Mike -
Before you expend too much effort in this, do you have ANY tubes that
will neutralize? The RCA and Sylvania tubes were very close to the
same and either should neutralize without difficulty or changes. I HAVE
used GE tubes without difficulty also, aside the from fact that they
seemed to fall off in output power more quickly from brand new than
either Sylvania or RCA brands. I wonder if by the time that Service
Bulletin was issued if the "GE" branded tubes may in fact not have been
manufactured by GE.
Back in the 60's, Sylvania 6JB6s (and all Zenith branded tubes) were
manufactured by Sylvania. RCA 6JB6s were manufactured by RCA. By the
mid 70's, tubes were being "cross-manufactured" and branded as tube
manufacturing plants were being shut down. So a GE branded tube may in
fact have been built by another company.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs
<www.k4oah.com>
WA3WOM 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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