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Old 29th Nov 2017, 10:45 pm   #7
The General
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Join Date: Apr 2007
Location: Milton Keynes, Buckinghamshire, UK.
Posts: 329
Default Re: Hewlett Packard 200CD Wide Range Oscillator

Thanks for the comments folks - I was in the fortunate position of being able to upgrade some of my test gear so this is a replacement for a little Russian oscillator I bought a few years ago from a radio rally. I wanted a good one, preferably valve & I thought it was a great piece of industrial design.
Oh and it was built the same year I was born.
The lamps in the negative feedback loop are Bill Hewlett's patent which was used in HP's first product, the 200A. The HP lamp part number cross references to a GE part rated at 12V, 8mA. They do actually take 8mA at 12V but they don't light at that current of course. It seems they actually are the 250V 10W lamps stated on the schematic.
The output voltage is a bit too high for my needs so I'll probably build an off board switched attenuator as it's a little difficult to accurately set an output much less than 0.5V using its own rotary attenuator.
Cheers
Mark
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