SB-101 transmit audio problems...

[Dave Edwards]

Sandy....

Forget about changing values to cause some effect!
It should work just fine with the original values.
Lay the mic next to the tone from a keyer or another receiver.
Now try tuning up.
Still nothing??
Any ALC reading??
There are notes on the Heath web site about poor ALC readings.
Measure with a scope from the mic input, through the audio stages,
and in to the balanced modulator. In fact, you can touch the input to the
balanced modulator through a capacitor in your hand. The 60 cycle
hum picked up should modulate it also.
You can also throw the carrier null controls all the way over and key the
mic. This will tell you if the problem is before or after that.
Divide and conquer!
...Dave
-----Original Message-----
From: Sandy Gerli <angerli at ESSLINK.COM>
To: HEATH at LISTSERV.TEMPE.GOV <HEATH at LISTSERV.TEMPE.GOV>
Date: Monday, July 19, 1999 8:04 PM
Subject: SB-101 transmit audio problems...


>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
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>E-Mail: angerli at esslink.com
>
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