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are there counterfeit power rf transistors
Posted by
LaserTazerPhaser
on 07 May, 2019 11:11
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#1 Reply
Posted by
bd139
on 07 May, 2019 11:19
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#2 Reply
Posted by
Kleinstein
on 07 May, 2019 11:57
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You can get fake 0 ohms resistors and about anything fake that is more expensive.
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#3 Reply
Posted by
OwO
on 07 May, 2019 12:17
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In my experience very rare. For experimentation I would go for refurbished transistors salvaged from base stations. The price of $5 is about right for a refurbished part. I don't ever buy RF power transistors from a distributor because the prices are way too high for an experiment.
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#4 Reply
Posted by
bd139
on 07 May, 2019 12:26
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I'm not so sure about the refurbs either. I had a couple of Florida microwave attenuators off aliexpress and the tabs were cut short to the case making them useless and the case was badly chipped. Looked like they'd got them out with a hammer.
@Kleinstein: I've actually seen that a few years back. Before I decided to get some decent resistors I got a pack off ebay from China. The leads were like hairs and the 0 ohm resistor (single black band) was 10 ohms! Sure someone just said "eehhh, close enough!"
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The only way to get the genuine product for certain is to buy from Mouser, Digi-Key or one of the other part houses. Somewhere I read about how to spot a particular fake RF Mosfet - the lettering and company icon were slightly different and the leads were slightly different. I don't buy from Aliexpress but I always assume any branded electronic component I get from eBay is a Chinese fake.
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#6 Reply
Posted by
bd139
on 07 May, 2019 18:52
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They're not always fake. I got a batch of AD8307's that worked perfectly.
Chances of that happening is always 50/50 though.
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#7 Reply
Posted by
wraper
on 07 May, 2019 19:15
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They're not always fake. I got a batch of AD8307's that worked perfectly.
Chances of that happening is always 50/50 though.
Specialized things with custom pinout like that are not that often fake. But you cave a chance to get salvaged part with reapplied marking and/or "upgraded" grade. Things like opamps and transistors are a big no-no.
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#8 Reply
Posted by
bd139
on 07 May, 2019 19:26
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Yeah. It's not even worth it for that stuff.
The thing that makes me laugh with semiconductors is the inability for people to substitute. I saw someone at the local amateur radio club spend nearly £8 on a single MPF102 JFET because he trusted the seller (littlediode) and the design demanded that JFET. The circuit didn't work so I said have you tried any other types? Answer was nope it has to be an MPF102 as the schematic says it has to be one. After some persuading stuffed a J113 in it (£0.08 - 100x less cash) and it just worked
... The dude at littlediode is probably sniggering to himself that someone paid that for it while he's charging up his Tesla and all because of fear of substitution and fear of buying stuff from China.
Incidentally the MPF102 is so utterly shit and the device spread is so large that half of them didn't work in circuit anyway back when they were on the common market and you had to hand select them.
Actually I'm in the wrong business when I think about it.
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#9 Reply
Posted by
HB9EVI
on 07 May, 2019 19:51
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didn't have any problems with AD8307 from ali either; got some MRF196 as well, doing fine; but I already got fake high speed BiFet opamps; electrolytics are no good choice either from ali & co.
otherwise I'm ordering a lot from those sources - jellybean and special devices and I rarely have problems with them; e.g. I got PTFE N sockets for 1.50$ the piece; used to solder a semirigid balun with the 200W iron on it, no issues.
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#11 Reply
Posted by
HB9EVI
on 07 May, 2019 20:25
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it LOOKS genuine - if it is, you have to take a risk. I'll give it a try for that price.
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#12 Reply
Posted by
wraper
on 07 May, 2019 20:56
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How about these? https://www.ebay.com/itm/401750188937 Images show genuine packaging.
Chinese sellers usually sell not what on the pictures, those are just for reference.
They tend to charge more for listings which bare authentic part images yet ship out same fraudulent parts as those in the lower cost listings for the same parts.
Would like an RF power JFET preferably GaAs or HEMT for class A audio. Perhaps also for wifi amplification. There are lots of soviet transistors, those seem authentic. Has anybody tried those?
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#14 Reply
Posted by
David Hess
on 07 May, 2019 22:28
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I know they counterfeit 2N3904s and 2N3055s so they will counterfeit anything and expensive parts like power RF transistors are a prime target.
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#15 Reply
Posted by
mc172
on 08 May, 2019 00:10
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Yes. Try to find a genuine 2SC1971!
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#16 Reply
Posted by
OwO
on 08 May, 2019 04:01
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I have bought 2sc1971s from street vendors and even then all performed up to spec and I never found a defective one. Nowadays I don't use antiquated parts anymore so it's even less of an issue.
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#17 Reply
Posted by
CJay
on 08 May, 2019 09:59
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I'd be genuinely happy to find a source of 2SC1971 that work to spec and are cheap, how long ago did you find them and do you remember how much you paid for those OwO?
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#18 Reply
Posted by
OwO
on 08 May, 2019 10:18
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It was back in 2014/2015 and the price was 7rmb ($1.2) each. I just checked aliexpress and the most popular listing is $0.2 and has multiple reports of being fake, so I would be careful for this part number. Always read the negative reviews (1 and 2 star), a high average rating means nothing if there are lots of 1 star reviews. The taobao listings are around 10rmb now ($1.7) and probably have better chances of working, but there are also "refurbished" listings at around 2rmb.
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#19 Reply
Posted by
bd139
on 08 May, 2019 10:25
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I'm convinced there's no such thing as a cheap and good 2SC1971 now.
There are plenty of 2SC1969 left if you want HF only.
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#20 Reply
Posted by
OwO
on 08 May, 2019 10:32
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If you are just looking to build VHF power amplifiers then I would go for more modern cellular base station MOSFETs like the MRF9060MR1 or MRF5S9070NR1 (search M9060M and M59070N). They are usually refurbished parts and go for ~$3, but can operate down to VHF as well (internal matching becomes no-op at VHF) and are rated for 60W. At 12V you should be able to get around 10W.
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#21 Reply
Posted by
CJay
on 08 May, 2019 12:29
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I would want the TO-220 parts for refurbishing/repairing old equipment than building new, there is little point speccing obsolete parts for new builds so sources of reliable and cheap parts are always useful
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#22 Reply
Posted by
bd139
on 08 May, 2019 12:38
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Can't really win with that. Everyone knows that scarcity makes money now and what stuff is worth looking at ebay sold listings. Opportunities arise if you look at parts now. For example, about 25 years ago I saw a box of about 40 Eimac tubes for £20 at a hamfest. I just skipped over it. Meh tubes. Not interested in that. Now about 40-50 quid a go
I'm hoping IRF510 will go obsolete as I have over 200 of them
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#23 Reply
Posted by
CJay
on 08 May, 2019 16:19
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FQP13N10 for me, I've a stash of about 200.
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#24 Reply
Posted by
daedalux
on 09 May, 2019 21:23
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I think power RF transistors are the most counterfeited of them all. The TO-92 (small signal) and TO-220 formats in particular if the supplier is not reputable can be any crap, and many times you'll drive yourself nuts because the fake thing has the same junctions as the original and it could possibly half work for some random time.
Other packages may also be counterfeited, but most of the time they tried to build it and they may be working fakes or quality control rejections. Or it may just be the part code made to spec by some proper factory. Be very aware with any final power transistor for a transceiver, as they are on high demand for repair work at the lowest price.