Suggestion for Boonton 1120 Final Amplifier

[jackinnj]

This is the continuing saga of my spare 1120 -- the one with THD issues on the oscillator --

You might consider replacing the filter caps on the final amplifier board of the Boonton 1120 -- these were originally 100uF/25V I replaced them with 220uF/35V bypassed with 100nF Wima polypropylenes (mounted on the bottom of the PCB. When the board was placed in the Boonton box the THD+N% dropped by 0.01% -- still not acceptable.

There is a lot of noise in the box. An awful lot of noise. The oscillator itself measures 0.00099% to 0.00103%, it should be around 0.00030% to 0.00040%

The final amplifier, fwiw, measures around 0.00053% THD and it is pretty consistent from 20Hz to 50kHz.