Proper mounting of TO-247 Devices

[Mark A. Gulbrandsen]

I am finally assembling my Aleph 2's. At this point I am in the process of wiring up the 6 heatsinks of one amp(2 groups of three) using turrett terminals that screw into threaded holes in the sinks. I really like these terminals and the ease of using them would cause me to consider building an Aleph using all point to point wiring in the future.
I began to wonder what the correct hardware is that IR reccommends....does anyone know.....? I am just using a standard 6/32 screw but shouldone use a cup washer, lockwasher or what? The Silicon insulators are only temporary!!
Thanks,
Mark

[MEnsing]

using turrett terminals

What are turret terminals? And where can you buy them?

I like the way you mounted the resitors by using terminals. I was also thinking about going point to point for my AlpehX. But I didn't like the idea that the resistors are floating and not mounted to something.

[Circlotron]

I like the idea of using a metal bar across the fet with a screw at each end and a piece of something soft between the bar and fet. That way you can put the pressure right where the die is in the fet, rather than using the screw hole which tends to pull down one end and make the other end that has the die come up a little. Have a look at the pics on this page http://diyaudio.com/forums/showthrea...5&pagenumber=2
They are hole-less TO-247's but you will see what I mean.

[Mad_K]

The metal bar mounting scheme is the best way ofcourse.. However, as long as you have adequate heatsinks and running the devices well within their SOA, I wouldn't bother.
I always use a flat washer and a springloaded one.



Here's some useful info: http://sound.westhost.com/heatsinks.htm

[Mark A. Gulbrandsen]

Thanks for the advice guys. Not sure if I have room to use a flat metal bar, but I am getting better heatsink pads and this may be one of the few Aleph 2's that is over heatsinked!! I am using two banks of these sinke per amp with two devices per sink.
Mark

[Nelson Pass]

I recommend a nice wide washer on top.

The TO247 case has good support at the hole, and you
just want to avoid cranking down too hard. We use
torque wrenches set at 8 inch-pounds.

[halojoy]

TO126 is one case you must not
put too much force onto, but yet a proper amount

[BrianGT]

Originally posted by Nelson Pass
I recommend a nice wide washer on top.

The TO247 case has good support at the hole, and you
just want to avoid cranking down too hard. We use
torque wrenches set at 8 inch-pounds.

Nelson,

Does the XA use TO-247 devices, or are you using TO-3 devices like x series?

I like the way that this is done:
http://www.passlabs.com/images/product/x250rail.jpg

--
Brian

[Nelson Pass]

TO-3, of course.

[Christer]

For those who are interested in some documentation on
mounting power devices it may be worth looking at Section 5
in http://www.onsemi.com/pub/Collateral/HB206-D.PDF
The document as a whole is about voltage regulators, but
the info on mounting of power devices is quite detailed and
should apply to transistors as well.