Re: [Drakelist] T-4XB neutralization?

[Robert Ladden]

I use GE's in my T-4XC and they neutralized easily without modification, with the variable cap near half meshed (pretty good). Oddly, I had RCA's that I could not neutralize. But by the 1970s it was hard to tell who really made what tube. Look for a series of dots by the tube number stamp. Tubes with the dots probably were really made by GE, sometimes for other brands (I read this somewhere and I have a batch of GE's and off brands with dots).

Sometimes it is hard to find the sweet spot on 10m. Try starting on 15m or 20m and then fine tune the neutralization on 10m. I read this tip on one of the Drake user web sites.

73,
Bob WW3QB

At 08:44 PM 8/28/2008, you wrote:

A Drake technical bulletin issued when Drake could no longer get Sylvania 6JB6s and they had to begin substituting GE brand ones, says the following:
 
The T-4X series transmitter uses a 6 pf @ 2KV padder capacitor (C-48) across the neutralization capacitor (C-49). You must experiment with a small value capacitor across the existing padder C-48 to achieve proper neutralization.
 
I have several sets of matched GE and RCA brand 6JB6s that I am having trouble neutralizing. Anyone have any idea what "small value capacitor" means in this context?
 
TNX ES 73 DE MIKE WA3WOM K


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