[Amps] Amps Digest, Vol 123, Issue 49

[LB3HC]

There are several ways to look at how much a grid can take. The energy perspective is the best I think. Current x voltage x time = energy. Or joules = watts x seconds. An Eimac engineering bulletin says that the grid of the YC-179 can take max 4 Joules. However, I think that is quite conservative. A LTspice simulation that I did (posted on my webpage) shows that it is not easy to quench the PSU with an arcover even with a quite fast crowbar circuit. We know many amplifier with that tube in amateur service dont use crowbars and have survived many years and several arcs http://www.lb3hc.net/archives/1171 In case the Eimac bulletin is correct, that means it can only take 4J = 4W for one second. I would say 5 times that at least. Possibly more.


73
LB3HC



On 24.03.2013 17:00, amps-request at contesting.com wrote:
> A buddy just fired up his hb YC-156 today.  So far, so good.   What is the max safe grid current for this tube ?? 
> It has both electronic grid and plate current protection..which can both be set to any value.   The bias is also
> fully adjustable, so zsac can also be set to any value.   The B+ can be set to 1/2 or full voltage. 
>
> Before the drive is increased, and or B+ is doubled in value,  we need to know asap, what max grid current is.
>
> Thanks in advance. 
>
> Jim  VE7RF