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Sorry guys, I guess I still don’t totally understand it. I redrew the schematic for the Uniden Washington AMC to see it better, but I am stuck on a couple things.

What I figure so far is that R99 and TR32 forms a voltage divider (when TR32 conducts) that attenuates the mic audio going into the mic amp. For TR32 to start conducting, TR31 must start turning on. For TR31 to start turning on, its base needs to be pulled below 7.3v. For that to happen, the emitter voltage at TR33 must drop below 0.3v (because its base is fixed at 1v). R124 and R125 form another voltage divider, this time sampling from the AF power regulator/driver collector supply and passing along 31% of it to the emitter of TR33. That being the case, I assume, and this is where I start to get confused, the power regulator needs to be providing 0.94v or less to R124 for the AMC to start activating. Going across two voltage drops (the darligton pair power regulator), that’s about 2.32v at the base of the regulator before the AMC starts waking up without the path of D42 and R122 influencing anything.

The part that I have trouble understanding is that if the AMC is already turning on before the audio amp swings low enough to turn off the power regulator (before D42 can conduct), what does the path of D42 do? I am going to guess that when the audio from the mic amp swings lower than 2.32v, that decoupling capacitor charges through the speaker and moves the DC bias point up just enough that the negative peaks don’t pinch off??? And so far I have only seen how negative peaks are controlled here, not positive ones. I am clearly missing something and I feel like there is also some RC time constant stuff going on that I don't understand. What am I missing?

Thanks!!!

<blockquote data-quote="brandon7861" data-source="post: 825650" data-attributes="member: 53724">Sorry guys, I guess I still don’t totally understand it. I redrew the schematic for the Uniden Washington AMC to see it better, but I am stuck on a couple things.What I figure so far is that R99 and TR32 forms a voltage divider (when TR32 conducts) that attenuates the mic audio going into the mic amp. For TR32 to start conducting, TR31 must start turning on. For TR31 to start turning on, its base needs to be pulled below 7.3v. For that to happen, the emitter voltage at TR33 must drop below 0.3v (because its base is fixed at 1v). R124 and R125 form another voltage divider, this time sampling from the AF power regulator/driver collector supply and passing along 31% of it to the emitter of TR33. That being the case, I assume, and this is where I start to get confused, the power regulator needs to be providing 0.94v or less to R124 for the AMC to start activating. Going across two voltage drops (the darligton pair power regulator), that’s about 2.32v at the base of the regulator before the AMC starts waking up without the path of D42 and R122 influencing anything.The part that I have trouble understanding is that if the AMC is already turning on before the audio amp swings low enough to turn off the power regulator (before D42 can conduct), what does the path of D42 do? I am going to guess that when the audio from the mic amp swings lower than 2.32v, that decoupling capacitor charges through the speaker and moves the DC bias point up just enough that the negative peaks don’t pinch off??? And so far I have only seen how negative peaks are controlled here, not positive ones. I am clearly missing something and I feel like there is also some RC time constant stuff going on that I don&#039;t understand. What am I missing?Thanks!!!</blockquote>

[QUOTE="brandon7861, post: 825650, member: 53724"] Sorry guys, I guess I still don’t totally understand it. I redrew the schematic for the Uniden Washington AMC to see it better, but I am stuck on a couple things. What I figure so far is that R99 and TR32 forms a voltage divider (when TR32 conducts) that attenuates the mic audio going into the mic amp. For TR32 to start conducting, TR31 must start turning on. For TR31 to start turning on, its base needs to be pulled below 7.3v. For that to happen, the emitter voltage at TR33 must drop below 0.3v (because its base is fixed at 1v). R124 and R125 form another voltage divider, this time sampling from the AF power regulator/driver collector supply and passing along 31% of it to the emitter of TR33. That being the case, I assume, and this is where I start to get confused, the power regulator needs to be providing 0.94v or less to R124 for the AMC to start activating. Going across two voltage drops (the darligton pair power regulator), that’s about 2.32v at the base of the regulator before the AMC starts waking up without the path of D42 and R122 influencing anything. The part that I have trouble understanding is that if the AMC is already turning on before the audio amp swings low enough to turn off the power regulator (before D42 can conduct), what does the path of D42 do? I am going to guess that when the audio from the mic amp swings lower than 2.32v, that decoupling capacitor charges through the speaker and moves the DC bias point up just enough that the negative peaks don’t pinch off??? And so far I have only seen how negative peaks are controlled here, not positive ones. I am clearly missing something and I feel like there is also some RC time constant stuff going on that I don't understand. What am I missing? Thanks!!! [/QUOTE]

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