Re: Tek SG505 Low Dist Oscillator

Kevin Oconnor

@Steve, Craig, Bruce

Yea, I saw that fixture in the SG505 service manual. (Thanks for the
reference). I might try

to build a limited version. But what you are saying is that the 333A
Wien-bridge rejection amp

has too many active components to get below .01% residual?

At the risk of being chastised for asking more about HP stuff here, my 333A
is prefixed 1137A, one of the

later models I think mid-late '70s?. Still that's ~40years old. Might I
expect that a lot of the capacitors in it are

beyond their time? Given that it is working as described, should I be
leaving it alone?


Fri Mar 24, 2017 4:19 am (PDT) . Posted by:

%20Oscillator> tss_steve_990

I concur with Craig Sawyers that your SG505 is just fine. The 333A is
not nearly good enough to measure its residual. A modern A/P analyzer
could probably do it, as well as the passive filter Craig mentioned, but
the 333A cannot measure with reasonable uncertainty anything lower than
0.01%. Its residual is just too high. In an ideal world you would like
the analyzer residual to be 10 times lower than the device under test
(SG505). The SG505 is so good, that it takes a really good, modern THD
analyzer to do that.

Steve Hogan

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