Date: Fri, 15 Mar 2024 16:44:37 -0700
Hi All,
We ended up fixing this issue after a lot of head scratching. It turns
out the 60Hz leak was not the main problem (more on this below), but rather
a fuse in the frequency synthesizer was blown, so we were not getting any
output from it. We didn't realize this because there is no indication
of power on this unit, and were unable to measure clean pulses or signals
from the transmitters or attenuator boards because of the 60Hz signal that
was leaking all over the frame.
Regarding the 60Hz signal: We started by replacing the ripple capacitors
as Gary and Dan suggested, and that did not change anything. We then
isolated each component, amplifier, etc in the case, but nothing solved the
problem. After taking out the internal AC->DC power supply out of
the unit, we noticed that the Earth/GND and Neutral wires were reversed on the
PSU (see attached pic). As soon as we swapped these to the correct
places, the 60Hz signal was gone. This was wired in this configuration
from the factory, and we've been using it as-is for the last 12+ years...
I suppose the good news here is that the rest of the electronics seem to filter
60Hz well :).
Hope this saves some trouble for others in the future. Thank you
all for your help and suggestions along this process!
Best,
Samrat
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