people..... look inside your amps
This is a really interesting amplifier with an interesting design and it is still available even in this parts shortage situation.
I saw someone suggested maybe the Yamaha R-S202 would be better, simply checking the promo photos of the main board itself shows it's nearly if not completely identical.
What immediately caught my attention on the STR-DH190 PCB:
That giant diode bridge right up against one of the big can capacitors marked "Sony" (very interesting itself!) is the mostly likely reason for these failures, so for when people like the OP try to push it outside of it's rated capacity just because "it still works" at the time, that extra power has to be output somewhere - heat - so those large can caps get heated and fail.
Same thing happens on TV's etc all the time - it's common design. No before someone starts yelling that it's a conspiracy to make your stuff fail, it's a very crude fail safe circuit for when things like prolonged out of spec usage like we saw in the OP post occurs.
(Companies producing products at this volume are conscious of costs at all stages and doing this instead of implementing, say a thermal fuse, costs way less. Plus if something is really causing it to heat up that much in normal usage then there is a problem anyway and this will shut it off and stop power from flowing into the device which is safer than potentially continuing to power a fault. Additionally if the warranty only applies for 6 ohms and up, then it doesn't have to be designed to withstand the temperatures reached driving 4 ohms, and could be denied warranty service... Just giving the manufacturers thinking on this sort of thing when you are producing 100's of 1000's of an item)
Of course i'm sure one could change those two large can caps to name brand ones meant to endure high temperatures like 125c or 135c, and give a bit of space between it and the diode there, toss a fan in the case (would be trivial) then you could run it at 140w 4 ohm all day, maybe even 160w with the fan in there.
no way you need a $50 fan, a PC case fan meant to between 5v and 12v is $10 at most and comes with screws, you can mount it under the vented part of the top case, just take off the top of the case and make some small drill holes then mount the fan on the inside and wire up the power to anywhere the 5v powering the front display panel is coming from, and it'll run slow enough that you shouldn't even be able to hear it without music playing. if it is mounted facing outwards to exhaust the hot air that is probably most efficient.
there are actually very nice name brand caps used from a good brand and series on the left side of the diode, where the important power filtering is happening, yet on the audio side we even see some no name caps used - i would love to try to replace all these with something audio grade like Nichicon Muse or Fine Gold or even just high grade caps like the United Chemicon used on the left side of the pcb.
of course a company like sony can manufacture their own caps but very strange of them to do so!
anyone have a yamaha R-S202? Main board looks almost identical. Would love to know what caps are used there instead of these "Sony" ones.
but if anyone still has a non working STR-DH190 in their possession non working & wants to get it looked at in usa, let me know, i would be interested to see if my hypothesis is correct, if so it should be easy to get up and running again, and maybe interesting to see how it measures again once all the no-name grade capacitors on the audio side are removed and replaced with good ones, wouldn't be surprised if some imbalance is due to some just simply being in poor tolerance
