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Old 8th March 2003, 11:54 AM   #1
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Question Leach amp transistors

I am building Leach amp and I want to use TO 247 devices and I do not know which to choose : 2SC5200 2SA1943 from Toshiba or
MJL 1302A MJL 3281A from Onsemi. Transistors from Toshiba are cheaper, but I am concerned about power rating 150 W instead of ONsemi 200 watts of disipation.

Since Leach amp produces near 300 W / 4 ohm I am not sure which to use.


Please help!!
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Old 8th March 2003, 09:53 PM   #2
Jeff R is offline Jeff R  United States
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Either would be fine from a power dissipation standpoint. The power rating of the amplifier is the power into the load, not the power dissipated by the transistor. Plus, it is pretty unlikely you will ever be operating at maximum power. Still, why skimp on a couple of dollars?

TO-247's are not as good as TO-3's in shedding power to the heatsink, so use care in how you mount the transistors to the heatsink.
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Old 8th March 2003, 10:16 PM   #3
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This may or may not be an issue, but there are a TON of surplus TO-3 heat sinks out there. I got the original spec Leach transistors in TO-3 cans. I am probably the only one on the planet who likes TO-3's. They have very low thermal resistance in the case, and swap out effortlessly. A solid stae tube socket of sorts...

Sheldon
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Old 10th March 2003, 04:37 AM   #4
djk is offline djk
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In addition to the plastic package having a higher thermal mounting resistance, the metal package is also rated at 25% more watts at room temperature. What is often overlooked is the maximum junction temperature for metal is much higher. All things concidered, I use twice as many plastic as I do metal for a given power.
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Old 10th March 2003, 06:41 PM   #5
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Thanks for reply.

What do you think, is it any electrical or quality difference between those two types (MJL1302 vs SA1943) ?

Supernet
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Old 10th March 2003, 09:56 PM   #6
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What about the ON Semi MJL21193/ 94 pair?
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Old 11th March 2003, 09:20 PM   #7
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Hard to get in my country.
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Old 12th March 2003, 07:43 AM   #8
swede is offline swede  Switzerland
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What country?

//magnus
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Old 12th March 2003, 03:59 PM   #9
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Slowenia!!
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Old 12th March 2003, 04:03 PM   #10
swede is offline swede  Switzerland
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Send me a sixpack of beer, and I'll send you some MJL21193/94 (plastic or to3, your choice).

//magnus
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