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Old 5th Feb 2017, 1:11 am   #1
Skywave
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Question BFR96 transistors: a quality problem?

Some time ago I built a 50 Ω in / 50 Ω out broadband amplifier using a pair of BFR96 in a Darlington configuration with a BFY90 to buffer the output. It worked very well: a gain of 20 dB (±0.5 dB) from < 1 MHz to 100 MHz. Unfortunately, I had a mishap with it, wrecked both BFR96 and found I had none left in stock - so I bought some more (usual on-line source). Now these replacement BFR96 have a different labelling on them: just the numbers '96' in very small and faint print. The originals were very clearly marked 'BFR96'. It now seems that these later ones don't have the HF gain as the originals did. Could I have been sold some sub-standard transistors? (They came from an alleged U.K source).

Somewhere, in the back of my memory, I think I've been down this road before - but I'd appreciate comments based on others' experiences, if any.

Thanks.
Al.
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Old 5th Feb 2017, 2:13 am   #2
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Default Re: BFR96 transistors: a quality problem?

If I'm buying on eBay, for example, I only buy where there's a non-library picture of the device with clear type marking, and preferably, a maker's name or logo and clear inference that is the device being supplied. Of course, this doesn't prove anything very much, but I won't buy from anyone who doesn't put up such a picture. However, there have been so many comments on the Forum recently about the extent of forgery that there must be some risk involved in buying from anyone other than the big-name suppliers.

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Old 5th Feb 2017, 12:08 pm   #3
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Arrow Re: BFR96 transistors: a quality problem?

Thanks, B. Re: your first sentence: in retrospect, that was the mistake I made. I used cost as the only criterion in my purchase decision. I now strongly suspect that these BFR96 are fakes - difficult to prove though.

Al.
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Old 5th Feb 2017, 12:13 pm   #4
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Default Re: BFR96 transistors: a quality problem?

I have just bought some 2N2222 from a "reputable" ebay supplier... they were the "A" version.. plastic case.. I looked up the connection data and were Coll, Base, Emitt as from the front. Put it in the circuit where I had used a metal 2N2222, which worked fine..the replacement had "0" gain... should have a Hfe of about 50.. just to make sure I put in another device,.... same.... even reversed Emitter and Collector....totally wrong, thus it had been connected correctly. I contacted the supplier via Ebay and got an immediate refund. The 2N4401's I ordered at the same time, work ok, but not sure about the spec. As you say Bazz.... buyer beware.
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Old 5th Feb 2017, 1:29 pm   #5
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Default Re: BFR96 transistors: a quality problem?

Actually, jellybean transistors like the 2N2222 seem to be the safest ones to buy from obscure eBay suppliers, because they are churned out in vast quantities and it isn't worth anybody's time to fake them. I bought 100 for 99p a while ago and they all test fine. Anything specialist is a much riskier proposition even from a legit UK distributor, though a big name supplier will usually refund or replace without problems.
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Old 5th Feb 2017, 2:31 pm   #6
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Default Re: BFR96 transistors: a quality problem?

I prefer to buy new old stock, the dustier the better. Less chance of them being counterfeit.
I wonder if transistors are not really fakes but other devices re-marked with numbers of more expensive ones?
But what constitutes a fake? What if they are just off spec rejects? When at Ferranti we could have as many bags of "rejects" as we wanted, they had all been through testing. Might have been borderline fails but we got badly plated cans and poorly printed ones as well though the devices were top line spec otherwise.
Do capacitor and resistor makers really test every one produced? Are they checked to be in tolerance or if a batch sample tests good and in tolerance do they assume all is well and accept the whole batch?
Can we believe that bandoliered components and SM as well are all checked?
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Old 5th Feb 2017, 4:32 pm   #7
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Default Re: BFR96 transistors: a quality problem?

As far as I know Sam it is "statistic analysis" they do... Batch test, then fiddle with the numbers...I used to QC TV's at various factories in the "near east" and I had an ISO list with the batch size and sample size, then from that a number of passes or fails. Say a batch of 1000 tv's.. the sample size would be say.... 128.... from that 3 fails.. the batch failed. Please excuse if I have the numbers wrong... its a few years since I did that, but the principle stands.
Paul.. you are right.... but my 2N2222's don't work..
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Old 5th Feb 2017, 5:27 pm   #8
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Default Re: BFR96 transistors: a quality problem?

Send me a PM if you want a few
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Old 5th Feb 2017, 11:45 pm   #9
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Default Re: BFR96 transistors: a quality problem?

Are you sure the original transistors were plain BFR96 rather than BFR96S? There is a difference in the biasing required if so.
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Old 6th Feb 2017, 2:16 am   #10
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Default Re: BFR96 transistors: a quality problem?

Originals were very clearly marked 'BFR96'. The replacements were described and sold as 'BFR96'. I am aware that the BFR96S has a lower gain: I deliberately avoided those, initially & subsequently.

Al.
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Old 13th Feb 2017, 10:32 pm   #11
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Default Re: BFR96 transistors: a quality problem?

Hi Al.

I think that I might have a few of these transistors 'pulled' from some equipment several years ago. I'll have a look tomorrow. If I can find them then you're welcome to them.

Regards
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Old 13th Feb 2017, 11:54 pm   #12
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Arrow Re: BFR96 transistors: a quality problem?

Thank you, Symon. I'll be watching this space . . .

Al.
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Old 14th Feb 2017, 10:42 am   #13
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Default Re: BFR96 transistors: a quality problem?

I've had a veritable ton of fake semiconductors over the last few years. I've stopped buying off ebay.

Occasionally if I need something obscure and RF, there are modern equivalents that are quite good, particularly when it comes to dual gate MOSFETs etc. Despite being SMD, they can be attached to a small carrier board easily enough and are usually cheaper on RS to buy 10-20 of them than to buy the original device on eBay.
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Old 14th Feb 2017, 3:26 pm   #14
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Default Re: BFR96 transistors: a quality problem?

Hi Al

I found the transistors which I've done a quick junction test on and they're all OK. The parts are made by Telefunken as they have TFK printed on them so should be good quality even though they're used. I'm not sure where I pulled them from. It's possible they came from a tuner of some sort possibly satellite.They are more than likely to have come from a European manufacturer, possibly Thomson.

Anyway PM sent.

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Old 14th Feb 2017, 3:30 pm   #15
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Default Re: BFR96 transistors: a quality problem?

That's a good tip Mr Bungle regarding using a small circuit board disc to accomodate the SMD dual gate MOSFETs. I think we're going to resort to doing this more as components with leads become more scarce and expensive.

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Old 17th Feb 2017, 12:47 am   #16
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Arrow Re: BFR96 transistors: a quality problem?

Time for an update.

Symon (Philips 210) has promised me a few BFR96: thank you, Symon; I await delivery; perhaps tomorrow. However, before that generosity, I ordered some more BFR96 from a different source and have replicated my cct. design using those. And the result? A nice flat response to 100 MHz - which the other 'BFR96' would not do.
As far as I'm concerned, that result is conclusive. However I will build another when Symon's arrive: I like to be thorough when investigating matters like this. (It's the engineer in me. )

And the moral? Be more careful when buying semi-conductors! 'Nuff said!

Al.
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Old 17th Feb 2017, 1:06 pm   #17
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Thumbs up Re: BFR96 transistors: a quality problem?

Symon: your transistors arrived today, Feb. 17.
Thank you.

Al.
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Old 17th Feb 2017, 3:21 pm   #18
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Thumbs up Re: BFR96 transistors: a quality problem?

Feb. 17th.: update 2.

I contacted the supplier of the original BFR96 transistors and reported my problem with those transistors. The response was positive: liability accepted; they had been mis-labelled! A full refund has now been received.

It's nice to have a happy ending now and again.

Al.
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Old 17th Feb 2017, 3:48 pm   #19
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Default Re: BFR96 transistors: a quality problem?

Quote:
Originally Posted by Skywave View Post
Symon: your transistors arrived today, Feb. 17.
Hi Al.

I am pleased that they arrived OK and hope they will be up to spec.

Regards
Symon.
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Old 17th Feb 2017, 5:13 pm   #20
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Thumbs up Re: BFR96 transistors: a quality problem?

"Up to spec.": your transistors are, Symon. I have just built yet another amplifier using them - and it works as designed and predicted. So that unreservedly settles the matter.

I don't think that there is anything more for me to say - except "Thank you!" to everyone who has helped me in this matter.

Al.
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