kiev wrote: Howdy Mike, welcome to the miev forum.
Hi. I may be starting an interest in iMievs, for a colleague.
I was thinking those blue caps were like the 2 Y caps of an EMI filter such as this: ... and it read: HR R 102k
Yes, that clinches it. Now I'm thinking that electronpusher's "resistors" may have been surface mount versions of those Y capacitors. They all look much the same when burned. Is this possible, @electronpusher ?
With the chargers seemingly so voltage agile, I can't see any reason for resistors in one model and capacitors in another. Maybe they changed the circuit, perhaps for reliability problems. So I agree that swapping the bottom board should be ok. Weird that the mains conditioning is on the DC-DC board though. I guess it's just where it fitted.
Edit: some more thoughts. It looks to me now that both the charger and the DC-DC are on the bottom board. That's why the mains goes there. The mains comes in on two orange wires (with active marked as black, the US convention, and strange to we Aussies where black usually means neutral), and the charger output (to the battery) goes out on the other two orange wires at the bottom of kiev's photos. There is a green there too (hopefully with a yellow stripe) that goes to ground/earth/chassis.
So the top board seems to be all control logic, plus half the mains conditioning: fuse, surge arrestor, X capacitor and bleed resistor (which doesn't seem to be visible under the potting, but you can see its symbol under the PCB), and three movistors (MOVs, Metal Oxide Varistors, which are voltage dependent resistors, basically more surge protection). The surge arrestor appears to be in series with two of the MOVs, one each to active and neutral. So actually, electronpusher, there is a fair bit of protection on the mains side. I'm moderately impressed. The potting seems to be to keep dust and grime (even though this box is probably sealed) from making paths for the higher voltage, and to keep high voltage parts and tracks away from fingers. It also has the effect of mildly frustrating repairers, but safety and longevity are obviously more important. Electronpusher, does your surge arrestor (designated "SA" on the top board) look as-new as does Kiev's?
Another thought: perhaps "soot from resistor" is actually arc flash from inside. I've seen this with Elcon chargers. Is that possible?