18
User ManUal
v1.6
output, replace the IC.
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Check pin 14 of the 74HCT14 ICs for power. If none is present refer to the steps
in the previous section for absent 5V rail.
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Pins 11 and 13 of IC1 are the inputs of inverter gates, and pins 10 and 12 are
their outputs, respectively. If the outputs are not correct, check all
components downstream from it for soldering errors and other faults. In
particular, there should be a signal on the gate driver inputs if the gate driver is
removed. You can use this to check the state of the upstream electronics.
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If the gate driver’s output voltage measure between pins 1 and 3 of each IGBT.
The waveform should be as below. If it is not, make sure you soldered T2
properly and didn’t forget R1 or C8. If that is the case you have dead IGBT
gates and you should replace Q1 and Q2.
Once you have proper startup pulses at the gates of Q1 and Q2, connect your signal
generator to ground and the top of the antenna, and set it for a 0-5V 300KHz 50% duty
cycle square wave. You should hear the buzzing stop. Scoping the gates of the
transistors should give you the following waveform:
In the unlikely case that doesn’t happen, check your 15V rail—if it is not 15V you have
a damaged regulator incapable of outputting current. In addition, check D1 and D2 for
orientation, and IC2 for proper installation.
Gate driver output
Gate driver pin 1
Gate driver pin 2, 4
IGBT Gate *oscillation*
IGBT Gate
