Popping off the top, one thing's for sure - plenty of "heavy metal" in here. That's a pretty beefy transformer, if i've ever seen one. That'll definitely put out the 500W into 4ohm it says on the back, with room to spare. For the more curious of you, the schematics can be found over at ElektroTanya.
Never heard of "Tm-HQ" or "KDC"(?) capacitors before. But then again, anything that says "VENT" on it gives me the willies...
Well, whoever's been in here before, sure was enthusiastic with the oil spray / contact-cleaner. I got a good whiff of "mechanical smell" (really "manly", har-har) even before popping the top off the case. That being said, nothing inherently wrong with that, you WANT the potentiometers to be nice and smooth, and as clean (internally) as you can get'em. Ain't no kill like overkill, eh?
Upon closer inspection of the rear board, i think i can start to see why the DI might've been acting up. Take a close look at this pair of caps. You seeing what i'm seeing?
Yup, a bit of a domed thing going on - that's never good. But then again, considering their "SWC" branding (ie. "no-name", likely some cut-rate Far-Eastern manufacturer), i guess it was only a matter of time.
Also, i'm pretty sure component legs are usually supposed to be silvery-looking, as opposed to... their current appearance, aren't they? The owner confirmed the unit had seen a bit of a water-drip while on tour, so that'll be the explanation for that. Nothing a smattering of fresh flux and a going-over with fresh solder over all the joints can't fix. That, plus a couple ChemiCon SMG 47u/50V caps to replace the stock ones (which were bloated on the bottom as well).
Right, with that out of the way, on to the fan. Doesn't sound particularly bad / unhealthy to me, in the couple minutes i had the thing on, but since "the customer is always right", might as well rip it out and see if i have some drop-in replacement. It's pretty filthy as it is anyway, so at the very least it could do with a proper cleaning.
That being said, one of the four bolts holding the fan and associated grill to the case was, for some reason, backed off about half-way, so there's at least the chance that some of the reported noise might've just been one or both just rattling against the case. On the other hand though, in for a penny, in for a pound - might as well swap it out anyway, considering its provenance and state, for peace of mind, if nothing else.
There we go, isn't that better? A nice NMB Flowmax (if memory serves, out of an older HP LaserJet printer), worlds above whatever bargain-bin "Xin Wang" might be. Seems to be a smidge louder than the old one, but on the other hand, also puts out quite a bit more airflow at idle too, so... Can't be TOO too bad, right?
Couldn't be bothered to remove the main power board and desolder the stock fan wires from the board, but the NMB's wires wouldn't have been long enough to reach anyway, so to split the difference, i just cut the stock wires around mid-way, and spliced them together (and insulated the white tachometer signal wire).
Signal tests showed the DI output to work about as well as could be expected, no extraneous noises or pops. I'm calling this one done.
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