Antique Electronics and Vintage Solid State

HP 650A Output Divider Cable

65A-16D schematic

Someone on the Antique Radio Forum was asking about the HP 650A test oscillator. They are beautiful vacuum tube R-C test oscillators. The 650A was originally supplied with a Model 65A-16D Output Divider Cable, but they are invariably missing when you acquire a 650A.

HP 400C oscillation

I'm restoring an HP 400C AC VTVM. I've re-capped it, checked all the resistors, replaced the selenium filament rectifier, etc. I'm most of the way there. However, I started calibrating it and ran into a problem on the 100 volt scale. …

General Radio 1214-A Unit Oscillator

I'm working on a General Radio 1214-A Unit Oscillator. 

IMG 0533

The oscillator is fixed tuned but can be switched between 400 Hz and 1000 Hz.


It's a cute Hartley LC audio oscillator using a single 117N7GT as the rectifier for the transformer-less power supply and as the pentode for the oscillator circuit. …

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