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Old 2nd May 2007, 09:54 PM   #91
sbrook is offline sbrook  Canada
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Very suspicious. I have some TIP41's and 42's purchased years ago and their hFE is around 40 which is what I'd come to expect. The hFE you describe sounds like that of a small signal transistor glued into a bigger case.
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Old 2nd May 2007, 10:12 PM   #92
Nordic is offline Nordic  South Africa
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could I use some resistors and set it up like a switch with a 40v 5A load (Ic), to see if it can handle that kind of duty in class ab... or can one not compare the 2 modes of operation...
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Old 2nd May 2007, 10:23 PM   #93
sbrook is offline sbrook  Canada
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If you have it on a heatsink that exceeds the thermal capacity of the transistor, then there's no reason you can't go towards Icmax in a class A config. If it's gonna die, that'll do it, just bias it up and crank the Vcc up watching the current.

I'm betting they'll go with an Icmax under 1A
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Old 2nd May 2007, 10:24 PM   #94
Nordic is offline Nordic  South Africa
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thanks will heat my hands over them in the morning....

Just thought of it, it is just a driver, so it will probably just see about 5 to 10W max....
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Old 19th May 2007, 11:55 PM   #95
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I have a couple of MPSA42's here of which I suspect contains fakes. I just finished a project which wouldn't work, which was caused because one of the transistors didn't work. And because the ones I bought today look significantly different than ones I had used before, I suspect they may be fake.

I have four versions:

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

The first one is the one I got today (the suspected fake), which has a silver front, which the other three don't have.

Also, the first one is the only one I have which has it's legs bent sideways like that. The datasheet shows an image where they are straight. However, if that would be an indicator, all of the counterparts to this one I have (the MPSA92), would be fake...

I don't understand why the second one is labeled KSP42 BTW, but that's what I got when ordering MPSA42's...

Could I be dealing with a fake one, or multiple fakes, here?
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Old 20th May 2007, 12:06 AM   #96
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HelemaalGaar,

the first one is original Philips manufacture, including the grey flavor.
There are at least as many different MPSA manufacturers as fingers on your hand.
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Old 20th May 2007, 12:14 AM   #97
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Quote:
HelemaalGaar,
Couldn't resist, could you

Quote:
the first one is original Philips manufacture, including the grey flavor.
There are at least as many different MPSA manufacturers as fingers on your hand.
I believe I have ruled out mistakes in the circuit, so I hope it was a normal DOA then. The transistors are part of a DC protector in a subwoofer, and I wouldn't want that to fail on me...
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Old 20th May 2007, 12:16 AM   #98
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Measure prior to leisure
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Old 25th May 2007, 10:09 PM   #99
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MY BDW94C


(left original ST)
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Old 25th May 2007, 10:37 PM   #100
sbrook is offline sbrook  Canada
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Look at the *difference* in those heatsinks!

The ones to the right, with the stamp can't be flat on the back! and look at the irregular top of the heatsink. They SCREAM FAKE!
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