[ICOM] IC756PRO3 no tranmit and receive audio

[Stephen Budensiek]

George,
   This got dropped in my spam filter.   Just caught it.
   One thing that will kill all TX and RX audio is the DSP module getting
knocked out.   The DSP board both decodes all modes on RX, and decodes all
modes on TX.   There's a few IC's as I mentioned above also that can do
it.

73's de Stephen, K0SD


On Wed, Jul 31, 2013 at 10:22 AM, George Szymanski <du1gm at dxhams.net> wrote:

>
> 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
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