Advent Powered Loudspeaker and counterfeit transistors
 

Kudos to you Mark, and others, that are inquisitive enough to closely
examine faulty/counterfeit parts, and report the incidents.

The previous instances of fake components that I've heard about were
epoxy-bodied parts.. from the early PC cache-RAM that was just epoxy and
pins, to power transistors and audio power amp modules more recently.

So much for global trade. As distributors source components, they're rarely
certain about the quality anymore, and possibly more concerned with only the
cost difference of various sources.

I think the chances of finding fake components is more likely when they're
purchased from a mega-huge supplier like present-day MCM.
Fakes from smaller suppliers can happen too, because the fakes seem to be
getting into numerous supply chains.

Everything has changed with China as a mainstream source of almost
everything. Another aspect might be that there is always an abundance of
surplus and transporting it globally is fairly inexpensive.
So what does a guy do with 3 million excess empty TO-3 cases? Scrap value
might not be very much.

I don't recall hearing of fake components being found in ECG/NTE packaging.
As I'm sure you know, the cost difference isn't because of the individual
packaging in the plastic bag.

I've purchased some hardware parts (coaxial power connectors) from some
China sellers on eBay recently, and the poor quality is surprising.
The difference in quality is far below that of (RS) that shack store, who's
parts aren't anywhere near high quality (but some of their products are from
Taiwan, not China).

Chinese manufacturers can produce decent quality parts, but they don't need
to when their parts are found in supply chains (not that I'm saying that
eBay is a supply chain for reliable parts).

--
Cheers,
WB
..............


"Mark Zacharias" wrote in message
...
First, thanks to Chuck Hart for mailing me the schematics.

OK, well, there's this bi-amped powered loudspeaker. The tweeter amp is
blown.
The outputs are 2N6284 and 2N6287 Darlington TO-3 package transistors.
Pretty obscure these days. The schematic info also included NTE subs but
those were nearly 20.00 each, with no guarantee in my mind as to quality,
etc.

So I ordered the 2N numbers from MCM. More like 5.00 each and I've had
pretty good luck with MCM lately. When I received them, they were
mismatched
vendor markings, and one looked like cheap crap so I tested them right
away.
Actually, the one that looked like crap was OK, but the "2N6287" with
Thomson ST markings was SHORTED emitter-base right out of the chute. I
called MCM - "Oh, gee we're sorry" and they sent me another, no need to
return the bad one.
So I cut it open. It wasn't even a Darlington, just a single emitter base
junction and the die was only 2mm instead of 5mm. There was a visible gash
across the die, so obviously the thing was never tested in manufacture.

So I receive the replacement. I test it, and this one is OPEN emitter
base.
Once again I call MCM, got credit and no need to return them, so I cut
this
one open as well. Here's the fun part:

The transistor case was EMPTY. No die, no leads, just an empty case. I've
emailed pics to MCM.

With a little more research I was able to get the Onsemi MJ versions from
Allied, so all is well, and the repair worked out OK.

Those on the group using a binary server should see the pics. Anyone else
interested, I can email them to you.

Mark Z.