[TenTec] When is "hot" too hot?

[Tommy]

You will probably get a lot of different answers on this one Tim. I,
personally, quit, or better yet, put a fan on the heat sink if it ever gets
to the point it is too hot to hold your hand on  it. Reason being is that
one can normally keep their hand on something at about 50-55 C and can not
keep your hand on anything over that without suffering a burn. If the
heatsink is at 55C, think of the thermal resistance between the heatsink and
the power transistor junctions!! The transistor junctions will be at a
tremendous heat level. I designed microwave transponders for sattelite use
and it didn't take much testing to find out that heat is certainly one of
the main killers of semiconductor devices. A  totally inexpensive solution
is to use failed PC power supply fans permanently directed to move air over
the heat sink and use the +12vdc from the rig to power the fan.  It works!

Tom  - W4BQF

----- Original Message -----
From: <nz7c at cox.net>
To: <tentec at contesting.com>
Sent: Wednesday, July 14, 2004 12:42 AM
Subject: [TenTec] When is "hot" too hot?


> Please bear with this question.....as a rule of thumb from you guys that
have been around radios all your lives, how do you know when your rig is
running too hot? Don't laugh. For example, as long as you can hold your hand
on the fins of the heat sink is it OK - even if it feels pretty toasty? Or,
if you touch the fins and burn the crud out of yourself, is it time to quit?
You get the idea. Just wanted a little input :-)
> 73/Tim NZ7C
>
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