Help reqd - 115V PTX on 230V

[aardvarkash10]

OK, here's the thing. I bought three jukebox amps a little while ago. They are all ex-USA and have nice PTX in them, but wound for 115VAC primary.

We are 230VAC here in NZ.

After mulling it all over, I thought about doing this - half wave rectify the primary. Result (theoretically) is the same secondary voltages but potentially lumpy ripple.

Anyone see any issues?

[DigitalJunkie]

No,No.. You'll end up with DC half-cycles on the primary,which will make it very unhappy.It will saturate,and buzz and growl,before it starts releasing magic smoke.

[aardvarkash10]

you sure? How so?

[TheGimp]

Transformers don't like to be saturated. Dc Saturates transformers. Rectified AC is the equivalent of DC. Poof!

[TheGimp]

1) Get a 220:115 Auto or Isolation transformer and step the voltage down for the amp.

2) Buy a new transformer with the proper input and output and replace the transformer.

Or best yet.....

Send it to me and I'll run it on 115VAC... ;^}

[aardvarkash10]

The primary current is rising and falling - not DC as much as half wave AC. The only true DC component is when the diode is reverse biased, and then its no current at all surely... HTF can it saturate?

[TheGimp]

The average is DC. That is what counts.

[aardvarkash10]

nice try gimp! Tell you what, you come and get them. Bring some suitable toroidals (dual 115 primary) to replace them since you guys can get them cheap!

[aardvarkash10]

ok - I'm going to try it on a small PTX and see what happens... George-like reports back at you on completion!

edit - heres what I expect to see...

[DigitalJunkie]

I guess it may not release the magic smoke,but I think the transformer will buzz and run a bit hot,it won't be too happy.
It's a similar situation to mains with DC on it (a common problem with toroids in particular),and you'll actually be contributing to the DC on the mains..which may make other equipment unhappy.