RF problem with Headphone Amp on SD 442

Hi Bob,

I tried turning and pushing the volume knob quite a bit but no
change. I also tried slight sideways pressure but no change. Since
the master pot is also reactive, although not to the same degree, I
wonder if it could be some other common ground problem between the two
pots.

Andy
 >> Stay informed about: RF problem with Headphone Amp on SD 442 

"Andy Turrett" <aturrett.DeleteThis@aol.com> wrote in message
news:4da85a78-0b03-494e-a95c-a059965f96e9@l64g2000hse.googlegroups.com...
Here’s a puzzler.

I noticed while using my SD 442 with my Zaxcom TX as a camera link
that every time I touched the headphone pot with my finger I would
here an RF sssssshhing sound in my headsets. When I removed my finger
it would go away. If I touched the headphone pot with one hand and
with the other hand touched the Zaxcom TX antenna or the audio cable
feed to the Zaxcom TX the sound would go away. This sound is not
getting into the audio and is not being recorded and I only hear it in
my headsets. I tried a bunch of different scenarios but they all
result in the same problem. I tried removing all my Lectro RXs from
the bag. I turned down all 4 audio pots. I ran both the mixer and
Zaxcom TX on external and internal power. I tried different
headsets. I disconnected all output cables. I am guessing that some
RF is getting into the headphone amp. It’s strange because it just
started doing this and I never had this problem before. Does anyone
have any ideas?

Thanks,
Andy
-------------------------------------------------------------------------------------

There may be a wiper on the shaft to ground it out, that has accumlated some
resistance. Try push-detenting the knob multiple times to clean it up.

Bob Morein
(310) 237-6511
 >> Stay informed about: RF problem with Headphone Amp on SD 442 

"Andy Turrett" <aturrett.TakeThisOut@aol.com> wrote in message
news:8f1b9770-2bc8-4cf8-9820-095f66cfcd23@a23g2000hsc.googlegroups.com...
>I tried pushing the volume pot a number of time but no change. But
> thanks for the suggestion Bob.
>
> I forgot to mention that this problem does not happen with my SD 302.
> In playing with my 442 some more I noticed that if I turn the
> headphone pot to wide open that the noise goes away when I touch it.
> I also noticed that when I touch the master volume pot that it also
> makes this RF ssshhing sound but not as loud.
>
> Andy
>
>
>> There may be a wiper on the shaft to ground it out, that has accumlated
>> some
>> resistance. Try push-detenting the knob multiple times to clean it up.
>>
>> Bob Morein
>> (310) 237-6511
>
My guess is that the wiper has gone bad. Bad crimp? Heavy corrosion? I
hesitate to suggest a pot cleaner, because they wash the lubricant out of
the pot, which is still functioning normally.

Give it some concerted exercise before giving up. Also, try mild sideways
pressure on the knob as a diagnostic.

Bob Morein
(310) 237-6511
 >> Stay informed about: RF problem with Headphone Amp on SD 442 

"Andy Turrett" <aturrett.TakeThisOut@aol.com> wrote in message
news:0d88ea32-9353-4771-92e8-1be9776d4fbe@a70g2000hsh.googlegroups.com...
> Hi Bob,
>
> I tried turning and pushing the volume knob quite a bit but no
> change. I also tried slight sideways pressure but no change. Since
> the master pot is also reactive, although not to the same degree, I
> wonder if it could be some other common ground problem between the two
> pots.
>
> Andy

Sounds like a good guess to me.

Bob Morein
(310) 237-6511
 >> Stay informed about: RF problem with Headphone Amp on SD 442