Another long one. Sigh.
I sometimes wonder if the counterfeiters print the part numbers on their devices only after the big order is placed.
Some examples of what you may find locally.
2SC5200 and 2SA1943 from Screenvision. Total crap. Pops immediately. Package looks more like Fairchild/On-Semi parts, with a "shiny window" for the lettering. Toshiba doesn't do it like that.
MJ15003/4 MJ15024/5 from Communica. As above. Pops. See the link Norval gave. Same thing.
(I am aware that MJ15024/5 is a tricky one, because Motorola changed the die several times but not the number. Mix the types and kablooey. But if it's the real thing and you replace in batches, all is well. This is important for the guys with Phase Linear/Flame Linear gear who try to economise when the time comes.
2SB817 and 2SD1047 from Screenvision seem to work fine in their application (car amps and such), but I have no doubt that Sanyo never had a hand in these. The old ones were very different internally, and the packaging was never so crooked. The old ones had something like silicon gel (white) over the die on the heatsink tab, with the bakelite-like plastic over that. The new ones don't have the silicon gel over the die and the heatsink tab has sharp edges around the top that pierce mica washers. If you file those edges down, they work OK in small amps. YMMV!!!
Of course I'm in no mood to try and characterise everything I have to buy. Not that would I be very successful if I tried, as I know far too little about the technology. It's not just a case of voltage breakdown and current handling, one has to check if the gain seems reasonable over a wide BW, check switching times, monitor temperature while doing all this, and who knows what else.
What I do, is I break one open. With a genuine ON-Semi/Toshiba part, the silicon die cracks when you break off the black plastic. One part comes off with the plastic, the other stays on the heatsink. One can hardly chisel the die off the heatsink tab. With a dodgy part, the die comes off the heatsink tab cleanly. It may have been attached with Bostik. I think this pretty much covers everything from Inchange via Communica and the 2SB817/2SD1047s Screenvision has now. I presume that the silicon die was never attached properly. But I'm no silicon foundry expert.
With some fake TO-3 cans, if you cut the lid off, you can scratch the die off the heat spreader with a fingernail, if there is a heat spreader. Same with an unused one as with a dead one.
My solution was to get out of power amp repair as much as possible. Mostly because I did lots of PA stuff. Failure is expensive with many pairs, and it always happens on stage. Lots of bad vibes then. News of a good tech travels well, but news of a bad tech travels faster. Musicians like complaining at least as much as I do, but they add beer.
There's a little stash of genuine parts from EBV and Avnet Kopp just in case. Sold a lot to a friend who runs a repair shop. It may have prevented murder that week. For TVs, he's on his own. What I use from Screenvision (2SB649/2SD669) seems to work, but I doubt that it is genuine Hitachi.
It was never feasible for me to buy everything I need from EBV. Their prices are not totally unreasonable, I like them, but there are just too many different parts. TO-3, TO-3P and friends, MT-200 (Sanken) which they don't do, TO-126 and TO-220, some Darlingtons, Mosfets of all sorts, MJL21193/4/5/6 which they cannot source (yes, really, official agent or not). And you have to take quantity of them all. No telling when the broken amps will come by. With all the new SMT parts with unknown 2-digit codes, and manuals only for agents, not for sale, it just became a sh!t job.
Digidesign apparently wanted a non-disclosure agreement for the schematic of their charred mic amp full of SMT. So I just traced it out. Turns out it's no different from what Behringer have done slightly better for years. No different from everyone in the early 80s. Just the gain pot is a lot worse. But it's sacred knowledge. It's Digi. By the grace of God, it was an analog problem.
So now I'll be Mister Mixer Fixer for a bit. Till it too gets intolerable. When the fake TL072s and NE5532s come.
People say if you can't stand the heat get out of the kitchen. I intend to. But it won't make the kitchen any more liveable for anybody.
Because there's a buffet that needs replenishment out there. You see?