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6 Posts
Discussion Starter #1
Have 1124 purchased in USA (rear sticker "100-120 VAC") ... Purchased in 2007
Have moved to a 240 V country and want to modify accordingly

Mains transformer inside has 3 wires on primary
Black - connected via on/off switch to IEC socket
Blue - connected to IEC socket
Red - not connected

Basically the primary is connected to 100V using blue and black wires

Question - anyone looked in side their 240 V version to ascertain which colored wires are used?

im assuming that the red wire is likely the different winding to change over to 240V mains input?
But the question - which of the black or blue?
Once again assuming it would be the black - which is wired via on/off switch

In other words - swap the blue and red wires (red to mains input, blue not connected) for 240V
Thus use black and red on primary for 240V operations

Anyone help please!

PS - yes I'm more than qualified to effect the change - with a little confirmation and comfort to above

2,454 Posts
I would contact customer support, they should be happy to explain what mod you can apply. Best to go straight to the source cause if you have a problem, you will still need them.

4,838 Posts
Agree with Tonto.

If you get no response, and you take full responsibility for your safety and that of your equipment, you can disconnect the blue and black, then measure coil resistance between all 3 pairs. It will be low, only a few ohms probably. Two of those measurements should be identical and one should be twice that value. Say for example (totally guessing at numbers):

black-blue: 20 ohm
black-red: 20 ohm
blue-red: 40 ohm

In this example, you would then know that blue-red, the highest reading combination, is designed for higher voltage input.

If your results are not obvious and clear-cut, do not rely on them.

I am assuming you are experienced working with dangerous voltages. 240V CAN KILL YOU! So can 120V, but it usually just bites you good. If in doubt, do not mess with it.

6 Posts
Discussion Starter #4 (Edited)
(Posted for benefit of any others with similar challenge)

Power transformer has 3 wires on primary
With resistance and useage as follows

Primary input windings
Black - blue 161ohms. Used for 110VAC (original configuration for USA sourced unit)
Black - red. 523 ohms. Used for 240 VAC. (Tested Ok)
Blue - red. 366 ohms. Useage?? Unknown

Secondary winding outputs
Green - green approx 19 VAC (varied between 19.2 and 20.2 volts when changing mains winding/input voltage)
White - white. Approx 10.5 VAC (varied between 10.3 and 11.0 volts ..)

Secondary voltage was tested with each winding (with plug disconencted from cct board) to ensure it maintained similar output to the
Original 110 VAC input configuration when converting to 240 VAC operation
Contrary to what is intuitive - the winding that is "double " the resistance does not produce the correct secondary output
Voltage (too high) ... And hence the much higher winding resistance actually produced the correct (unchanged) secondary voltage (as tested with
Voltmeter when disconnected from circuit board)
The useage of other input winding configuration is unclear and hence not used
Whilst this was not as expected ... It does indeed produce the correct secondary voltage, the unit is working,
And I'm happy!

....and during above modification, unit was also converted to 12 Volt DC relay trigger input (12 VDC coil
On a 240 VAC contact relay - in series with the mains switch) ... Which now enables unit to be switched
On via AVR 12 V trigger outputs (avoids "power on" thump .... Because it triggers prior to sub amp power up)
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