TAIT T500 RADIO
First thing to do is put the radio on to the bench and look around to the bottom of the radio
and see the two recessed screws in the bottom of the set with the radio microphone
nearest to you you will see the screws about half an inch from the front panel, these can
now be removed from the radio these should be pozidriv and about 1/4 of an inch in
length, once these are removed ease the bottom of the radio at the front up slowly tilting it
backwards as the back will still be secure to the set in some grove set in to the heat sink at
the rear of the radio, now slide The bottom panel slowly forward and you should be left
with 2 wires still connected to the board Yellow and Black going to the Speaker remove
these very carefully remembering were they go. If the radio has a CTCSS board in it you
will see this to then left of the radio. Undo the screw holding this and ease the CTCSS
board up with your fingers and put on the bench as you will not need this board for this
conversion. To the front right of the set you will see a small board with lots of diodes on it
and you will now have to remove this board and looking at the truth charts decide with
frequencies you wish to put on your radio you will see that these are labelled (N9 8 7 6 5 4
3 2 1 0 A5 4 3 2 1 0) if you look at the truth chart you will see how to program these lines.
Once you have chosen the frequency's that you require and programmed the n code the
next step is to set the VCO and this can be done very ease as well what you will need for
this is your power supply and volt meter and dummy load and power meter. When
operating the Tait on frequencies below 150MHz, connect C204 (2p7) in circuit by shorting
the pads of LK-1
RX Alignment
1.
Connect power supply the radio making sure of the polarity before turning on.
2.
Connect the power meter and dummy load to the RF out put of the radio
3.
Now connect you Volt meter to TP2 centre pin and check for 4-volts this is situated
about 1/4 on inch behind this diode board you have just put back in to the radio.
4
You can now a just CV208 for RX 4 volts and this is the left one of the two
capacitors in the metal can just behind the test point and is marked RX and TX a
just the RX first and then go in to tx mode by depressing the PTT and a just CV210
for 4 volts as well,you will fine that power has come up very well to probably about
20-25 watts already.
5.
You can now check your tx freq and a just L30 which is situated to the front of the
radio under the diode board and can be adjusted through the small gap. Once the
desired freq is achieved you can now move on to the RX side of the project.
RX Alignment
With RX side you will now have to disconnect the power meter and dummy load and
connect a signal generator to the out put and set this for about 200rnV and adjust L19 L15
L13 L12 L10 reducing the sig gen as you hear the signal increase until you have reduce it to
about 0.1mV. You will need to go through this process several times until the desired
sensitivity is acquired and you’re happy.
Setting the deviation is not a problem as this can be done by adjusting RV79 to the left of
the radio a 1/3 of the way down.
One last thing I have not mentioned is there is a 90sec time out if you are like me and like to
waffle l this might be a good idea to leave this in place if you do wish to remove it then give
me a call and I will let you know how to do this.
Happy conversions from G0WFQ Malcolm
