Radio Shack HTX-100 Modifications

Frequency expansion

Remove bottom and top covers.

Remove the PLL board and tray that is held in by 2 screws on each side of the radio.

After you remove the board you will see a 4 sided surface mount chip IC 1208 that has 64 pins.

Look to the right of the chip and locate the 4th and 5th pins from the top right of the chip, pins 28 and 29.

Notice they are soldered together and run to a trace to a surface mount resistor.

Carefully cut the trace next to the 2 pins. Now locate 2 rows of pins to the top of the chip.

The bottom row last pin on the right has 5 volts DC on it.

Solder a 10K resistor to that pin and to the pins 28 and 29.

Now reassemble the radio and your done.

The radio will now tune 26 MHZ thru 30 MHZ.



Remove top cover of the radio.

Locate the 2 white wires running into the display light housing.

Remove the light and remove the green cover on the light.

Put the light back into the housing, you can wedge the wires in between the 3 electrolytic capacitors to hold the light in place.

Reassemble the radio and now your radio will have a light brown display like the big rigs.

Microphone wiring

Pin 1 - Microphone input
Pin 2* - Push to talk
Pin 3* - Scan down
Pin 4* - Scan up
Pin 5 - 8 Volts
Pin 6 - Audio out
Pin 7 - Microphone Ground
Pin 8 - Ground

* NOTE - Connect these pins to ground for function to work


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