Tait T500 Convertion Instructions

TAIT T500 RADIOFirst thing to do is put the radio on to the bench and look around to the bottom of the radioand see the two recessed screws in the bottom of the set with the radio microphonenearest to you you will see the screws about half an inch from the front panel, these cannow be removed from the radio these should be pozidriv and about 1/4 of an inch inlength, once these are removed ease the bottom of the radio at the front up slowly tilting itbackwards as the back will still be secure to the set in some grove set in to the heat sink atthe rear of the radio, now slide The bottom panel slowly forward and you should be leftwith 2 wires still connected to the board Yellow and Black going to the Speaker removethese very carefully remembering were they go. If the radio has a CTCSS board in it youwill see this to then left of the radio. Undo the screw holding this and ease the CTCSSboard up with your fingers and put on the bench as you will not need this board for thisconversion. To the front right of the set you will see a small board with lots of diodes on itand you will now have to remove this board and looking at the truth charts decide withfrequencies you wish to put on your radio you will see that these are labelled (N9 8 7 6 5 43 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 thenext step is to set the VCO and this can be done very ease as well what you will need forthis is your power supply and volt meter and dummy load and power meter. Whenoperating the Tait on frequencies below 150MHz, connect C204 (2p7) in circuit by shortingthe pads of LK-1RX Alignment1. 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 radio3. Now connect you Volt meter to TP2 centre pin and check for 4-volts this is situatedabout 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 twocapacitors in the metal can just behind the test point and is marked RX and TX ajust the RX first and then go in to tx mode by depressing the PTT and a just CV210for 4 volts as well,you will fine that power has come up very well to probably about20-25 watts already.5. You can now check your tx freq and a just L30 which is situated to the front of theradio under the diode board and can be adjusted through the small gap. Once thedesired freq is achieved you can now move on to the RX side of the project.RX AlignmentWith RX side you will now have to disconnect the power meter and dummy load andconnect a signal generator to the out put and set this for about 200rnV and adjust L19 L15L13 L12 L10 reducing the sig gen as you hear the signal increase until you have reduce it toabout 0.1mV. You will need to go through this process several times until the desiredsensitivity is acquired and you’re happy.Setting the deviation is not a problem as this can be done by adjusting RV79 to the left ofthe 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 towaffle l this might be a good idea to leave this in place if you do wish to remove it then giveme a call and I will let you know how to do this.Happy conversions from G0WFQ Malcolm malcolm.troy@virgin.net