Noise

[Jim Bo]

Glen,

Had a similar problem with an SB-313.  As I advanced the audio, it would break into and out
of oscillation.  As Ed states, make sure the voltages from the power supply are "clean" and
don't oscillate when you have the volume set such that it happens.  You will need a scope
for this.

In my  case, I had some old electrolytics that were in the audio amp circuit that were
leaking and out of spec.  Some of the ESR's were 20's of ohms and the values were way out of
spec.

I replaced all the electrolytic caps (in the audio amp section) with new ones and also
changed two  of the feedback caps (typically in the thousands of pico farads range) and all
worked fine.  DO NOT think by putting higher values of caps in the circuit, that you will
get better performance.  Stick with the same values (I did not at first and went with bigger
lytic's) as some of the values have an effect on the A.C. response (hence how prone it is to
break into oscillation)

Mike works very good now.

Good luck.

Jim
****

Ed Kotkiewicz wrote:

> Glen Haggard wrote:
>
> > I am getting a strange buzzing sound from my SB-600 speaker when I turn the
> > volume more than half way up on the SB-102. Otherwise, everything works
> > great. If I continue to turn the volume up it eventually sounds like some
> > type of oscillation.
>
> EK> I think you probably have a filter cap that is leaking.  Look at the power supply
> first.
>
> Ed
>
> >
> >
> > Glen Haggard KK7IH
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