On Sat, 26 Jul 2008 11:25:18 -0500, "KenB123" put
finger to keyboard and composed:

If the C33 is a tuning reference diode, then it would probably be more
precise than an ordinary zener.


Yes, it does connect to the tuner.

Ken

FWIW, my Sanyo set uses a uPC574J 33V tuning voltage reference. It has
a low temperature coefficient (+/- 1mV/degC) and low dynamic
resistance (10 ohms). If your set uses a regular 33V zener (which has
a 30mV/degC tempco), then I guess the design of its AFT circuitry is
such that it can pull the channel in over a wide range of
temperatures. I haven't had to look at a tuning zener for a long time
so I don't know which approach is used most often today.

- Franc Zabkar
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