Hi Bruce and other tone on the band friends,?
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I have made no progress other than to speculate that replacing the 74CBT3251 'front end' chip might be an option.? Since the tones disappeared when IC402 was bad, but the radio sounded fine other than totally deaf, I speculate that the only other device in the path is IC408.? By 'sounded fine' I mean there was no 1000 Hz tone, and the CW filter settings produced the expected audio, etc. etc. just no signals.? I have an order for IC408 and am adding other things to that order for another dive into the radio in the next two weeks.
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As an aside, and probably worth its own thread, I have found that IC401 is essentially not available to the experimenter at this time, except from Amazon with long lead times.? Looking for the CS4334KSZ chip, I find it is discontinued as obsolete, or available from a third party thru Digikey in minimum quantities of 175+.? Other known vendors that I checked seem to have similar stories.? ?The chip has suddenly become a needle in a haystack.? I would love to find just one to satisfy other questions I have concerning the tones presence.? If you have one to supply, please contact me at rhattaway at rocketmail dot com.
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I will post more when I have time and have more new info.
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73
Dick
W4PID
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Richard Hattaway