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Old 29th May 2013, 07:14 PM   #501
pdul is offline pdul  Denmark
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Stay away from semis in fleabay, that even smells like China
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Old 30th May 2013, 12:57 PM   #502
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i had a friend buy some RF transistors from ebay. these transistors were in a TO-5 can. the originals had the case connected to the emitter, the ebay fakes had the case connected to the collector (which is a bad thing to do for RF transistors, as all of that case surface area is capacitive).
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Old 12th September 2013, 11:19 AM   #503
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Quote:
Originally Posted by duder1982 View Post
There was a U.S. seller that was selling some matched pairs on the bay a while back, I wish I would have pulled the trigger for those.
US sellers aren't immune to fakes,
I bought two matched pairs of 2SJ74BL's from ebay seller QUA-CO who had a good story about these being the last of the genuine Toshiba JFET's from his known good stock. I bought these last winter and sat them on the shelf. Recently I pulled all of the Jfet's out that I have gathered and the ones from Qua-co did not look right. The stenciling was wrong and one of the fets had silver paint on the backside of it. I built up the little JFET test rig that Erno Borbely outlined in his 1999 Audio Electronics article and tested them all. The ones bought from Qua-co had a pinch off voltage of 1.25V and a transconductance of 11 mS, FAKES!

In comparison I also purchased a set of matched 74gr's from ebay seller Alweit and they tested with a Vp of .33V and a transconductance of 27 mS. I also have a few old J44's that I pulled from a mid-80's piece of electronics (without a doubt genuine NEC's) a few years back and they also had a Vp of .42 and a transcon. of 25 mS. I can highly recommend Ebay seller Alweit as I also tested the 170BL's and 170GR's that I bought from him and they have proper gain numbers in the 23 - 25 mS range with a low Vp of approx. .4V.

Lesson I learned, just because someone is from the US and gives you a good story about genuine doesn't mean that they are.
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Old 11th January 2014, 11:44 AM   #504
jitter is offline jitter  Netherlands
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It is time for an update of my answer in post #382 of this thread in which I wrote:

Quote:
Originally Posted by jitter View Post
At work I have seen thousands of the ON MJL1302/MJL3281 over the years. Without fail they have always looked like the top and bottom left transistors in your photograph right down to the font, size and position of the printing.

Normally I am careful not to judge by looks alone, but in this case I'd be fairly certain that the bottom right one is indeed a fake.
Some of the transistors manufactured by OnSemi have a different appearance with datecodes of 2012 and on. Genuine MJL1302/3281 (and possibly many other OnSemi transistors of the same shape) should now look like the MJL3281 in the attachment.
Compared to the "old" version, almost everything looks subtly different. They also seem to weigh a little less.
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File Type: jpg MJL3281AG.jpg (126.4 KB, 187 views)
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Old 11th January 2014, 02:59 PM   #505
AndrewT is offline AndrewT  Scotland
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how does that 504 pic compare to data released by ONsemi?
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Old 15th January 2014, 04:06 PM   #506
jitter is offline jitter  Netherlands
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Mechanically it conforms to the Mechanical Case Outline document. That document hasn't changed, though, it's from December 2004.
The datecoding system has changed from YYWW to YWW, where in the latter case the year is now indicated by a letter. C26 presumably means week 26 of 2013. This does not conform to the document.

The most striking differences are narrower leads (but spec allows for quite some variation: 0.93-1.48 mm) and the plastic body is no longer continuous near the leads but has "air gaps". The latter feature is not specified in the drawing.

A little correction to my previous post: 2012 can still be found "old style", the "new style" were on the market around the end of 2012. The very first I've come across had datecode B50 (week 50, 2012).
According to OnSemi, the MJL3281A is becoming obsolete (status: "last shipments", it's replaced by this MJL3281AG (status: "active").

Last edited by jitter; 15th January 2014 at 04:19 PM.
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Old 16th January 2014, 05:44 AM   #507
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i would be suspicious of any devices not conforming to the official marking specs. counterfeiters take advantage of the ambiguities...... that's why so many counterfeits are labeled with the last valid date code of a particular part number..... find out directly from ON if you can what date code transitioned from the "A" series, and the "AG" series so others won't get burned.
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Old 18th January 2014, 12:22 PM   #508
jitter is offline jitter  Netherlands
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I have no doubt that the new style MJL1302AG/MJL3281AG we've used over the past year (several hundreds) are genuine as they were acquired from an authorized dealer.

The last datecodes of the A-version we received were 1225. The first of the AG-version were B50.
The "new" datecoding system is now the same as seen on the smaller transistors (e.g. BD140, MJE15030 etc.), where there was already a single letter indicating the year.

These weren't the only transistors to change appearance, the MJE15030 and 15031 changed too.
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Old 19th March 2014, 02:00 PM   #509
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I recently bought 4x "2SA1124 PNP MATSUSHITA TRANSISTOR SC-51 -150V -.05A 1W ECB Transistor, Type: SI-P, Voltage: 150 V, Current: 50 mA, Power: 1 W, Frequency: 200 MHz"
from MCM Electronics. 3 of them yet correctly marked were NPN's!! Called customer service and they were happy to credit me for them, all $0.72, LOL! Of course, they don't carry them anymore. They were xrefs for c912 differential pair drivers in an old Kenwood amp I repaired. I know I should have replaced them both, but only one was noisy.
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Old 20th March 2014, 01:11 AM   #510
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that's rare, because MCM's parent company is Newark/Farnell, and usually they buy direct from the semi manufacturers.... unless they had those devices in some dark corner of the warehouse from before they were bought by Newark.... that was quite a long time ago, and before the time that counterfeits became a well known problem. there were lots of counterfeits floating around, but the problem had not yet been clearly identified.
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