99% of you won't care about this thread. For the other 1%, lock the door and turn down the lights...I'm fixin to throw up some1967 precision porn in here. This is just a set of quick snaps I took before I closed it back up and turned it on. The good news is the oven is fully functional and correct. Bad news is I get no output on the 10, 100 and 1kV ranges. Since the reference works and is stable, there's really nothing that can't be fixed and that process will follow in the coming weeks. Worse come to worst, I at least have a backup oven for the 735A.
Brief history (or at least what I know of it or think I know)-The 741B is the cousin of the 740A/B, extending capabilities to include differential AC voltmeter. They both use the same ovenized voltage ref, which is also found in the HP735A DC Transfer Standard. A gain amplifier provides up to 1000V output. The AC input is provided via a permanently attached tweezer style probe. I believe this and/or the 740B was HPs final foray into voltage calibrators.
For now, sit back, relax and drool over something you probably won't ever see in real life.
Dirty talk...
Overview
God, please let those caps be good...
Reference Oven
Modulator/Demodulator...anyone spot the problem with it?
Range Switching
Pictures of individual boards and the precision divider to follow with the restoration/repair process.