I am trying to troubleshoot a no transmit problem om an icom IC-746. Part of the circuit is attached.
My understanding of its function is as follows but please correct me. I may have it wrong :-
Q1222 normally has 5 volts on its base, its collector is held high by 14 volts via R1222. This means that Q1221 has 14 volts on its base and collector via R1221, so does nothing. When the ptt button is pressed TXS is pulled to ground and so Q1222 collector is pulled to ground and so Q1221 is now switched on and thus 8V is now connected to T8V
I hope I have this correct !.. Sadly TXS is being grounded but T8V is not 8 volts so something is wrong !!
Any help much appreciated
Tony
My understanding of its function is as follows but please correct me. I may have it wrong :-
Q1222 normally has 5 volts on its base, its collector is held high by 14 volts via R1222. This means that Q1221 has 14 volts on its base and collector via R1221, so does nothing. When the ptt button is pressed TXS is pulled to ground and so Q1222 collector is pulled to ground and so Q1221 is now switched on and thus 8V is now connected to T8V
I hope I have this correct !.. Sadly TXS is being grounded but T8V is not 8 volts so something is wrong !!
Any help much appreciated
Tony
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