On Wed, 29 Aug 2007 17:57:08 +0200, "Peter Andersen"
put finger to keyboard and composed:

I have to NAD T762 on the table. Both with burned out (shorted) 5,1V
zenerdiodes (D718).



I have replaces them with a new 5W type instead of the original 2W.



But the diodes is getting extremely hot and I can't figure out if this is ok
(like the way it was designed). They are sitting directly in series with a
7812 from a 22V DC supply. The thought behind the design must bee to divide
the power loss between the zenerdiode and the 7812.

If there is a series resistor, then I'd measure the voltage across it.
That should give you the current, which in turn should give you the
actual dissipation in the zener. A 5V1 zener dissipating 1W would be
passing 200mA. Any more than that and I'd be looking for a culprit.

- Franc Zabkar
--
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