Finding a replacement transformer for a Subwoofer

[jeroen94704]

Hello,

I own a subwoofer that I purchased when I lived in the US. Now I'm back, and I want to replace the transformer inside the sub so I can plug it in without a hefty 220-110 downconverter cluttering my living room (Also, the downconverter I used so far has died).

Is it enough to know the output voltage and power rating of the transformer, or are there other characteristics that I need to know before I can select a suitable replacement?

It's an odd transformer though, as it has two 110-inputs, and two low-voltage outputs. Everywhere I look fails to have transformers like that. Is it such an uncommon arrangement to have a single transformer with 2 in/output pairs? Where could I buy a transformer like that?

I am located in the Netherlands, but have no problem ordering it at a webshop abroad, as the shipping would still be less than buying a new sub.

Thanks in advance,

Jeroen

[Simon (Webmaster)]

Hi

Are the 2 sets of 110V inputs wired in parallel at the moment? Some transformers have dual primary windings, these can be connected in parallel for 110V or series for 240V. I think it would be safe to wire the 2 inputs in series to a 220V - 240V UK supply, but are there any markings on the transformer, or could you take a photo so we could double-check?

Also if the sub uses a captive mains lead (not a 'kettle plug' or similar detachable one) check the wiring colours - the lead should be be EU standard colours (brown, blue, green / yellow) and more importantly rated at 240V. If the lead is detachable simply replace the whole lead with a UK one, rather than simply changing the plug.

[jeroen94704]

Thanks for the reply. If you are correct, you just made my day .

Yes, the mains are connected in parallel (See pictures below). It's not inside the sub anymore, and there was a fuse in there, but the actual wiring hasn't changed. You can see there's two pairs of wires going into the transformer. The sub works when 110 [V] is applied to the red+black pair (through the white wire) and the red+orange pair.

2009-05-09 21.38.02.jpg (33.05 KiB) Viewed 7750 times

2009-05-09 21.38.17.jpg (34.5 KiB) Viewed 7750 times

There are no markings at all on the transformer that I can see, except for what I presume is a QA stamp, which says "QC6/OK".

If I understand you correctly, connecting (say) the orange wire to the black wire currently connected to the red wire, and then connecting the 220 [V] mains to the red and remaining black wire would do the trick, right?

Cheers,

Jeroen

[Simon (Webmaster)]

Can you clarify - are there 2 black wires, or is one brown - the picture doesn't show it well enough to be sure. The following assumes there are 2 blacks.

You should be able to connect the 2 primaries in series, however the windings should be in the same direction. The windings must also have been connected previously in parallel with both windings in the same direction, and since there is currently a black in each pair I think the 2 blacks will be opposite ends of each winding (one will be a 'start', the other a 'finish') - if you think of the 2 windings in a row the black wires will either be the 2 centre connections or the 2 outer connections.

Hence you need to join the 2 blacks together and connect the 220V to the red & orange. The fuse needs to halved in rating (twice the voltage so half the current). Check the output voltage with a multimeter before connecting it to the subwoofer. Also check the transformer is not excessively hot after it has been running for a while.

[jeroen94704]

Hi,

Apologies for not replying sooner, but I've only now had time to try your suggestion. And I'm happy to report this seems to do the trick! At least, when I wire the leads as you suggest, and apply 220 volts, I get the same voltages on the output as when I apply 110 volts with the original wiring.

I still have to connect the rewired transformer to the sub, but I'll report back to let you know the final result.

Thanks!

Jeroen

[Simon (Webmaster)]

Good news, that sounds promising. If you are getting the correct voltage I doubt you will have any problems when the sub is connected, but best check anyway (expect the voltages to be a bit lower once the sub is connected).