[Test-Equipment] Selective Voltmeter Diagram

[Hamel Family]

Has anyone a "similar or typical" Selective Voltmeter diagram?
I need to fix one frequency range of a Harmon 4200B Selective Voltmeter.
It arrived with a broken air variable trimmer capacitor, and the range using
it won't tune.
I guess it is just a calibrated receiver, but a block diagram would be
appreciated.
Apparently the company has been bought out, and the e-mail contact address
bounced.
Thanks,
Pat Hamel pehamel@i-55.com