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Robyn SB-520 low AM modulation

Lkaskel

Lkaskel

Well-Known Member
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Aug 4, 2017
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Hey Everyone,
So I have this SB-520 that I talk on once in a while on SSB and it sounds terrific. I have not talked on AM in a few years but someone was local and asked me to jump on. The modulation was very low. Around 30%. I tried a few mics and nothing hepled. I put it on the bench and VR7 (mic gain) does not affect it at all. The radio does not have any mods and if the limiter was clipped I think it would drive it over 100%, right? Any thoughts?

Thanks as always!!
 

Just a wild guess, but could it be a bad 48 year-old electrolytic cap? Or maybe even two of them? Or they might all still be good.

VR7 is the AM modulation limiter. If the mike gain is too low for it to kick in, you'll see no change from it. VR6 is the mike gain. Try that.

73
 

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  • @ BJ radionut:
    +1
  • @ heartbreaker3473:
    Hello gentlemen and Ladies. I have the dreaded RCI-2990 receive issue where my radio gets distorted when people get close to my location. I found the C90 Capacitor, but I can not for the life of me find the C89 capacitor. Can or does anyone have a picture of the exact location of C89 ? Thank you in advance, Wes
  • @ AudioShockwav:
    Wes, it's better if you start a thread on the main forum, more people are going to see your question.
  • @ heartbreaker3473:
    Okay, sorry, will put in a forum
  • @ heartbreaker3473:
    I put it in the general disscution help area and started a new thread. Thank you for letting me know.


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