SB-101 transmit audio problems...

[wa1vwl]

Testing by substutition is an excellent idea. It's done all the time in
the commercial field. It's also common among smaller companies who can't
always afford the best test equipment. Certainly, at one time, the radio
must have worked properly or at least designed to work that way. As for
the engineers being smart and spending years in the design process,
there is some truth in that. However, the engineering teams almost get
trampled by marketing types when it comes to bringing out a product.
That is to say, the engineers do a pretty good job with the design. Then
what happens is the sales/marketing people try to reduce the design to
its bare essentials to save cost and lower the selling price. There
isn't a single piece of equipment out there that couldn't use a little
help in the design department.

73/Gerry/W1ID

Ed Richards wrote:
>
> 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
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> >
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