[TenTec] [Fwd: 555 help] - forwarded on behalf of KE6GFF/T6EE

[Dr. Gerald N. Johnson]

On Mon, 2008-06-30 at 20:13 -0500, Stuart Rohre wrote:
> It might be RF getting back into the audio circuits, one thing to try is 
> open up the radio and loosens and retighten all screws that ground shields 
> and braids to board ground planes or case.
> 
> Also, 555 is an older radio now, and electrolytic capacitors might be 
> subject to needing replacement.
> Check for large values in audio stages.
> 
> Does the radio do this with a dummy load in place of antenna?  In that case 
> it might be a capacitor going bad.
> 
> If it is OK on dummy load but not on dipole, try RF ground fixes, or move 
> antenna further away from the radio.  Likely it RF if only seen on the 
> dipole.
> 
> Stuart Rohre
> K5KVH 
> 

One other test for spurious outputs. Use the tuner on the dummy load.
The tuner bandwidth will be similar to the tuner bandwidth on a nearly
resonant antenna. If the tuner can't be tuned to a perfect match with
the Scout, then the Scout is putting out RF at two different
frequencies. That could come from bad circuit board grounds or a tuned
circuit problem on the band plug in, possibly only mixer balance or
alignment.

73, Jerry, K0CQ