1. Take the three (3) back screws off.
2. Take the two (2) screws off the circuit board to free it from the case.
3. Find the red wire going to the micro-switch, ie, the ptt line.
4. Follow that red wire to the circuit board at that place on the circuit board another red wire will join the first one.
5. Un-solder both red wires from the circuit board and clean up the solder mess, otherwise hum will occur.
6. Solder the two red wires together and cover with tape or shrink tubing.
7. Put the circuit board in place and screw it down.
8. Put the "lock" slide switch back in place.
9. Put the rest of the case on.
10. Put the outside screws in.
11. You are now ready to try it out, so go ahead and re-attach it to your rig!
12. All should work:
    ptt works and releases,
    mic passes audio,
    touch tones work when ptt button held,
    touch-tone red "led" still lights up when touch-tone pad keys are depressed, even if ptt button is not held down,
    no hum noticed.

     

Open the microphone by removing the three screws on the back. You will have to lay the componants properly under and above the cuircut board. They fit in there quite nicely. I used longer leads on the 2n2222 transistor so it could be tucked nicely under the cuicut board beside the up/down buttons.

Parts needed: 1 each     2.2K ohm resistor
              1 each     10 Megaohm resistor 
              1 each     10 ufd 16 volt electrolytic capacitor  
              1 each     2n2222 NPN transistor (or equivalent)

Solder one end of the 2.2K resistor, one end of the 10 megaohm resistor and the positive terminal of the 10 ufd 16 volt electrolytic capacitor to the base of the 2n2222 transistor. Solder the other end of the 2.2K resistor to the anode side of the LED (D1). Solder the other end of the 10 megaohm resitor, the negative side of the 10 ufd capacitor and the emitter of the 2n2222 transistor to ground.

The ground terminal is pin 5 of the 8 pin connector. One side of the PPT switch is also grounded to pin 5.

Solder the collector of the 2n2222 transistor to pin 3 of the 8 pin connector. Pin 3 is also connected to the other side of the PTT switch.

To vary the time delay, change the value of the 10 megaohm resistor. The higher the valu, the longer the delay.

This mod works great. Enjoy easier mobiling.

1. turn off the radio (radio must still be connected to a power source)
2. plug in the mic
3. hold down the mic's call button while pushing the mic's pwr button

The pot fits perfect in between the two up down buttons inside the mic case. I then dialed it down and found for moderately noisy areas, 16k worked well. For very high noise areas, like concrete trucks, 11k cut the noise way back.

More info from Jim.

I am still working with the variable resistor inside, measuring it (with the mic unplugged) and have so far found that 33k has cut it down too much...altho it works if you are in a very high noise area such as a foundry or a concrete truck, I am now going to try dialing in 30k.

If this is the mic your using, I just tapped the black solder joint coming from the mic cartridge at the solder joint, soldered the black wire to the resistance lug of the variable resistor, and soldered another wire from one of the main lugs of the variable resistor back to the board. Being pretty careful not to over heat or splash any solder around on the board...
The resistor fits nicely in between the two up down buttons, and I run one wire down each side of the center of the mic.
I put a resistor in line on an Alinco mic several years before, and it worked well, so after finding no mods for this mic, I decided to do it again.

Hope it works well for you.

Don't see why they don't make a standard feature on all radios, that allows you cut back the mic in high noise level environments, as they did with some of the Cobra C.B.s years ago.

73
KC7MTN, Jim

Below are the voltages on the two SW lines:

Button        SW2        SW1
nil            5          5
UP             0          1
DOWN           0          2
1              1          0
2              2          0
3              3          0
A              4          0
4              1          1
5              2          1
6              3          1
B              4          1
7              1          2
8              2          2
9              3          2
C              4          2
*              1          3
0              2          3
#              3          3
D              4          3
P1             1          4
P2             2          4
P3             3          4
P4             4          4

The above voltages are rounded to the nearest whole number. ie the 0 voltage is actually close to 0.22v and the 2 volts is actually close to 1.95 etc.

The different voltages are developed by applying a resistor from each SW line to ground, the value determining the resulting voltage. The values in the mic appear to be 22k, 39k, 82k and 220k in a series chain. These resistors are pulled to ground through diodes in the case of the up and down buttons.

Transistors are used for the rest of the keypad buttons, presumably to keep the current through the condutive rubber contac pads to a safe low value.

This is why the resulting voltages are not exact voltages. The voltages are fed through 100k resistors in the control unit.

A complete remote mic and controller using these voltage readings should be able to be constructed so that it should be possible to remote control the radio using any of the available mic features. Not sure why you would want to but it would be an interesting project! You could remotely enter frequencies, memory selection, switch from one side to the other and so on.
Hope this information is of use to you all.

Grant, ZL2BK.
 

This modification will provide a push button to speed up the internal clock. By pressing the button, you can watch the time remaining LED's on the panel and select the amount of full charging time.

1. Unplug the charger for the AC power
   
    
2. Locate IC Q02, see drawing
   
    
3. Solder tack a 390 ohm 1/2 watt resistor and a normally open push button to Pins 13 & 15
   
    
4. Position the button switch in a handy position on the plastic case.

Caution - These modification have not been tested. The author, publisher and all other parties take NO responsibility or liability for any damage or violation resulting from these modification. Performing any modification may be a violation of FCC rules and will void the warranty of the radio. Use of any modified radio may be a violation of FCC rules. If you have any doubts, do not perform this modification.