I recently had reason to look at the purity of the B+ supply voltage for my
Ten-Tec Titan amplifier. Not having HV measurement equipment, I hooked a scope
probe to the end of the voltage divider circuit which feeds the metering
circuit. The voltage measured by the scope was 4.8 V (representing the normal
2,200 V B+).
The disturbing thing I noticed however was a ripple voltage at 60 Hz (not 120
Hz as I would expect). This is from the output of a full-wave bridge rectifier
circuit with 8 X 400 uF of filtering. If I do the math the actual ripple
voltage works out to about 32 Vrms or 1.5%. I believe this is an acceptable
level of filtering .
Why is the ripple voltage a 60 Hz signal? I disassembled the PS unit and each
diode in the bridge circuit tested good, so I believe I am indeed getting
full-wave rectification.
Is the 60 Hz ripple I am seeing a result of transformer external inductance?
In other words, induced voltage from the 45 lb. Hypersil transformer on the
wiring in the power supply box? As a point of reference, I do not see a 60 Hz
ripple on the +28 V voltage for the logic and control circuits. It is provided
by a separate secondary winding on the same transformer.
Perhaps this ripple has been present since I owned the amp and I just didn't
know it. Short of magnetic shielding can anything be done about it? What am I
missing?
Comments/feedback welcomed.
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