These radios were made for the Power Authorities who, until recently, used the PMR mid-band, ie mobile TX on 107MHz and mobile receive on 139MHz. With the coming of the expansion of the VHF Band II broadcast band to 108MHz they lost their lower frequency slot, so these and a lot of other equipment became redundant.

Part 1 - Getting In.
Remove the top and bottom covers from the radio. At the back of the set remove the 2 self-tapping screws that hold the top aluminium plate in place, also remove from this plate the 2 countersunk screws that hold the top boards in place, remove this plate. Some sets have a selective calling board fitted, this is indicated by the set having an extra thumbwheel switch on the front panel and a "CALL/RESET" toggle switch beside it. also inside there will be a larger board beside the long narrow synthesiser board. If the SELCALL board is fitted remove the 2 screws which hold it to the front panel and carefully lift it out as it has wires attached and lay it beside the set. The smaller board is the synthesiser board. Undo the screw that fixes it to the front panel and lay it beside the set as it also has wires attached.

Synthesiser Modifications.
Remove the four countersunk screws in the lid of the synthesiser box and remove the lid, also unsolder and remove the screening plate from underneath. Look at the layout diagram and remove C227 (39pF) and fit a 15pF in it's place. Also change C248 (18pF) to 12pF. From the junction of D202, R225 & C229 connect a 0.01mF capacitor in series with a 39k resistor as in the diagram below, also connect a 4k7 resistor to ground. From the junction of the 0.01mF capacitor and the 4k7 resistor connect a 12" length of screened audio cable with the screen connected to ground, feed the other end of the cable through the grommet in the front of the box. Solder the screening plate back to the underside of the board. Then fit the new EPROMS marked A & B in their respective sockets (pin 1 towards the front of the box).
This completes the synthesiser modifications.

Transmitter modifications.
If you once again refer to the layout diagram in the bottom LH corner of the board you will see (if fitted) a small PCB marked BRD2. This is the transmitter timeout board which is a bit inconvenient so may be unsoldered (3 connections) and replaced with link 5 as indicated on the main board. 
Next remove the cover over the transmitter PA, which is held in place with 3 screws along the side and 2 screws in the back panel.Now comes what is my least favourite bit. At this point I recommend you get a cup of coffee and study the layout diagram and the actual board as we have to change the value of 8 capacitors. The capacitors to be changed are listed below, and make sure you know their locations and in particular the tracks under the board. Use either solder braid or a solder pump to desolder the old capacitors, taking care as there is a screened lead running under the board which I found kept getting in the way. Replace them with the values listed below:-

C85 change to 12pF
C86 change to 47pF
C92 change to 12pF
C93 change to 47pF
C94 change to 12pF
C100 change to 47pF
C148 change to 47pF
C108 change to 10pF 
* *C108 is inside the can of L23, leave the can off for the time being.

Now remove completely the following components:-

C156 (27pF)
R107 (3K3)

Now change the value of the following:-
R103 change to 10K (If deviation still high change to 3K3 or 2K2.)

Now the coils to be modified:-
L14, L16, L17, L20, L21*, L22, L23, L24.

Carefully unsolder the coils one at a time, so you don’t lose their positions, and reduce the number of turns by one turn for each coil. Then re-solder each coil back into the board. I found it useful to slide something inside the coil when removing the turn, my trimming tool was just about right, but anything will do to stop the coil from getting squashed. *L21 on some sets is just a loop, if so, leave it alone. Replace the screening can over L23 The other end of the screened lead from the synthesizer should be connected to TP21, with the screen connected down to earth.This completes the modifications.

Alignment to 2M
Assuming that you have fitted the new EPROMS into the synthesizer in their correct sockets, as on the layout diagram, with their notches to the front. Make sure the boardsare safe and not touching anything, connect your 12 Volt supply and switch on. Select channel 20 on the channel indicator. Connect an AVO 8 or similar Multimeter to TP205 on the synthesizer board with the negative lead to the chassis or earth. Adjust the core of L203 carefully anticlockwise until the meter reads about 6.5 volts. Also check that the red LED near the front of the board is now out.
* !!!!!!! Ensure an adequate dummy load is connected !!!!!!!*
Then key up the transmitter and adjust the core of L201 anticlockwise with the meter still on TP205 until the meter reads 6.5 volts. Again, check that the red LED is now out. (This is the synthesizer "out-of-lock" indicator.) Adjust the core of L203 until the core is about 2mm out of the can. This completes the synthesizer tuning.

Receiver tuning.
Leave the channel set to 20, connect your meter’s positive lead to the positive end (the end with the stripe) of D18 (near TP8). With no signal this should be approximately 4.5 volts. Then connect a signal generator or similar to the ant lead tuned to 145.500 MHz and increase the output until the signal is heard. Feed more signal in until the voltage on D18 starts to fall. Adjust the cores of L1, L2, L3, L4, L5 and L7 for minimum voltage on D18, reducing the output of the signal generator as the gain comes up, and keeping the voltage on D18 above 3.5 volts. Repeat the tuning above again for optimum gain. If an oscilloscope is available connect it to TP8 and with the signal generator still connected to the ant socket with about 2.5KHz deviation tune T6 for minimum distortion. If a scope is not available connect an aerial to the antenna socket and go through the channels until a known good local signal is heard and adjust T6 for best quality audio. Set the mute adjust pot (RV6) so that the front panel mute control works at about midway, there is a bit of hysteresis on the control anyway, so don’t be too critical. This completes the receiver modifications.

Key up the transmitter and adjust L9 for maximum Now move the probe to TP16, key up the transmitter and adjust L10 and L12 for maximum. At this point there should be a slight output indication on the wattmeter, if not, put the diode probe near (or on if no reading) L16 with the transmitter keyed up and adjust trimmer C95 for maximum. Now you will have an indication on the wattmeter. Now tune C96, C98, C103, C104, C105 for maximum output. If this exceeds about 15 Watts turn down using RV5. These trimmers tend to interact so I advise going through the above sequence several times to get the optimum. As a word of warning it is fairly easy to get either the PA oscillating or an output on a lower frequency than wanted, check this with a counter with probe near the output. When I had this condition happen I found that the trimmers were screwed down. The correct position is roughly mid-travel, so repeat the above tuning and look for a second peak nearer mid-trimmer. When sure you have a nice output on 2M set this to 15 Watts with RV5 and seal the trimmers with quick drying paint, i.e. model enamel, or nail varnish, whatever is at hand. Then check the RF output and replace the screening cover and screw down, check the RF output again and quickly slightly re-adjust before the paint dries.

Then check the deviation with either a deviation meter or a friend on the air. This is set using RV4. If fitting a toneburst feed the 1750Hz into pin 32, the selcall input. If your set still had the original selcall board fitted it is possible to set this to send a string of "7’s" which correspond to 1748Hz, near enough for most repeaters. Remove the code plug PL401 and hard-wire the socket(SK401) as shown below. Cut the track below the board that runs from pin 20 of IC406 to pins 9/10 of IC408.

If the tone is off frequency link together TP408 and TP409. Connect a frequency counter to pin 32 (white lead), making sure you have a dummy load connected to the aerial socket, press the call button, the transmitter will key for a few seconds, then drop out leaving the tone going on the counter. This can now be adjusted with RV404. When set, remove the link and adjust the toneburst modulation level with RV403. The tone will now operate each time the call switch is pressed. On some sets you will have to remove link 401 to get results.