Onkyo SKW-540 hot transformer and amp

[tibimakai]

I have picked up from CL, this subwoofer for my home theater system(2nd sub).
It is working great, except when in idle(no signal) the back of the box is pretty hot.
I have opened it and the amp and transformer, is really hot to the touch.
I have plugged only the transformer into the outlet and is getting hot on it's own. What could be the problem? I don't hear buzzing, or anything weird.
It gets 2x60V input(from120V) and 1x 167V output. The transformer board, has only a fuse on it and two connectors(input/output).
Any help would be appreciated.


Tibor

[budm]

Re: Onkyo SKW-540 hot transformer and amp

Is it TOROID Transformer? Pictures?
Do you have a way to check the AC current draw of the transformer without having the secondary connecting to anything? Your DMM should be able to do it. It may have shorted turns.

[tibimakai]

Re: Onkyo SKW-540 hot transformer and amp

It is a regular transformer.
http://www.searspartsdirect.com/part.../0057/528.html
It is not connected to anything, jut to the 120V.
Actually the secondary output has two outputs, not the input.
It seems like, it has to deliver 2x56.5V(+/-) after is rectified.

[budm]

Re: Onkyo SKW-540 hot transformer and amp

So if you have just the primary winding connected to the AC outlet, it will get really hot? I would say that is not normal.
The secondary side is just a center tap winding feeding the bridge to produce +/- VCC to run the amplifier.

[tibimakai]

Re: Onkyo SKW-540 hot transformer and amp

I guess, it's not much that I can do with it, right?


Slowly getting back to the forum.
I have purchased my first house and I was and I'm still busy.

[budm]

Re: Onkyo SKW-540 hot transformer and amp

If it has shorted turn and the temperature get high enough to trip the thermal fuse that is taped to the winding of the transformer, then that will be the end of the transformer, I would not be comfortable using that transformer.

[tibimakai]

Re: Onkyo SKW-540 hot transformer and amp

I will have to pick up a new transformer.
Tomorrow I want to look into the amp section, because the heatsink it was hot as well.

[budm]

Re: Onkyo SKW-540 hot transformer and amp

You still should check the current draw in the primary winding without anything connected to the secondary winding. I am curious to know as how much current it is drawing.

[tibimakai]

Re: Onkyo SKW-540 hot transformer and amp

2.73a/ac

[budm]

Re: Onkyo SKW-540 hot transformer and amp

2.73a/ac

That is bad! I expect 0.1~.2 AC A at most.

[tibimakai]

Re: Onkyo SKW-540 hot transformer and amp

I thought so, that can't be good.
This can cause the amp to heat up as well?

[budm]

Re: Onkyo SKW-540 hot transformer and amp

Everything around it will be heat up from the heat radiate from the transformer, that is just the transformer without the secondary winding attached.
When you get the new transformer, you should set the power amp idling current as shown in the service manual.

[tibimakai]

Re: Onkyo SKW-540 hot transformer and amp

Bud, I'm thinking about searching for an aftermarket transformer.
What do you think that the output voltage should be, 2x 45V?

[budm]

Re: Onkyo SKW-540 hot transformer and amp

Bud, I'm thinking about searching for an aftermarket transformer.
What do you think that the output voltage should be, 2x 45V?

'It seems like, it has to deliver 2x56.5V(+/-) after is rectified.'
That means the ACV on secondary side of Transformer Voltage will be around 40-0-40.
56.5 * 0.707 = around 40VAC.

45VAC will give you around 63VDC
I do not know what the VA rating of the transformer is.

[tibimakai]

Re: Onkyo SKW-540 hot transformer and amp

I will measure the wire, when I get home.
Thank you, for the calculation, that is what I needed.

[budm]

Re: Onkyo SKW-540 hot transformer and amp

Is there any label on the transformer? You can estimate the VA by comparing the dimension of the old transformer with the new, it will give you some idea what the VA rating is.

http://www.achrnews.com/articles/123...ng-va-capacity
http://www.flanagan.com.au/basics.htm
https://yorkcentraltechtalk.wordpres...nd-va-ratings/

[tibimakai]

Re: Onkyo SKW-540 hot transformer and amp

The secondary wire's thickness, is 0.7mm.

[budm]

Re: Onkyo SKW-540 hot transformer and amp

That is only 21 gauge wire.
What is the dimension of the transformer?
I would say you will need 40V-0-40V 2A power transformer for that sub woofer. It is going to be expensive.

[tibimakai]

Re: Onkyo SKW-540 hot transformer and amp

Here is a picture.
I'm thinking, that $40 is not that much, for this transformer. I may just buy it, and be over with.

[tibimakai]

Re: Onkyo SKW-540 hot transformer and amp

Just a follow up.
Purchased the traf from Sears. First one got lost, but the second one, arrived all bend up(.
End result, it's working again and is not getting too hot.
Thank you, for those who helped.



P.S. I was out of the scene, due to buying my own house, but I'm getting back slowly. Not sure about TVs though.