[Amps] grid fuses

[Tom W8JI]

> Not really,
>
> its quit common that tubes like YL1050, TH347 etc. which 
> are very high gain
> metal ceramic tetrodes for linear mode of small 
> tv-transmitters and linear
> service arc internally from time to time.
> It does not matter whether they are new out of the box or 
> being in service
> for a long time.
> Those tubes are extremely expensive and nobody throws them 
> away.
> Everybody uses the circuitry in the power supplies which 
> the manufactory
> suggests and never a grid fuse or grid resistor but direct 
> ground
> connection.
> The YL1056 in my 2m amp is running now perfectly for 
> almost 20 years with
> regular arcs even in standby, it does not matter at all, 
> the P/S quickly
> resets and during a contest I do not loose any qso by 
> that.
>
> 73
> Peter

Thanks Peter,

I was sure anyone with experience in manufacturing new PA's 
with power grid tubes would know this, but maybe some do 
not. I guess it is good to repeat it.

If I tossed back 3CX3000A7's that arced when brand new, 
about 50% would go back. Those very same tubes, once 
"burped" a few times, give many many years of service. This 
is really common with many tube types in many classes of 
service.

If it wasn't a problem, the factory would not put active 
getters in large power grid tubes!

73 Tom