Situation: Radio Shack wall transformer with 11 VDC unregulated output is
going into an LM371. I want to shunt with a pair of 5.1 V , 1A Zeners in
series
so that my adjustable output voltage is repeatable. Presently my Zener
series resistor is 180 ohms.

Problem.. I'm frying my zeners!!

What should I be doing differently?
======================
Would you please indicate where the 2 Zener diodes (in series) are located
in the circuit .
Before or after the LM317
If before the LM317 why ? The LM317 provides excellent regulation even with
fluctuating 'upstream' voltage.
What is the LM317's adjustable output voltage range. And which max current
are you drawing ?

Are you sure the zeners are 5.1 V,1 Ampere and not 1 Watt. If the latter is
the case the permissible current must not exceed 200 mA. .


For getting best reliability ,I would suggest you load LM317 with a current
less than 0.4 Ampere .
If more current is required use a 'wrap around ' PNP power transistor.
This is described and shown on page 1.15 of the book : Experimental Methods
in RF Design ,by W7ZOI,KK7B and W&PUA .

Frank GM0CSZ / KN6WH