5MHz crystal

3mm LED, with leads and resistor

Updated frequency list & CTCSS programming instructions.

Remove top and bottom covers from transceiver and internal screening plates (if fitted)

Locate PIC microcontroller – large 28pin IC at front of main pcb.

Carefully remove the PIC from its socket.

Locate 4MHz PLL crystal. Note there are 2 x 4MHz crystals, the PLL crystal is on the left hand side between a trimmer and the PLL IC (TSA6057).

Carefully desolder this crystal and remove.

Fit the 5MHz crystal.

The LED is mounted in a 3mm hole to be drilled in the front panel.

Use a sharp 3mm drill; locate the hole midway between the SQUELCH and VOLUME controls and 10mm down from the top edge of the front panel.

Push the LED into the rear of the hole, and secure with a small blob of glue or sealant.

Route the LED wiring under the front edge of the main board; turn transceiver upside down.

Solder the blue wire to the ground land to the right of the PIC.

Solder the resistor on the end of the red lead to the 5^th pin from the top right of the PIC pinouts. This corresponds to Pin 10 of the PIC. Note there are no tracks connected to this pin.

Check that there is no solder bridge to adjacent pins.

Fit the replacement PIC module; check that its pins are straight and offer it carefully to the socket. The locating notch faces to the right.

NOTE: considerable force is required to insert the module; provide support to the underside of the motherboard, a small block of wood is suitable.

Power up the transceiver and operate the UP/DOWN buttons and check that the LED lights with alternate presses.

Changing the PLL crystal will upset the frequency calibration. Ideally use a frequency counter to monitor the transmit frequency; adjust the trimmer adjacent to the PLL crystal to set the correct frequency. A more tedious and less accurate method is to adjust for best received signal.

Replace screening plates and top and bottom covers.

NOTE: Level 1 modification leaves the receiver with the original 25kHz filtering. In many cases, this is of no consequence, but adjacent channel breakthrough is a possibility.

LEVEL 2 modification replaces the receiver filtering.

10.7MHz crystal filter (A)

455kHz ceramic filter (B)

47k resistor (C)

Desolder & remove original components; replace with new.

VERY slight realignment of the IF transformers may be required:

a) 10.7MHz transformer, located to the left of the 10.7MHz filter.

b) 455kHz transformer, located to the right of resistor (C).

Ideally these adjustments should be made using a signal generator and SINAD meter, but careful adjustment by ear should give satisfactory results.

NOTE: it is very important that the 5MHz PLL crystal is set correctly before attempting IF alignment (see Level 1).