[time-nuts] HP 105B power supply noise

Bob Camp lists at rtty.us
Thu Feb 25 17:33:30 UTC 2010


Sounds like the biggest thing you need is better ripple rejection. 

Without looking at the 105B schematic, I would guess it's going to have some
hard to find parts on it. If the board it's self is butchered that would
also be an issue. I'd vote for a modern replacement. 


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Ralph Devoe
Sent: Thursday, February 25, 2010 12:06 PM
To: time-nuts at febo.com
Subject: [time-nuts] HP 105B power supply noise

Speaking of low-noise regulators, I have an HP 105B standard that has
a burned up regulator board. The previous owner patched it up but it
still has about 50 mV of 60 Hz on the regulated 18.7 volt line. The 5
MHz output has a half a dozen 120 Hz noise sidebands when viewed on a
spectrum analyzer (an HP 3585a).

I'm trying to decide whether to repair the board or put in a modern
regulator. I'm assuming that I need better than 1 mV stability and
much less noise to get a clean signal. Any suggestions?


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