Re: Need help with constant tone in audio output
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Thanks so much for responding Jerry. I answered your questions... Chuck
I assume this tone is only present during receive. Correct Do you receive amateur signals when an antenna is attached? ?Yes How does the volume of this tone compare with the volume of received signals? Very Very loud Can you describe the tone? ?Is it a steady dc note? ?What frequency? Tone is a sine wave, estimate about 800-900 Hz. Can you do things that cause the volume or frequency of this tone to change? Have disconnected all components {including display) . tone still there. Does it change in volume when you turn down the volume control? ?(If not. problem is in the LM386) Yes Does it change in frequency as you tune the radio? No Does it change in frequency when you poke your finger around C102 in the BFO? will do I suggest you work you way back through the receiver, shorting the signal to ground at each stage with a piece of wire to determine where the tone is coming from. ?Do you still have the tone when you short the top of C107 to ground? ?R37? ? Crystal side of C31? ?Crystal side of C23? ? Mixer side of C21? ?Mixer side of C13? ?Filter side of C11? ?The antenna? stay tuned for results. |
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