Dave, in fact that's not new for me. We have had same growth, but much less. 
It's electrochemically vagabonded Lead from your solder through holes for 
heat transportation. Reason:
1. you have galvanic high potential difference
2. you have a high temperature
3. you have a high DC current to GND, which is wrong
You need look over the design.
/Inge


----- Original Message ----- 
From: "Dave Elder" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, June 23, 2008 10:00 PM
Subject: [TN] Power amplifier growth


> Has anyone seen anything like this?
> The growth is on a 100W power amplifier that has been sitting, powered
> up, under load, on a desk, for six months.
>
> Dave
>
> http://sites.google.com/site/taitpcb/
>
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