Dave,
Be cautious with conclusions when probing with a 'scope probe in the 50
MHz section of the XV50. The probe can pick up RF and produce false
output indications.
The fact that you can induce output by probing C48 does normally
indicate that U6 and U7 are capable of producing a signal.
Check the LO signal. If that is good, then the problem may be in the 28
MHz bandpass or the mixer.
I am puzzled by your reference to 5mW. The K2 with the K60XV has 1mW
output - was that a typo?
If you want to probe the 28 MHz IF in the XV50, you can re-plug the
transverter for up to 5 watts input and you should be able to follow the
signal path through the 28 MHz bandpass filter - all the way to the
mixer input.
If it works with the high level input, then try the low level input
again - the 1mW input removes the attenuator and adds the gain of the Q6
stage.
73.
Don W3FPR
On 11/20/2015 11:22 AM, Dave Sergeant wrote:
My XV50, which worked fine for this summer's sporadic E season, has
suddenly gone faulty and has no output in either CW or SSB. The input
from the K2 is present, although of course 5mW is pretty hard to
measure accurately with my scope. There is also no signal at the input
of the power amplifier module, but if I connect my scope probe to C48,
at the output of the bandpass filter, and key the rig I have more or
less correct output and a good 50MHz sinewave on the scope - as soon as
I remove the probe the output disappears again. So the output module is
fine and the fault would seem to be related to the U6 buffer or the
bandpass filter. I am a bit mystified and need to sit down and work out
what is really happening.
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