ICOM R7000 Scan Delay Circuit Description

Purpose:
The purpose of this modification is to add a "Scan Delay" to the ICOM R7000
so that it behaves like a conventional scanner. With this modification, after
stopping on an active channel, the R7000 will pause for a reply before
continuing on to the next channel. The length of the delay can be set between
1-10 seconds. 

Summary:
The Squelch signal and the Center Detect signals are combined in the Main
Circuit of the R7000 into a "STOP" signal that extends to the Logic Board.
The R7000 CPU in the Logic Board uses this signal during scans to determine 
when to move to the next station. In this modification, we add a delay to the
falling edge of the "STOP" signal. If there is no activity during this delay,
the "STOP" signal falls and the CPU scans to the next station, otherwise the 
"STOP" signal stays high and the R7000 remains in the current station. The
function of this modification is deactivated (reset) by pressing in the VSC
button on the front panel.

Note: 
Do not attempt to make this modification unless you are very familiar with
making modifications to (expensive) electronic equipment. Obviously, this will
void your ICOM warranty. Some large ham radio stores offer a similar
modification for about $50-$100. Unless you are a real hardware hacker, 
I recommend that you send your radio to them for modification. 

Description:
Please have your R7000 schematic diagram handy. The R7000 Service Manual
is very useful in locating components. The entire modification is applied
to the R7000 Logic Board. The "STOP" originates in the Main circuit and
continues to the Logic Board where it is applied to the base of Q7 via 
R36. Our circuit intercepts the signal at this point and, instead, applies
the Delayed STOP signal to the R36.

1.  Build the circuit in the attached diagram. I built mine on half of a
    Radio Shack 276-148 pc board and installed it on top of the Remote
    Control Option board with three 3/8" plastic stand-offs. I then used
    a 6 wire ribbon cable to make the connections between the Logic Board 
    and the Radio Shack pc board. I also used header type connectors to make
    it easy to disconnect the ribbon cable from the pc board. 
    The hollow circles in the diagram indicate wire connections to the
    Logic Board.
2.  Disconnect R36 from the "STOP" signal (the side not connected to Q7).
3.  Connect the circle marked "STOP" to pin 2 of IC3 by attaching it to D65.
    This is the input to our delay  circuit.
4.  Connect the circle marked "DELAY STOP" to R36 where it was disconnected
    from the R7000 Logic Board.
5.  Connect the circle marked "+5V" to R35 in the Logic Board. If you see a
    better place to pick-up +5v, go for it!
6.  Connect the circle marked "GND" to W60 in the Logic Board.
7.  Connect the circle marked "VSC" to the negative side of D8 in the Logic
    Board.

The 100 K pot generates a delay between 1-10 seconds, leaving it in the
middle, or replacing it with a 47K fixed resistor, will generate a delay of
about 5 seconds which is normal for scanners.

Please send your comments or suggestions via CompuServe to:
    Reza Pourzia 73447,671