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Old 10th January 2006, 01:27 PM   #21
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fwiw, Motorola hasn't made an audio power transistor in 6 years -- they spun off On-Semi to MOT shareholders in 2000.

it always make sense to check out the devices when you get them in -- and do your won QC -- even in a lot of several hundred MJ15003's and MJ15004's purchased from Avnet I found that there were several "duds" -- if you do the QC when you get them in you can get replacements from the distributor -- if you wait more than 30 days its "too bad".
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Old 10th January 2006, 02:30 PM   #22
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True, but the 21193/94 had been manufactured prior to the spin-off and even during. I QC'ed mine, they seemed ok. I opened a few and the substrate position and size seemed to be on par with the ON devices. Also they all came in a tray sealed from MOT/ON so I doubt AVnet had dropped a few duds (fakes?) in there.

However I must report,

However while I could gain match the 3's to the 3's (i.e. MOT's to the MOT's) and the 4's to the 4's i.e. (ON to ON), I could never get even a far off match i.e. the 21193's had a gain at 100ma of about 28 while the 21194's had a gain of over 100.

While I have been told it is not needed to match an NPN to the PNP (only like types should be matched) yet this difference to me was too much to ignore...

Any thoughts?
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Old 10th January 2006, 02:33 PM   #23
K-amps is offline K-amps  United States
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Quote:
Originally posted by jackinnj
they spun off On-Semi to MOT shareholders in 2000.
You mean Shareholders spun off MOT (the semiconductor division) to ON in 2000 (not the other way around) right?
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Old 10th January 2006, 02:34 PM   #24
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I have the same problem. I'll buy all my transistors from Farnell for my next amplifier. It's expensive, but it's not fake.
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Old 10th January 2006, 02:45 PM   #25
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You still need to check them... AVnet buys directly from the ON factory... and sells to retailers (not consumers like you and me), does Farnell do that?
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Old 10th January 2006, 03:51 PM   #26
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I think farnell only sells genuine parts, they are not crazy to sell fake ones...

Farnell isn't brazilian, look:

http://www.farnell.com/

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Old 10th January 2006, 04:08 PM   #27
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Nando, but you can buy from the Farnell's brazilian site.
www.farnell.com.br
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Old 10th January 2006, 05:21 PM   #28
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Eu sei velho !

FARNELL ROCKS
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Old 10th January 2006, 05:28 PM   #29
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Quote:
Originally posted by -_nando-_
they are not crazy to sell fake ones...

http://www.farnell.com/

No supplier is fully immune from contaminated distribution lines upstream. However you increase your chances by going with the bigger suppliers (Farnell may be one of them).

I have been told by some suppliers that they sometimes need to buy stock third party incase ON is out, so there you go... QC it yourself.
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Old 10th January 2006, 06:19 PM   #30
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FYI
Anyone's supply line can be polluted by a felon purchasing, and then returning a large lot of parts to a reputable distributor.

The felon's fake may even have the same markings and lot code as the originals, causing the ditributor to trust the return.

To QC a purchase non-destructively, you may need to put together an SOA jig. This applies simultaneous voltage/current to the part which brings it just inside the SOA curve of the original.

You're looking for a region in the SOA which the original can sustain, but a fake cannot. You may need to test several points on the SOA curve for confirmation. Once you've got the jig set up, you can test many parts quickly.

A powerful, var V, var I power supply is handy for this...

Wear safety glasses, and have the fire extinguisher ready.

Joseph
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