Hopefull ps bad/burnt solder on a 2W ceramic resistor , double sided board
and soldering,
or not from the reverse side, the trace on the blind side, as obscured by
the resistor.
Anyone know of the SWPS schematic or is Citronic rebadged as other names?
The SMPS controller (seems to be outputs via a few predriver TO92 to 2x TOP3
powerFETs across the rectified mains) a SMD IR2156S which according to the
datasheet
is a flourescent tube electronic ballast and igniter, no mention of use as a
SMPS, with obviously no igniter requirement one hopes.
Anyone come across such as this before?

"American Audio" seems to be related to the Citronic name but exact cross
not found

It should have been a simple job. Intermittant drop out. Look inside powered
up and the ps fan is obviously defective, so fits the symptoms. Fit a
replacement and power up and not a dickie-bird. No led flicker or fan kick.
Undo the ps and obvious dropper solder problem underneath. Sort that out and
still nothing by monting on pillars. Checked for topside mixer and power
side earth continuity if that is required. So what else have I disturbed?
close inspection reverse-side looks fine, topside is heavily populated and
very few solder points can be seen. Continuity to the pa monitoring
thermistor good.
Enough power gets to the main bridge rectifier for startup supplies but the
relay does not click over that shorts out the droppers for full mains
current, let alone anything else.

This is a "Hailin switching power" DWP1070 power supply but that got me
nowhere.
From the IR datasheet Vcc is enough to get the controller started and both
control voltages are the right side of thresholds for operation so a mystery
why no oscillation.
The relay supply is taken back across the HV/LV divide, rectified from its
own winding on the switching transformer, so no oscillation , no relay click
over

I misread the datasheet , not enough Vcc for IC startup. Local vibration
from me must have been the camel's straw for a hot-side, luckily industry
standard voltage regulator once I could read the label, and its downside
electro, after having been cooked in service. Replaced and we have power
again. Now to take some quiescent DC readings on ps coldside and one of the
PA as there is nothing technical out there on these amps.
So fluourescent supply ICs can be used for controlling power amplifier SMPS
Tx

Probably the worst bit of "soldering" i've ever seen.
An intermittant fault with one channel speaker lines 2.7mm diameter over the
insulation, 1.5mm or so core, the 4 wires go to a rear board for speakons
and 1/4 inch outlets. Each wire is stripped neatly , leaving some whitish
thin coating over the copper core wires that probably holds the filaments
together until solder temperature melts it . Pushed through the large holes
in the solder pads and "soldered" on the blank side of the board with little
blobs of solder relying on melting of the board composite to hold in place,
and unmelted coating plainly visible on the other side. I assume the holes
are plated through or there would be no electrical connection possible. The
assembler must have soldered the wrong side.