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Old 9th November 2011, 10:31 PM   #391
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Default Original jfet and mosfet

where can I buy original JFET and MOSFET manufactured by Toshiba, Motorola etc.
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Old 9th November 2011, 10:58 PM   #392
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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.
That fake one looks like I molded it in my garage, and like there isn't 20 Watts worth of die in there! The worst I've ever seen.
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Old 10th November 2011, 01:11 AM   #393
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Default fake alert...

some devices i've run across recently that are faked in large numbers...
SANKEN (SK logo)
2SD2390
2SB1560
2SB1647
2SD2560
MN2488 (made by sanken for sony) also 2SD2488
MP1620 (made by sanken for sony) also 2SB1620


these are darlington outputs used in the majority of mid grade multichannel A/V receivers for the last 10 or so years (Denon, Sherwood, Pioneer, Harmon Kardon, Marantz, some Onkyos). many of these parts can be quickly identified as fakes visually, but capacitance, leakage, Vbe, and beta tests are the best way to tell. these parts are flooding the market primarily through repair parts distributors. these are not really expensive or fancy transistors, but the sheer numbers of them being used in receivers seems to be the draw for counterfeiters to fake them. one of the largest dangers in using them is that they are a fire hazard. when the original sanken devices short, they rarely even smoke. when these fakes fail, they catch fire and emit showers of sparks (yes, like fireworks). if you see it happen it is quite spectacular. if it happens in a customer's home and starts a fire, you may have a lot to worry about.

while we're on the subject. if you are having difficulty getting a distributor to make good on selling you fakes, make them aware of the ramifications of these parts burning someone's house down. you may have put these transistors in, but you are small potatoes compared to a parts distributor.
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Old 10th November 2011, 01:18 AM   #394
Irakli is offline Irakli  United States
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Here is a very interesting article about counterfit electronic components in US weapon systems:
U.S. Senate Panel Targets Counterfeit Electronic Parts - Defense News

Disturbing news indeed.
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Old 10th November 2011, 01:53 AM   #395
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this is even more disturbing... just finished reading it...

http://www.eetimes.com/electronics-n...ply-chain-flaw
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Old 10th November 2011, 02:09 AM   #396
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Quote:
Originally Posted by daltvi View Post
where can I buy original JFET and MOSFET manufactured by Toshiba, Motorola etc.

you can buy ON (formerly Motorola) parts from Newark Electronics (or in other countries "Farnell")

i think you can find authorized distributors by looking on the manufacturer's web site.

for instance i did a price and availability search for MJ15024 transistors, and on the right hand side are links to distributors that sell them for onsemi.

Semiconductor Pricing and Availability

toshiba's web site has this:
Sales Contacts - United States - Toshiba America Electronic Components and Semiconductors
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Last edited by unclejed613; 10th November 2011 at 02:11 AM.
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Old 16th November 2011, 07:09 PM   #397
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Have anyone observed fake smallsignal transistors like 2sc2240/2sa970?
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Old 17th November 2011, 02:56 AM   #398
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since they are some of the most common small signal transistors used in amps that are currently being produced, i wouldn't be surprised. i average about 10-20 per week of each of these repairing amplifiers. for the 2SC2240, there is a korean version of this part, the KTC3200. the specs are IDENTICAL. the only problem is that the korean part has a high failure rate from C-E leakage. they also develop thermal problems. don't get me wrong, the KTC3200 has EXACTLY the same ratings as the 2SC2240, so technically, it's a valid replacement, but it's reliability is awful. my guess is that KEC licensed the process from Toshiba for making these transistors (KEC licenses a lot of semiconductor processes from other manufacturers), but Toshiba wouldn't license the part number because of the reliability issue. So KEC had to get a different number (3200 instead of 2240). i wouldn't be surprised if somebody is buying up KTC3200 devices and re-labeling them as 2SC2240.
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Last edited by unclejed613; 17th November 2011 at 03:01 AM.
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Old 17th November 2011, 03:37 AM   #399
anatech is offline anatech  Canada
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Hi unclejed613,
All these fake parts are really old news - really old. At least now the major distributors are taking strong steps to keep the fakes out of the normal supply system. These fakes actually became noticed in the TV repair business. I think the first large scale copy was the Sony SG613 SCR. I think I have that part number right. Anyway, the TV service field is strongly price driven and staffed by mostly uneducated (to the level required in other fields) service people. There is also a high rate of very low moral ethics and down right thieves. In this environment, fake parts couldn't help but to be an extremely profitable business. Back in the 80's, there were people in New York operating semiconductor labelling machines. They weren't manufacturing semiconductors.

As TV shops got more into audio service, and price pressures began to kill off service shops, this type of product became more prevalent. The early knock-offs were comical! How about a 2SD424 in a Motorola case that early 2N3055s came in. You know, the heavy raised bolt areas. These were immediately identifiable as Motorola parts. Then they started using the thin stamped Motorola cases (TO-3 style). TO-220 cased parts came next, but we already had horrible real parts (Texas Instruments made some nasty stuff back then).

For the most part, you could tell easily by the case. It is still a valuable thing to check. The lettering is another giveaway, and so is the manufacturer name. For example, in the past in the JIS system, a part number also signified who made the thing. An identically rated part made by someone else got a new number. Totally different from what happens in the JEDEC or Pro-electron system.

Buying from the least expensive source you can find also exposes you to an unreasonable risk concerning "remarked" (the proper term for this) semiconductors. Now to really muddy the water, a couple Chinese plants have opened that sell under their own name. They often produce discontinued parts, and I'll bet current parts as well. I can't speak to their quality, but I'd much rather be assured of top quality as my name goes onto each repair I do.

Hi tiefbassuebertr,
If you want to try and measure thermal transfer, be prepared for a lot of fun and a steep learning curve. Try measuring the B-E and B-C capacitance instead. Then measure the beta and any other easy spec to measure and confirm. The capacitance will give you some idea of the die size. Also map out the beta vs collector current and compare that to the data sheet.

For me, physical inspection and capacitance is normally enough. Anything else takes time, so a destructive test turns out to be less expensive (unless it's a pricy RF power transistor).

-Chris
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Old 17th November 2011, 04:03 AM   #400
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Default 2sc2240/2sa970

UncleJed613
Do you replace as many 2sa970 as 2sk2240 and do their KEC equivalents have poor reliability as well?
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