Stereomour Power Supply

[thdewitt]

OK, I am a beginner, but I am trying to track down some hum in my stereomour, so I am looking at the power supply.  The only thing I found that I though was odd is that Capacitor 1 on one side is 205Volts and it is 405Volts on the other side.  Other than that all measurements are the same for both sides.

I tried to take some readings with an Oscilliscope but not absolutely sure I am doing this correctly so I am going to add some pictures.

First, here is the first capacitor with the probe on it:
(https://dl.dropboxusercontent.com/u/38833957/Capacitor1.jpg)

Here is an AC coupled reading
(https://dl.dropboxusercontent.com/u/38833957/Capacitor1accouple.jpg)

Here is a DC couple Reading
(https://dl.dropboxusercontent.com/u/38833957/capacitor1DCcoupled.jpg)

Capacitor 2
(https://dl.dropboxusercontent.com/u/38833957/capacitor2.jpg)

CAP2 AC coupled
(https://dl.dropboxusercontent.com/u/38833957/capacitor2accoupled.jpg)
Cap2 DC Coupled
(https://dl.dropboxusercontent.com/u/38833957/capacitor2dccoupled.jpg)

Cap3
(https://dl.dropboxusercontent.com/u/38833957/capacitor3.jpg)

Cap3 ACcoupled
(https://dl.dropboxusercontent.com/u/38833957/capacitor3ACcoupled.jpg)

Cap3DC Coupled
(https://dl.dropboxusercontent.com/u/38833957/cap3dccoupled.jpg)


Does this look normal. 

[Paul Birkeland]

Cap 1 is in the middle of the doubler, and the trace will look good.

Cap 2 is after some filtering, and should be about right.

What does the scope trace look like when it's shorted? 

BTW - 1.5mV of hum at the speaker posts isn't particularly abnormal.