Pete,
The most probable cause is that the power module is at fault. Re-check
the XV series construction manual to be certain the PA module is mounted
correctly with the right mounting hardware (in the right order) along
with the heat spreader and thermal pad. The back side of the module
must be in contact with the heat spreader, or it will throttle back power.
If all that is correct, then the PA module may be damaged.
If you can follow the schematic, then you can trace the problem at
several points while measuring the RF voltage with an oscilloscope.
There are some checks on the RF board that you can check to see if the
Local Oscillator is dropping in RF voltage (you can check that at a test
point with a DMM).
With an oscilloscope you can tell if the 28Mhz drive to the mixer is
dropping.
With great caution, you can also check the RF output of U6 (if your
oscilloscope and 10X probe is rated for 200MHz), but be careful not to
let your 'scope probe couple to the other circuits giving rise to
oscillation and erroneous conclusions.
73,
Don W3FPR
On 3/19/2018 6:41 PM, MW0RSS wrote:
Hi all
I have a used XV144 that loses power after a short time. I have tried it
with my K2 (using the KIO2) and also a couple of different QRP rigs, driving
it directly with a few watts. I have arranged jumpers accordingly, depending
on how the XV144 is being driven.
It completely loses power after a random amount of time. The power loss
seems unrelated to how much power the unit is delivering (the XV144 loses
power just the same, whether it’s giving 5W or 20W output).
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