Citronic Digi 16P mixer amp maybe 2007

"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.