At least I know its safe , like the 300W ones, to swap L an R PAs,
confirming that a problem on the PA and not farther back.
I've previously tried on 300W ones visually comparing L and R amps to
find the extra transistor or trace . Everyone knows of the antiphase
output of the L one but where is the balancing inversion. Its on the
CONTROL3 board just prior to the PA header connectors, swapping of
signals to INV and NON-INV lines. So as far as I can find, despite
different identifying overlay labels on these PAs, there is no
electronic difference. Not sorted out what the CLK/CLOCK means as tied
to output_ground , with no connectors in the output 1/4 speaker sockets
anyway.
As cold DVM-D test comparisons of long-tail sections of each PA has not
shown up anything amiss, at the moment I'm assuming a transistor is
leaking a bit, especially as this amp is used outdoors. With +\-30V
bench ps powering, one section is off, will try 30V powering of the good
PA and see if the same with that one, no zeners around .
Then if the same I'll have to fudge my usual bench ps to supply +\-45V
by setting as isolated 30V & -30V with another single isolated 30V
supply bridging it along with a couple of 15V zeners, with fingers crossed.
I've decided its too awkward to try probing live, via the units ps ,on
all this SMD stuff, in an awkward position even with 5w power line
extender , having decided not to put droppers in there . It really needs
a test frame making up to hold these very light boards in place.