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Jim, I recently bought a batch of GI856 high speed diodes. They arrived today, but they were shipped from China. Being as these diodes are discontinued, I'm concerned the ones I received might be counterfeit or fallouts. If you wouldn't mind, could you take a look at the photo below and let me know if yours carry the same markings?
Thanks!
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Buy Chinese. Bury freedom.
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"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
made in the US anymore? I thought most were made in Asia, Mexico, and some in Europe. No?
Steve
I'm not even sure.I like to give Jack a hard time because we actually think the same way.We would buy all American if we could and I do when it's out there.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Looks like it's not so easy to measure the Trr of rectifier diodes. Using a function generator (a technique shown on YouTube and other Web sites), the Chinese diodes measure roughly as they should. However, I have a number of general purpose rectifiers, including the lowly 1N4007, some old Archer parts, and even a few GE and Sylvania generics from the '70s. They all measure fast at the low current available from a function generator. Apparently, this test requires a high slew rate generator that can swing about 15-20V at 1A or so. The fall time needs to be about 20-30nS. I could probably build something close to these specs, but it's not worth the trouble for $30 worth of diodes. Incidentally, when I was hunting through my stock, I discovered a small pack of 20 GI856 diodes that I bought a few years ago. In fact, I think I bought them from Jim McShane. That's enough to take care of a few amplifiers until I find a good replacement.
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Buy Chinese. Bury freedom.
Congrats Sir! You'd just buried your freedom and becoming a pro at it while being socked by the Chinese at the same time.Rule of thumb is Never Ever Buy any obsolete parts from China / Taiwan / HongKong and all of Asia except Japan where authenticity can be confirmed.
Having said that, it might actually work fine with the reduced PIV, switching time, current rating; etc.
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.Thou shall not stand where I type for I carry a bottle of Certified Audiophile Air and a Pure Silver Whip.
Edits: 04/25/17
Hi TK,
Those are definitely not genuine GI diodes. The real Vishay General Instruments diodes have the part number including the GI characters - on the real ones they say "GI856" not just "856".
The diodes in your picture are discontinued ON Semiconductor products. Whether they perform like the real GI856s I don't know.
Sorry I can't pin it down further for you.
Well, I was afraid of that (not GI diodes). I noticed the ON symbol, but hadn't thought to look them up under a different number. These are apparently MR856 diodes, and they're not discontinued. Mouser has 10,000 of them at roughly the price I paid.
The MR856 is specified for the same reverse recovery time as the GI part, in fact "typical" is twice as fast (100nS). Other specs are similar, although junction capacitance isn't noted. I could measure the Trr and junction capacitance to determine whether these are Chinese fakes, but even if they meet the GI numbers, I wonder if they'll perform the same sonically. I was hoping to have the exact same parts because of your experience.
I ordered these through Amazon, so I'll lodge a complaint and see what happens. It's not worth the time or cost to ship them back, so I might end up trashing them. Good thing I only bought 60.
Thanks for your help with this!
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Buy Chinese. Bury freedom.
Is there a reason you wouldn't use them in a familiar design and listen to determine if sonic performance is as expected?
That takes a lot of time, measurements plus A/B testing. The purpose of buying these was to avoid the need to do that (based on Jim's use and online recommendations). In fact, I've already decided not to use these, so it doesn't matter how they sound. When I'm designing and building, I want to know that all the components are either from the West or from a culture where quality matters. I'm sure there are times that I unknowingly buy Chinese parts from a reputable manufacturer through Mouser or Digi-Key, but I can't help that. If they say "Made in China," I send them back.
I'll test the characteristics of one of these diodes as much as I'm able, in order to confirm compliance with the ON Semi specs. If it passes, they'll all go on eBay. If it doesn't, into the trash with the lot. There are plenty of 3A fast recovery diodes that aren't made in Guangdong.
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Buy Chinese. Bury freedom.
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