[Amps] attaching a heat spreader to a heat sink

[Tom W8JI]

> Can you remember the frequency where the problem occurs?
>

No, but anyone building a solid state amp should always look 
at the drain or collector with a scope on every band. It's 
particularly important to do this when the device is near 
the peak voltage limit in normal operation. The Motorola 
boards I've worked with have always needed some 
improvements.

Lot's of people seem to only look at the DC rating and think 
if that parameter is met everything is OK. It's the peak 
voltage that kills the device, and if everything including 
the load and drive level is perfect the peak is about twice 
the highest dc value. Get a goofy strip line effect by 
pacing compensating caps on the transformer and nothing at 
the drains (or collectors) or filter leads or construction 
that unloads the output device at a harmonic and you can 
have some pretty high voltages compared to the drain supply 
voltage.

A voltage spike will kill the device instantly, unlike a 
thermal issue.

73 Tom