AU-555A Voltage select. What do you think?

[Robisme]

I had picked up this amp from the original owner. He bought it in Hong Kong.
When I power it up it hums for about 1 second and fades out. After about 10 minutes of listening I get a dc (I assume) voltage that makes the woofer pop.
After that it's fine. I was going to recap the amp, but figured I check a few things first. I checked the voltage selector plugs and found the main plug at the 117 volt position. Good. The sub V.S. plug, per the manual, should be set to the white position when the main plug is set to a white number. 117 is white. The sub plug was in the red position. This must have been missed when he brought it back from Hong Kong. Anyway, I moved the plug and powered it up. Now I get the typical woofer movement with no hum and I have not got the bad pop, yet. Do you (yee who is reading this) think the sub plug being in the wrong position could cause the pop? Also I think I am getting more volume with less distortion. Any thoughts?

Thanks.

Rob

 

[LBPete]

I have an AU-555A conected to my computer. It is as quiet as a mouse. No hum pop or whistle. If having the plug in the wrong position caused a higher output from the transformer, that could cause components to fail. For example, if the plug was set to 100v instead of 117.

- Pete

 

[Robisme]

The main plug was at 117. It was the small sub plug that was in the wrong position. I will look at the schematic to see what the sub plug changes.

Thanks for the input.

Rob