Wow, do they have the inverter supplied from one long-ass fly lead, wired to the output transformer with another (the two red jumpers)?
Yeah, those things must switch slow as shit, to avoid any kind of overvoltage... there's no bypass cap near 'em either, at least not on top (and it seems unlikely they could afford a large enough ceramic on the bottom to be worthwhile).
Wonder if it's a TL494 / KA7500 on the riser board, or something else.
Looks like a current transformer and coupling capacitor (film) on the primary side as well, then also an aux supply (some ST? flyback chip?) and gate drive transformer. I doubt that means it's current mode in any meaningful way; more likely primary current is just used for latched faulting.
Transformer looks like they used extra layers of tape between P/S, but no margin tape; the windings go fully to the edges of the bobbin, probably having dubious creepage. Probably okay to use with grounded output, but for isolated SELV (needs reinforced type) I'd be suspicious. Besides all the other things to be suspicious of, I mean.
Also no litz wire used in the transformer, by the looks of it. So AC resistance will be pretty bad. Maybe it runs pretty slow (30kHz?), might not be terrible-terrible. Or if they used CCA, well...
Output has reasonable filtering I guess, nice big fat choke (is that a green/blue marking on the cores, so, #52 powder probably?), lots of positions for diodes but just the one I guess installed here (probably the top voltage rating in the family so that's fine; probably all populated for 12V, etc.?). What the heck is the white box thing (C25)?
No PFC on the input, so, 800W is all you're going to get out of the poor bastard before your breaker pops (expect PF ~ 0.5, 800W will use up most of a 120V 15A circuit), assuming it doesn't melt itself to pieces sooner of course. At least they have an NTC inrush with bypass relay, I guess? Think I see a thermistor elsewhere too, might be routed to a protection circuit or fan control. Of course with such insane losses, fan control is probably deleterious overall (better to leave it always-on so it's not cycling, risking getting stuck from the shite bearings also failing quickly?).
Tim