Norm Dresner wrote:


The circuit's input comes from the 25V AC on the backplane. Through the
diode bridge and the filter capacitors, we'd expect ~34 volts peak on the
input. Allowing for some high line voltage puts this at 37 or so. A
commercial grade 741 is only "guaranteed" to +-18V or 36V single supply.
The Tektronix schematics and parts lists indicate that U410 should be
"selected for +-20V supply" which more or less agrees with my calculation
and says that I'll need something better than a commercial grade Op Amp.

I don't have any MIL-grade 741's in 8-pin DIPs at the moment. I'm pretty
sure that some of the 14-pin ceramic DIPs I have are full range and could be
used if I make the space by replacing the 8-pin package by 8 pins of a
wire-wrap socket to raise the 14-pin body above the other components. I may
also have one or two 741's in 8-pin TO-5 cans that are better than
commercial but I'm not certain.

Go to mouser and order:

511-UA741CN or 511-UA741IN

They are made by ST, and sport a +/-22V abs max supply voltage.
The CN is a 0-70C DIP, and the IN is a -55-+125C DIP


-Chuck Harris