SB-101 transmit audio problems...

[Ed Richards]

Sandy;
I am very much against trying to out-engineer the engineers. There is a
very good reason for the value of every component in a radio. When you
start changing values you change the performance specifications of the
radio. Besides allowing more audio through, you will upset the frequency
response, VOX performance, possibly overdrive the modulator, and other
things neither of us has thought about. The designers spent months, maybe
years fine tuning the circuit for best performance. Are you smarter than
them? I have a SB-101 with plenty of audio. Something is wrong with
yours. It is better to find the problem than cover it up with band aids.
Take a working radio and a 'scope and compare levels as you go through
the circuit. Start at the mic jack with a 1000 cps tone that produces
full modulation in a good radio. Good luck.
Ed Richards


On Mon, 19 Jul 1999 19:39:08 -0400 Sandy Gerli <angerli at ESSLINK.COM>
writes:
>Hi, folks,
>
>Well, this one has me foxed. My SB-101 puts out tons of rf in Tune,
>but
>is weak as a stone on SSB. All voltages check within tolerances to
>the
>manual. V1 has been changed to a 6CQ8 for more gain per recommedation
>of
>Jim Ray's notes on 'JJL (?)'s website archives. Still weak.
>
>Which brings me to the schematic. Interstage coupling cap C9 from the
>plate of V1A to the MIC/CW LEVEL control is a .01uF. Could that be
>pumped up to a .05 or perhaps a .1? And, C11, from the wiper of the
>MIC
>control to the grid of the cathode follower V1B is a puny .001uF;
>could
>that be pushed up to .005? Has anyone tried these to increase audio
>gain?
>
>This sure puzzles me. Using a mic with known good gain (Heath/E-V
>stock
>mic for the SB-series, so it ain't the mic.
>
>As a postscript, what about the series input resistor R931 from the
>mic
>jack to the grid of V1A; that's a 22K. Has anyone tried to change
>that
>value to let more snort through?
>
>Thanks for the bandwidth. 73,
>--
>Sandy Gerli, AC1Y
>500 Country Club Road
>Avon, CT  06001-2406
>(860) 675-5566
>E-Mail: angerli at esslink.com
>
>Life Member: ARRL, QCWA
>Collins Collectors Association
>Hallicrafters Collectors Association
>
>Boatanchors are Ham Radio's living heritage!
>Restore something! Smell that hot solder!
>Sure beats booze. And, you can get up afterwards!!
>Keep your finals dipped...
>
>Sponsored by the City of Tempe
>
>Listserver Submissions:  heath at listserv.tempe.gov
>Listserver Subscription: listserv at listserv.tempe.gov - "subscribe
>heath 'name' 'call'"
>Listserver Unsubscribe: listserv at listserv.tempe.gov - -"signoff
>heath"

Sponsored by the City of Tempe 

Listserver Submissions:  heath at listserv.tempe.gov
Listserver Subscription: listserv at listserv.tempe.gov - "subscribe heath 'name' 'call'"
Listserver Unsubscribe: listserv at listserv.tempe.gov - -"signoff heath"