[Amps] AMP TUBES

[Roger (K8RI)]

David H Craig wrote:
>     Just curious- my understanding was the RUs are still manufacturing 
> GS35bs- am I wrong on this account?  I have a "stock" onhand but am worried 
> they too will become scare if this is the case.
>   
The tubes are apparently still available in quantity, but whether they 
are still being manufactured or not?
>     FWIW I haven't the multi-amp bulding experience of others, but I can say 
> this- unlike the 3CPX800 / 8877 etc, the GS35b can take all the abuse you 
>   
I like the 3CX and 4CX 800's, as they are a known quantity when it comes 
to parting with an amp, but I do like the GS35B
> can throw at it.  I don't even bother measuring grid current.  Doesn't give 
> quite the gain of an 8877, but more than sufficient for legal limit.  I can 
> also lose 4-6 of them for the price of one screw-up with an 8877 or 3CX800, 
> though I haven't had that problem either.  My current GS35b project(s) are 
> on on 6m, and the primary homebrew GS35b amp has been QRV for 2 years now...
I also like the idea of being able to use the same tube for HF and VHF.  
Amps are pretty well out for UHF as her in this part of Michigan we are 
limited to 50 watts out.

As for lifetime, I drive the snot out of a pair of 8874's (3CX-400) and 
they are still going strong after 5 years. OTOH I'm careful on tuneups, 
but as I've said before, if there is a mistake that can be made I'm 
probably the one who'll do it. Particularly if it costs money. <:-))
>  
> over that time I watched local friends replace 8877s & multiple 3CX800s 
> while the Russian tube keeps chugging right along with 3875V on the plate 
> and a lower-than-spec blower CFM flow.  My SB220 6m conversion did well for 
> years on Eimac moly 3-500Zs, but the Chinese version didn't last 2 years 
> before they softened (probably heat, but who knows?).
>   
I like the idea of the 4CX1500A with the thorated tungsten filament 
(Instant on), but that sucker uses over 200 watts on the filament (5V at 
38.5A)while the B version has the oxide coated cathode and runs only 6 V 
@ 10A or 60 watts.

I probably never will build anything, but I like to keep dreaming. <:-))

OTOH I like the way the heat sink attaches to the GS35B so it can easily 
be converted to liquid cooling.
I'd really like to do that with the computers in here.  It'd sure be a 
lot quieter although the new low velocity coolers are much quieter than 
the old style.

73

Roger (K8RI)