonances can be found by coupling to either side of the DC
blocker C. Murphy said some things are more complicated than they look.
cheerz, Conrad
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
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