SB-110A - Low xmt audio problem

[Dan Osborne]

Hello fellow Heathens....

Due to the untimely death of my IC551 during a lightning storm, I am returning
my 1970 SB-110A to the air this week. I am the original builder of this rig
and
have fond memories of the many contacts made with it over the years.

This rig has always been plagued with 'low' xmt drive on SSB - about 50w out
is all I have ever seen. However, when switching to tune or cw mode I always
get 100+ watts out with no problem. All the tubes are tested very good and the
mic/cw control responds correctly with a nice smooth adjustment of power out
in all modes.

The only 'abnormality' I noticed during alignment is the peak xmt output of
the 1st IF amp occurs about a quarter turn away from peak rcvd signal. If this
IF stage is tuned for max rcv, the SSB drive drops and 10 watts is all the
output available. Peaking this stage for max xmt yields 50 watts out but
reduced IF gain in rcv mode.

I seem to remember someone mentioning there was a design problem with
the balanced mod in this rig and some components had to be changed for
a better interstage match.

All suggestions and comments most appreciated - hope to see you on 6m !

tnx es 73,
Dan Osborne MCNE/MCSE
WB5AFY
dosborne at tcs003.chipshot.net

Sponsored by the City of Tempe 

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