[R-390] R-390A Audio hiss

[bw]

> Gassy tube, noisy resistor, leaky capacitor?  Haven't noticed hiss from the
> receivers here.
> 
> 73 de Bill, AB6MT
> billsmith@ispwest.com

> Having just become the proud owner of an R-390A. I
> have a question to pose.  Having used an R-392 for
> a while, 600 ohm audio/xfmr to 8 ohm Heath SB-600
> spkr with excellent audio(using minimal RF gain). I
> find that using the same spkr/xfmr from either the
> "local" or "line" outputs on the R-390, I have a very
> objectionable hiss from the spkr constantly.  Can
> anyone tell me what I'm doing wrong?? Joe, K0AHD

Joe,

Maybe you need a bit more advice on this one. Well, it could be anything.
Maybe trying the simple things first will find the problem. Do you have
spare tubes? You need those anyway. Swapping out the audio deck ones first
is easy and may cure the hiss problem. If not, resolve yourself in swapping
out all of them.

While you are at the swapping tubes job, take the time to test the originals
and your spares on a tube tester. It may not give totally accurate readings,
but make notes. It may help later down the road. Since you have the tubes
out of the radio, clean the pins good. A soft, nonabrasive rubber eraser cut
to size works wonders. Put a tiny drop of DeOxit on each pin. You may find
the results sounding like a new receiver...like I did on mine.

You can try the Gain Adjust next to the Carrier Meter Adjust with the radio
receiving. I've done this on 2 radios and found that there is only a little
bit of room to adjust down out of the noise without decreasing apparent
sensitivity. My radios never had that much high end noise to qualify as
audio hiss, but give it a try. Maybe yours is cranked way up and could use a
lot of backing off. It only takes 1 or 2 minutes.

Get back to us about the hiss. It could be something else that requires cap
or resistor replacement(s).



Barry non-nonA aka non-Hauser