[ICOM] IC756PRO3 no tranmit and receive audio

[George Szymanski]

Hi Stephen,

I did have the CI-V connected when things went bad, but nothing
connected to either ACC socket.
I haven't been able to test CI-V since then so I don't know if that is
also faulty. I will try it in a week or so as I'm slowly rebuilding
the HB  interface which was getting a bit messy looking.

I did a few tests yesterday....
RX display and all controls are ok. The rig shows signals on the
screen when an antenna is connected.
On receive there is no audio from the speaker or phone socket. I don't
have a signal generator to test the ACC1 audio in but I did get some
hum transmitted on SSB from the finger hum generator! 
I don't have an audio amp to test the af out from ACC1.
The rig does transmit carrier on AM and FM but I can't hear any
modulation on an adjacent receiver. On SSB, if I use high gain on the
mic (SM-8) and turn up the mic gain on the rig I can then hear my
voice. I can almost obtain full output of the rig but only with all
the mic gains at max. There is then a lot of background noise as well.
A recorded CQ on SSB is also audible with the same noise.

From what you said, the audio mute is a possible culprit. I wonder
what the common link is between tx and rx as far as the audio is
concerned? 
I rather suspect that the mic input, which was connected to the
computer, was spiked by the nearby lightning strike and the fault
spread from there.

Lots of clues there I think!

Being retired I can't afford to spend much on repairs so I will have
to do it myself and would appreciate any help and pointers.

Thanks and 73 de George, DU1GM


>George,
>   I had a similar problem about a year ago with a IC-756Pro.   Do you have
>the CI-V connected to the computer?  Did you loose that also?  I had Q652
>fried, Q3772 was burnt, some chokes were burnt open around the back acc
>plug where I interfaced to the RTTY DSP audio in and out in the computer,
>IC311 and IC331 in the audio mute circuit was blown.   It had come in the
>demod line on the acc socket, and gotten several IC's.  Got it repaired,
>but it was a little crazy for abit.
>
>73's de Stephen, K0SD