SB303 Receiver noise.

[Michael Waldrop]

I had a very similiar problem with my SB-303. I do not have any converters
plugged into the rear of the 303 so placing the Converter switch in any
position had no affect on the noise level; it remained at S8. Removing
the antenna also had no affect on the noise level; again still S8.
I found the voltage adjustments needed attention quite often as well.

I checked other receivers, SB-300, Yaesu FT-757GX, FT-857D and a Kenwood
TS-820S, under the same environment, same power strip and antenna,
no noise. This told me the noise was being generated inside the SB-303.

A thorough cleaning did nothing to reduce the noise. The fix was to
replace the electrolytic caps on the PS/BFO and IF/AUDIO boards. The
noise went from S8 to S0 after replacing the caps. The receiver is really
quite now.

Whether this will fix your noise problem or not, I can't say. I can say
the SB-303 is over 30 years old and more than likely the electrolytic caps
are becoming quite leaky. Another thing. The voltages, once adjusted
as outlined in the manual, remained constant once the caps were replaced.
So replacing the caps fixed 2 problems, noise and voltage instability.
By the way, with the noise gone the receiver really pulls in those
weak stations; stations I couldn't hear before because of the noise.

73's
Mike
W5RKL

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