[Amps] 4CX250 bases

[David Kirkby]

Steve Thompson wrote:
> David Lisney wrote:
> 
>>Hi, my own little tetrode amplifier uses a conduction cooled version of the 
>>4CX250, the CCS1, my screen supply is merely a pair of BU208 television 
>>transistors, one configured as a constant current source, the other as a 
>>shunt regulator. If the screen of the valve "tries to hard" to climb towards 
>>the anode voltage a thyristor clamps it down to chassis/cathode potential.
> 
> snip
> 
>>Possibly a further consideration with these valves is to protect the bases, 
>>I don't know just how much they can stand voltage wise on the screen bypass 
>>capacitors... maybe someone else can comment?
> 
> I've just put a couple of bases on hipot. One is a Johnson 
> 124-110, the other is by AEI (quite common at UK rallies). 
> Both look very similar to the SK600 family.
> 
> On both, discernable current (<1uA) starts to flow at a bit 
> over 2kV.
> 
> Steve

As far as I am aware (the data sheets are on my web site) the CCS1 need 
a BeO base. I guess you could dispense with that if you used a small fan 
to keep the base seals cool, but if you want to run it silent, I think 
the base needs to be a special one.

I have a base and the screen decopuling capacitor is a sepparate unit - 
another of my many projects that I hope to finish one day.

-- 
David Kirkby,
G8WRB

Please check out http://www.g8wrb.org/
of if you live in Essex http://www.southminster-branch-line.org.uk/