Modification of 5-tone tonemodule TQ5004 or TQ5005 to a (1750Hz) singletone unit (repeater-call).
TQ5004 has a ZVEI tonecoil, and TQ5005 has a CCIR tonecoil.
The unit has two printboards, logic board and analog board.
For this modification we only use the analog board.
Layouts can be a little different around IC U106 (near the LED), see below.
But no problem, all components around IC U106 and the IC itself are removed, and diode D105 and Q130 as well ;o)
A few wires, a transistor and 3 resistors, and we are ready.
Tonefrequency is selected by connecting connector P3 pin 7,8,9 and 10 to either +8,5v (pin 13) or ground (pin 5).
If the unit is a TQ5005 selecting tone 8 will output 1747Hz, and if the unit is TQ5004 selecting tone 7
will output 1830Hz, and then a capacitor (4.7nF) parallel to C 113 is used to lower the frequency.
A transistor BC557 and 2 resistors are used to power the LED as a squelch-open indicator.
If a dual LED (red and green) is used, the red is used as squelch-indicator, and the green is powered by a resistor to +8,5v.
With power on and no signal the LED is green, and with signal the LED is yellow (see below).
