On Wed, Dec 18, 2024, at 07:39 AM, Roland OE5ARN wrote:
I?m not a technician, but I made some measurements with help of the video from NA5Y.
The result: all is okay until minute 9:30.? The voltage on L10 should be abt 14 V in RX and close to ground on TX. This is not the case (only 0.25 V RX and TX). The following measurements are also incorrect. For instance R13 always shows 14 V (RX and TX). So I stopped testing.
?
Merry Christmas, Roland,
?
I went back and read your first post.? ?We may be looking in the wrong area.? The incorrect voltages on L10 suggest that there is a problem with the T/R switching circuit.? This could be Q4 or one of the components L10, L1,? L2, R10, or R11.? ?I would bet on R10 or L10 being open as those are the source for the receive 12volts on L10.? The next potential culprit is Q4 being open, as there is no voltage on L10 when in receive mode.? This would cause a failure to turn on D1 and D7, which connect the input and output RF to the amplifier stage.
?
Can you verify the voltage on the gate and drain of Q4?? This is a P-channel MOSFET, so the device is on when the gate voltage is lower than the source.? This happens when Q6 turns on.
?
73
Evan
AC9TU
