[time-nuts] HP 10544A with dodgy output?

Nick Foster bistromat at hotmail.com
Fri Jan 15 19:53:02 UTC 2010


Hi all,

I've just built a GPS-disciplined oscillator built around a 10544A, somewhat in the style of the Brooks Shera unit, just to use around the shack. Problem is, now that it's wired up, I notice the output is heavily distorted. It's clipped on the negative side of the waveform, like an emitter follower without enough headroom. The more I load the oscillator output, the heavier the clipping. When I load the oscillator output with 1000 ohms, spec for this unit, almost 30% of the waveform is clipped on the negative side. If I don't load it at all and just put a probe on the output, it looks OK, but still some flattening of the bottom half of the waveform.

I've got it wired up according to the datasheet, with +12V on the oscillator and +20V on the heater. The grounds for the oscillator/amplifier, oven controller, heater, and output are all tied together.

I know these are old units, and I'm wondering if this is a problem (for instance in the output emitter follower amp) that others know about, before I tear into it looking for a solution.

Thanks for your time,
Nick
 		 	   		  
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