Sb-220 power output at about half..

[Glen Zook]

Sounds like one of your 3-400Z tubes has gone.  Also,
the SB-220 was designed with the 3-500Z tubes and
definitely will work better with that tube even though
the 3-400Z is capable of about 20% less power.

One thing to check is that the plate connection is
still good on both tubes.  Once-in-a-while the
connection between the wire that comes through the
envelope and the larger connector comes loose.

Glen, K9STH


--- John Godfrey <john at HUGHES.NET> wrote:

All was well and output was plenty acceptable on all
bands. Then output just went to zero after a power-on
condition. Meaning it was fine when turned off. Then
after much investigation I found that the little
bolt/nut that holds the output tuning 10/15 meter coil
to the plate tuning capacitor was loose. After
tightening and re-power up and tune. I just get half
the output as before. Both tube filaments light bright
and voltage to the pins on the filaments is 4.9 volts
ac on my meter. Cleaned the sockets and pins in case
of any resistance but like I said voltage seems to be
correct.  Both tubes EIMAC 3-400z l believe them to be
full output because I tested them in another amp.
Tested the high voltage on SSB mode and I have about
3010 volts DC. Input SWR is acceptable and I am
driving it with tubes as well instead of transistors.









Glen, K9STH

Website:  http://k9sth.com


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