Vectronics VEC-1402K - Manual (Page 17)

VEC-1402K Instruction Manual 2 Meter Pre-Amp Kit
15
IN CASE OF DIFFICULTY
Preamp Stops Amplifying:
A working preamp that fails "in-service" generally indicates a failure of
transistor Q1. Other things that should be checked are the supply voltage and RF
cable connections. If the preamp failed after being installed in a transceiver, it
might be due to excessive transmitter RF “leaking” back into the preamplifier
and damaging Q1.
Cannot Align or Test Preamp:
A newly constructed preamp that fails to work requires a careful recheck of all
work. Low gain, or inability to properly tune the preamp may indicate damaged
capacitors, an improperly wound coil, or parts in the wrong positions on the pc
board. A preamp that operates intermittently may have poor solder connections,
a problem with coax connections, or an intermittent connection to the power
source. Instability, or self-oscillation, may be caused by RF-cable problems, or
by excessive component lead lengths on the pc board.
Voltmeter Checks:
With 13.8 Vdc applied to the preamp, the collector voltage on Q1 should read
approximately 9 V, and the base voltage at .76 V. These voltages are easily
measured at the opposite ends of 100-k bias-resistor R1.
If technical assistance or factory repair is desired, please refer to the warranty
instructions on the inside front cover.