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[Amps] 60 Hz B+ Ripple

To: amps@contesting.com
Subject: [Amps] 60 Hz B+ Ripple
From: "Wayne, W0ZW" <w0zw@fastmail.com>
Date: Sat, 30 Dec 2023 12:33:43 -0700
List-post: <mailto:amps@contesting.com>
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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