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!!
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!!
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.
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.
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
Sheldon
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.
Thanks for reply.
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