Dual sinewaves?

[Ryssen]

I am messauring a 1khz signal trough a phonostage i bought on ebay.
But how come I get dual sine waves,I only use one channel on the scope.
Anyone...

 

[rayma]

The triggering is probably set wrong, try auto.

 

[Michael Bean]

Vertical mode is set wrong.

Mike

 

[as_audio]

It is hum.

 

[Refugee1]

It is hum.

Spot on.
Mains hum for certain.

 

[Enzo]

SLow down your sweep to see the 1kHz wave modulated up and down with the hum. As it is, your sweep is causing images at different spots in the cycle.

 

[Ryssen]

Yes I´ve listened to it and there is hum.
this is the best I can get turning the trigger.
If I push a button "X10 MAG" I get 1 sinewave,but its dancing arould on the screen.

 

[Enzo]

X10 is opposite of what you need. That expands the 1kHz wave and the dancing is the 60Hz modulation. SLOW the trace down and you should be able to see the 1kHz AND 60Hz components. it isn't a very practical way to view things for troubleshooting, but it should demonstrate what you are really looking at.

 

[as_audio]

50 Hz

This stage is probably without case or shielding ?

 

[Vovk Z]

If we suggest the oscillograph is working well, then that picture usually means an amplitude-modulated signal and the user chose a wrong synchronization (channel X) mode. (1kHz modulated by 50 Hz or something similar).