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Author Topic: TS440s Severly decreased mic audio output  (Read 59 times)

N4EF

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TS440s Severly decreased mic audio output
« on: October 25, 2020, 05:22:57 AM »

I am the original owner of a TS440s and it's stock hand microphone.

There is virtually no microphone audio output on transmit regardless of the front panel MIC knob control setting as tested on 40 m LSB.

Both sides of the microphone element shows continuity to the mic plug.

NOTE: if I set the front panel MIC setting to Maximum (10 on the front panel scale) and literally scream into the mic, the S-meter needle deflects about a millimeter or two. The radio's audio circuit is apparently engaged, but shows near zero audio output.

What would be the likely culprit for me to investigate?

Thank you.

Dave



« Last Edit: October 25, 2020, 05:27:58 AM by N4EF »
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AC2EU

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    • McVey Electronics
Re: TS440s Severly decreased mic audio output
« Reply #1 on: October 25, 2020, 07:52:02 AM »

If you have an audio generator and a scope, you could input  a signall at the mic input to see how many millivolts it takes to get full power SSB. It should be well less than 200mv.

Considering the age of that rig, the culprit may be an electrolytic coupling capacitor in the mic preamp circuit.
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