Troubles with DUO 230

[Jani Tiainen]

My dear friend DUO 230 has started to be defective.

When DUO hasn't been used for a while, it works okay, but after a while
(20 - 40 minutes from start) it just blanks a screen and doesn't work until
cooled down...

Any ideas what might cause that? Also some times strange hissing sound is
coming out when it isn't working (but that is not happening always).

Jani "Rede" Tiainen