Toriod 110 to 220V Conversion - diyAudio
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Old 15th December 2012, 07:21 AM   #1
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Default Toriod 110 to 220V Conversion

need some advice in converting my active speakers, Meridian DSP3100HC, from 110V to 220V.

The unit was from US and has been verified to work on 110V AC using an external step down transformer by myself. However, I would like to get rid of the step down transformer, if possible and easy.

The toriod is made by Toriod Audio Ltd in the UK. I failed to get any information of the toriod on internet. I uploaded the photos of the toriod here:
http://www.flickr.com/photos/53336639@N02/sets/72157632247444695/

The existing 110V connections of the input are:
brown wire - Live
white wire - Neutral
blue wire - un-connected
green/yellow - Ground

There are seemingly six output wires on the output:
orange x 2
yellow x 1
red x 2
black x 1

The above looks a bit unusual for me because it does not look like a dual 110V primary windings, which has four (or six for 100/110/200/220V) input connections. It does not look like a dual secondary output, which has four output connections.

I guess that I can change the unit from 110V to 220V by:
(i) disconnecting the white wire from the neutral connection on the circuit board (T11, photo #7); and
(ii) connecting the blue wire to the neutral connection on the circuit board (T11, photo #7).

The above assumes that the white wire is a 50% tap off from the Brown-Blue (220V) primary winding. But it seems uncommon because this design is a waste of wiring when being used in 110V mode. That is also the reason for dual 110V primary winding as far as I understand.

Grateful if anyone savvy could advise the verification procedure or provide your comment.

Thank you in advance.

Best Regards,
KC
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Old 15th December 2012, 07:46 AM   #2
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I think you are right to be sceptic - it would be a waste. It might be a winding for 10V though for 120V countries, that would be a relative small thing.

Your best move would be:

1 - get out the multimeter and measure all primary windings resistance (mains disconnected of course). This would give you an immediate clue as to the relative winding voltages;

2 - get out the multimeter and measure the secondary AC voltages going into the amp. If its a simple 2 x something, CT, chances are that the simplest replacement is a standard transformer with same core size and same secondary voltages, but with 220V primaries.

jan
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Old 15th December 2012, 07:49 AM   #3
Mooly is offline Mooly  United Kingdom
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Although what you propose seems correct this is something you need to be 100% sure on and so this is what I would do...

1. Fit a bulb tester (60 or 100watt filament bulb in series with mains).
2. Disconnect the secondaries.
3. Power up using your stepdown transformer.
4. Measure and record the secondary voltages.

5. Convert transformer to 220 volts.
6. Power up without the stepdown transformer and confirm secondary voltages are similar to before. The bulb should not be lit at all during these tests. If it does light then something is wrong in the connections. The bulb will protect you and the transformer if you get it wrong or its not suitable for conversion.

7. If all that is OK remove the bulb.
8. Remember to resize the mains fuse for 240 volts (usually around half the current rating of the 110 value and make sure its a time delay or anti surge type.

Good luck
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Old 15th December 2012, 08:10 AM   #4
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DON'T ASSUME ANYTHING - Measure and Confirm.

I would take the transformer out of the speaker and confirm the connections of the secondaries. It looks like you have two split windings X-0-X and Y-0-Y. This can be verified with a meter, 0-X and 0-X should be the same resistance. 0-Y and 0-Y also should have identical resistance.

Once you have identified the secondaries connect the known 110V connections to a 110V volt source and measure the voltages at the secondaries.

You can the try putting a lower violtage into one of the secondaries to see what you get at the primary windings.
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Old 15th December 2012, 10:02 AM   #5
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The resistance on the primary winding between brown and white is so low that my multimeter (Uni-T UT202) cannot read a stable and reliable reading. The resistance reading decays to something like 4 to 6 Ohm, but unstable. A similar unstable reading, 4 to 6 Ohm, was recorded between the orange to orange on the secondary winding; it is not zero Ohm. I confirm that the ohmmeter can read a stable zero when the red and black probes are in contact directly.

Measuring the open circuit voltages on the secondary, when the primary is connected to 110V, may give better information. However, there are 15 combinations on the 6-wires output.

Most of the transformers have only up to 2 secondary windings, as far as I know.

Any smart idea?
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Old 15th December 2012, 11:33 AM   #6
AndrewT is offline AndrewT  Scotland
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Use a bulb tester. If you are not prepared to build one then forget about ever testing this transformer safely.
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Old 15th December 2012, 01:24 PM   #7
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by caseykclee View Post

..............Measuring the open circuit voltages on the secondary, when the primary is connected to 110V, may give better information. However, there are 15 combinations on the 6-wires output.

Any smart idea?
The only combination that is relevant is how it is now... different combinations of secondary don't come into it.

If the primary is OK when rewired for 240 volts then all those secondaries will give approximately the same voltage output that they did on 110.

Two minutes of a job to check
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Old 15th December 2012, 02:42 PM   #8
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Well considering the secondaries you only have three questions:-

1. Are the YELLOW or BLACK centre connections ie 0V.

Easy to measure.

Firstly confirm that Orange to Orange is indeed one winding, then see if either Yellow or Black form part of that winding.

2. Secondly confirm that Red to Red is indeed one winding, then see if either Yellow or Black form part of that winding.

3. If neither Yellow nor Black are centre taps - are they one winding in themselves.
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Old 15th December 2012, 02:43 PM   #9
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AndrewT is jumping the gun a bit with his Bulb Tester - very important when connecting to the mains I agree but not important the way I am heading.
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Old 15th December 2012, 06:32 PM   #10
RJM1 is offline RJM1  United States
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The real mystery here is the Blue wire. For safety purposes I would hook up yor transformer line input wires ( the brown and the white wires ) to a 12V transformer and measure the voltages between the blue and the white wires and the blue and the brown wires and see if either one gives you 24 volts. Then measure the resistance between the blue and the brown wires and the resistance between the two wires that give you the 24 volts and make sure that is approximately double that of the brown and white wires.
If this is true, then you can hook up you 220V input wires to the two wires that you measured the 24 volts on when you connected the 12V transformer. Then hook up your 12V transformer wires to your new 220V input and make sure that your secondary voltages are halved.Using a dim bulb tester here would also be nice, but I'm not sure If we are allowed to talk about circuits that are connected to the mains power supply without a transformer. (Mooly?)

Last edited by RJM1; 15th December 2012 at 06:40 PM.
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