[1000mp] FT1000MP RX/TX audio monitor

[Tod -ID]

I spent some time late last night looking through the Service Manual
circuits for the FT1000MP. 

I was able to trace the Monitor audio signal to the AF Board and once on
that Board to an IC. That same information is available if you have the
regular circuit diagrams for the FT1000MP.

For those who want to do their own inspection, start with the FT1000MP
Circuit Diagram Sheet. On the back side of the interconnection diagram and
the block diagram is the AF-Unit detailed schematic. On the left side of the
bottom of the AF-Unit diagram along the dotted lines are shown two cable
inputs from the CNTL-Unit. The right hand cable goes into jack J3019[P052].
Pin 2 of that jack is labeled MON0 and I believe is the audio line from the
monitor function.

You can trace that line up to IC U3003 which is called the I-DET-Unit. Pin 7
of that IC has the MONO line connected. Leaving that U3003 are two lines,
L-Out and R-Out ; Pins 9 and 8 respectively. If you follow those lines they
go to jack J3036 which, although shown on the right edge of the board is not
located there. It is located close to IC U3003 somewhat in from the edge of
the board. 

The interesting thing is that there seems to be NO cable that is connected
to that jack. The plug ID [P90622]is given on the schematic but there is no
indication of a place that this jack will be connected to . It may well be
that this is a simple to access point on the AF board that will provide an
audio signal that will be present when receiving or when transmitting. It
might have been put on the board so that the factory could quickly make
adjustments -- who knows? The only way to be sure is to open the radio, put
scope probes on the jack pins and look at the output when RX or TX-with
monitor switched on is selected.

Pictures of the radio show that jack J3036 seems to be easily accessible on
the top of the AF-Unit board. The AF-Unit can be seem by removing the bottom
cover of the radio [as though you planned to insert or replace a filter].
When looking at the bottom with the front of the radio closest to you, the
board with the filters will be top left and the AF-Unit top right. 

Although I am interested in finding a point such as this, I simply will not
have time to check it out for at least six weeks because of other
commitments. If indeed the desired signals are there, I would be inclined to
buffer them before sending them to the outside of the radio in order to
protect IC U3003 from "Mistakes". In fact, making a small cable that went to
a separate small board with level control circuits for the audio lines would
make it possible to not have to be concerned with the audio level selected
for the headphones. 

I will be interested in seeing who, if anyone, chooses to pursue this.

Tod, K0TO