|FT301 booster Unit Test procedure .. earl ve3ab 20 July 2015
|RF input from the FT301
radio or perhaps even
another rig but make sure
not greater than 10 watts
|hook this up with a short rg58 coax line
to a power meter and to a dummy load.
|First I would test the relay itself. The relay is activated by a 13.5 volt power source which is
active on transmit mode. For test purposes.. you could use a 13.5 volt fused at 1 amp line test
lead type hookup. Just toggle the relay on and off by touching plus 13.5 to pin 3. Perhaps
trace the connection to be sure you are on the right line.
Pin 4 is another 13.5 volt line which should be active on transmit. It provides the bias voltage to
the transistors during the transmit cycle. Maximum current should be only about 600 ma or so
so what I would do is run another 13.5 line fused at 1 amp and hard wire this to a 13.5 volt
power supply during the transmit cycle. Q1203 is the special type of transistor which tracks the
temperature of the final transistors and similarly regulates the bias to the transistors.
Pin 5 and 6 are the main power to the transistors. When the relay activates on transmit mode
then the power is connected through the relay contacts to the collectors of the final transistors
so what I would do is use a separate 20 amp 13 volt power supply and run a fused line to
pin 5 and 6. You can then turn on the juice to all the above connections
during transmit testing. Short bursts at first. FUSES very important when testing a circuit you
arent sure about. Best a fuse blows than a component in the circuitry.
SO HOOK UP A TRANSMITTER TO THE INPUT AND A WATTMETER TO THE OUTPUT AND A
DUMMY LOAD AND TEST THE BOOSTER UNIT. sHORT TESTS AT LOW POWER INPUT AT
FIRST THEN BRING THE POWER UP TO MAX OUTPUT.
IF NO OUTPUT THEN ITS TIME TO SEE WHATS WRONG ! BREAK THE CIRCUIT AT L1202
AND INSERT A CURRENT METER and try another test to see what kind of current is going
through at this point. IF there is no current then the transistors wont turn on properly and the
amplifer wont work. IF there is (about 600 ma or so current during transmit) or maybe a bit
more..then the bias is likely ok and you can then test the transistors.
You have to unsolder the transistors and pull them out of circuit to test their junctions with a
vom on diode mode to make sure the diodes are ok.
I probably have spare used tested matched pairs here at Earl Andrews .com
now (Netty Electronics). I would have to pull and test a pair.
feel free to ask questions I can draw some diagrams on this page for clarificaton.
73 earl ve3ab