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Squarewave Linearity on HP 3310B Function Generator

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Daniel Gray

Jan 1, 1970
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Greetings all,

I have an HP 3310B Function Generator I've acquired (surplus), that has a
marginal square wave output. The wave shape looks more like a saw tooth,
with the leading edge taller than the trailing edge. Not having a book on
this little beauty, I was wondering if anyone might know if there is an
adjustment available for this characteristic, and if so, where it might be
found.

FWIW I verified probe compensation before viewing wave shape.

All other functions of unit appear fine. Sine triangle waves well defined.

Thanks in advance.
Dan Gray
 
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Dane Rogers

Jan 1, 1970
0
Hello Dan,
Believe it or not, I was the production engineer for the HP 3310B about
25 years ago (or there abouts). I am since retired but I might have a
manual around for the old beast. I'll take a look to see what I can
find and what I can remember. It's fun to see someone still using one.
I have one and still use it myself! I'll respond again in the next
day or so.
Dane Rogers
 
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Dane Rogers

Jan 1, 1970
0
Hello Again Dan,
Bad news! I have searched high and low and cannot find my 3310B manual.
Bummer! I worked on the 3310/3311/3312 function generators back in
the mid to late 1970's. My memory may be rusty but in general they work
the same.
The initial waveform that is created is the triangle and the sine and
square wave are generated from the triangle wave. The triangle wave is
generated with the use on an integrating operational amplifier with the
input fed by symmetrical voltage sources. The waveform frequency is
controlled by the voltage level (high voltage gives faster rise and
fall, therefore higher frequency) and the amplitude is controlled by
downstream amplification. The sine wave is formed by feeding the
triangle wave through a network of resistor dividers and diodes and
results in a fairly good sine wave (THD < -30db). Those sections of
your 3310B, are apparently working properly. The square wave is created
by feeding the triangle wave to a comparitor which switches according to
front panel symmetry controls. Your problem could be as complex as a
bad comparitor or as simple as a wire from the square wave button having
come off or shorted. This is a pretty old beast and if I were to place
a bet, I'd first remove the cover and examine the wiring around the
function select switch. If I find my schematics I could be more
specific but this is the best I can do until the manual shows up.
Dane
 
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