Fw: deaf sb104a

[talen]

Sounds quite familiar.........I ought to write up what I found on mine
(I'm not done yet...waiting for a SSB filter). This may include your
problem, maybe not.


1. Poor audio, 2.No S-meter (low audio, no AGC, no AGC, no S-meter)
----------------------------------------------------------------------------------------------------
Make sure the antenna switch in the back is set to "COM" ...otherwise
   you may not have an antenna hooked up.
Make sure boards have the proper voltage levels.....10.75+/- and 4.85+/-.
Make sure the circuitry thinks you are in Rx. Check "B" board +Rx pin 7
   and *not* +Tx pin 9.
Check the "G" board for around 600-800mv p-p on HFO IN pin 6
Check the "G" board for around 700mv p-p on VFO IN pin 4
    ....basic input to get an IF OUT signal from "G" to the filter/mixer
    board "E"
Check to see "E" board has approx 100microvolts on IF OUT pin 12
Check the F board to make REAL sure the little shorting wire which
    comes installed on Q501 is completely removed (this took me a while
    to find because only some of the wire had been removed and you can't
    see until you pull Q501.
Check the "F" board audio output transistors and the LM3900 (swap it
    with the one on the "B" board to check it).
There was a "talkback fix" installed on the "F" board. R578 changed
    from 330 to 1800 ohms and R581 from 100K to 1.8M ohms. This cuts
    the overall gain to 1/4th of what it was (by the way, it was too high)
    and if you don't have the talkback problem, you might settle for
    values in between. I did.
S meter response improves quite a bit if you apply one of the SB fixes.....
    on the "F" board, replace ZD502 with a signal diode (not a SI diode)
    in the oposite direction.

Good luck !   ...and we'll see what happens and take the next step.

73s  Kees K5BCQ


----------
From: mike bryce <prosolar at SSSNET.COM>
To: HEATH at LISTSERV.TEMPE.GOV
Subject: deaf sb104a
Date: Friday, February 25, 2000 12:56 PM

everyone...

working on a sb104a. I have it working now, but it seems to be rather deaf.
Here's a tip: the s-meter wants to show -0 all the time. yes, I have the
s-meter adjustment into the stops. A really strong signal will move the
s-meter to say s-9 or so, but most of the time it just sits there.

I think it should hear better than it does/

any ideas?

--
Mike Bryce
SunLight Energy Systems
"Electricity at the speed of light"

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