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33250A Bad Output/U1904/1NB7-8420

Question asked by Daveyk001 on Mar 30, 2017

I have a good sine-wave going in the final amplifier stage of a 33250A Function Generator.   The protect diode VR1902 was shorted.  The generator must have been hit with a high voltage UT Square wave pulser.  The output of U1904 is distorted with very little negative going signal.  I believe U1903 is bad also.  If I lift its pin #6, it puts out a straight 16volts all the time even thought it has inputs.  


U1903 is easy to get from Digikey, but not so much U1904 which is a custom Agilent/Keysight part and I am getting the idea that they won't sell it.  Why?  An entire board is something like $3300.  I can buy a 33250A, used, on Ebay, for $2200-$2500.  I would love to fix the one I had if I could only replace the final amplifier.


Thanks kindly,