I've got the driver from a laser 'light show' unit here I'm trying to repair, and could use some advice. The driver connects directly to 120VAC supply and supplies (presumably--I've only glanced at the secondary side) a constant current to the laser module. Some time ago, the whole unit got taken overseas and was plugged in to a 240VAC circuit. There may or may not have been an appropriate transformer between the 240VAC circuit and the 120VAC device--I've gotten conflicting stories on that count--but for the sake of troubleshooting, I've assumed there wasn't.
And indeed, the input fuse on the driver board was thoroughly blown. Replacing the fuse revealed that the primary side switcher (On Semi NCP1014) was also blown--there's a tiny little pinhole through the top of the chip.
But here's where it gets interesting: the datasheet for the NCP1014 indicates it should be good for 700V--so connecting the driver to a 240V supply shouldn't have directly caused the switcher IC to go poof, right? Plus the primary components all seem to be rated for at least 400V--so despite what the manufacturer of the overall unit says, it looks to me like the driver should be good for 240V.
In any case, I can replace the switcher IC easily enough, but my concern is that the transformer might have been damaged as well. If that's the case, I'll probably have to toss the entire driver since, short of reverse engineering the entire thing, which I don't really have time for, I won't be able to spec a replacement. I'm measuring the DC resistance of the primary (when removed from the PCB) at 1.5Ω--Does that sound like a reasonable value, or low enough to possibly indicate a shorted winding?
I've drawn up a schematic of the primary side of the supply that I'll try to post tomorrow, but I'd greatly appreciate any thoughts in the meantime.
And indeed, the input fuse on the driver board was thoroughly blown. Replacing the fuse revealed that the primary side switcher (On Semi NCP1014) was also blown--there's a tiny little pinhole through the top of the chip.
But here's where it gets interesting: the datasheet for the NCP1014 indicates it should be good for 700V--so connecting the driver to a 240V supply shouldn't have directly caused the switcher IC to go poof, right? Plus the primary components all seem to be rated for at least 400V--so despite what the manufacturer of the overall unit says, it looks to me like the driver should be good for 240V.
In any case, I can replace the switcher IC easily enough, but my concern is that the transformer might have been damaged as well. If that's the case, I'll probably have to toss the entire driver since, short of reverse engineering the entire thing, which I don't really have time for, I won't be able to spec a replacement. I'm measuring the DC resistance of the primary (when removed from the PCB) at 1.5Ω--Does that sound like a reasonable value, or low enough to possibly indicate a shorted winding?
I've drawn up a schematic of the primary side of the supply that I'll try to post tomorrow, but I'd greatly appreciate any thoughts in the meantime.