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Old 25th July 2007, 10:59 PM   #111
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Yikes.
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Old 26th July 2007, 02:40 AM   #112
anatech is offline anatech  Canada
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Hi Jacco,
Obviously the work of nefarious people with good eyesight!

-Chris
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Old 1st August 2007, 08:19 AM   #113
sant_ka is offline sant_ka  India
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Hello, I recently bought 2 pairs of 2SC5200 & 2SA1900 in
Bangalore for Rs.180 (about US$4.30 ).

After checking this forum, I intially thought they
were fake on account of the price , but after opening
one of them, measuring their Hfe and Cbc, Cbe I think
that they may just be genuine indeed.

Can anyone please help me figure if they are real or
fake - I am mighty tempted to revisit the shop and
stock up.


2SC5200:

Cbe = 5.76nF, Cbc = 0.65nF


Ic (Amps) Hfe
---------------------------
0.0486 108
0.1698 115
0.2049 115
0.375 121
0.555 125
0.7425 126
1.02 128
1.254 127


2SA1943

Cbe = 5nF, Cbc = 1.153nF

Ic (Amps) Hfe
---------------------------
0.0522 116
0.1011 125
0.2124 119
0.555 125
0.825 124
1.119 123
1.242 120

The Cap values were taken on my DMM. Not sure of the applied AC voltage or frequency during measurement. The Hfe curve seems to fmatch the datasheet but I could not test above Ic = 1.2A on account of my power supply.

Here are the pics of the opened 2SC5200. The die is just under 5mmx5mm and looks similar to the original one shown on
http://www.yoreparo.com/articulos/el...ficados_2.html
(Search for "transistores 2SA1943 y 2SC5200" on the page)



Cheers,
Santhosh
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Old 1st August 2007, 09:52 AM   #114
AndrewT is offline AndrewT  Scotland
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Hi,
an electrical test to destruction would have been more informative.
1.0A into a medium heatsink and ramp up the Vce voltage, waiting for thermal stabilty and see how far into second breakdown the device could survive. Final temp measurement would allow comparison to the de-rated DC SOA. But too late.
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Old 1st August 2007, 06:01 PM   #115
sant_ka is offline sant_ka  India
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That's a neat idea. Would have tried it on one of the remaining pieces I don't have the right thermometer.

I was hoping that the Hfe values and the fact that it had a 5x5mm die could be used as an indicator. I don't think that a fake die of this size would show the kind of gain and linearity that I saw.

As a reference point, 2N3055 has a Hfe of about 90 at 1A.

Here are a few more pics of the devices

Regards,
Santhosh
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Old 1st August 2007, 06:31 PM   #116
sbrook is offline sbrook  Canada
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Well, one things for sure, with a 5mm square die, it WAS a power transistor die, and given that the idea behind the fakes is to make money by putting in the cheapest die they can get away with to show transistor characteristics with a fast check on a DVM, it wouldn't make sense to put in a power transistor die.

So, my bet would therefore be that it is probably genuine.

Find the transistor's hfe curves and if they are in the same ballpark as the values you pulled, then it's even more probably genuine.

For power transistors, look at some of the earlier examples in this thread ... the heatsink isn't cut cleanly and isn't ground flat ... two sure signs of a fake.
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Old 2nd August 2007, 05:43 PM   #117
sant_ka is offline sant_ka  India
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Yes, that's what I guessed as well. The Hfe values tally with the spec and the devices pass the cosmetic checks ( heatsink flatness etc).

Was just wondering if there was anything other obvious criteria/observation that I missed.

Regards,
Santhosh
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Old 14th August 2007, 09:55 AM   #118
ashwick is offline ashwick  India
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Quote:
Originally posted by sant_ka
Yes, that's what I guessed as well. The Hfe values tally with the spec and the devices pass the cosmetic checks ( heatsink flatness etc).

Was just wondering if there was anything other obvious criteria/observation that I missed.

Regards,
Santhosh
Can you let me know address of the shop selling these items?
Regards
Ashwick
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Old 17th August 2007, 04:49 AM   #119
sant_ka is offline sant_ka  India
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Hello Ashwick,

I am not sure if I can post a shop name on this forum. I'll email you the info instead. However you do not seem to have enabled email on your profile.

Regards,
Santhosh
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Old 7th September 2007, 07:55 PM   #120
K-amps is offline K-amps  United States
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Based on the picture Santosh, your 5200 looks genuine.
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