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PostPosted: 26 Apr 2010, 16:42 
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Joined: 17 Feb 2009, 10:28
Posts: 7
Hi everyone.

I just recieved Monitor Audio plate amp as a gift. YAY!... But the downside is, it doesnt work. My first plan of attack to fix 'er up ist to test all the connections before the transformer, seeing as this doesn't involve buying new parts. If this doesn't work, the next thing I am going to try is to replace the caps and rectifier in the power supply, then the transistors. But anyway, more to the point, there is a switch on the plate that allows switching between 120V and 240V operation. I am wondering if, at least for diagnosis, how to bypass the voltage switch. One big problem I have is that the first inch and a half of the wiring coming from the IEC jack, power switch, and voltage switch is covered in some thermal, non-conductive black goo, and therefore I cannot very well tell what goes where.

As for how the wiring goes, there is a white wire and an orange wire coming out of the IEC. The white goes to the POWER switch then to the transformer, and the orange goes to the VOLTAGE switch. Then coming out of the VOLTAGE switch are four wires: black, brown, and two new oranges. The order that they go into the transformer is, from top to bottom, White, Brown, Black, Orange1, Orange2.

I assume what is going on is that the white is a center tap in the primary coil, and to switch back and forth between 120 and 240, the current either goes to one side of the primary or the other. this leaves me with two main questions: 1) Why are there five wires? (The above situation would only need three). 2) How do I tell what is what on the transformer?

If you know what is going on and how I can go about fixing it, I would greatly appriciate some help. Also, if any of you experienced veterans of DIY audio have any advice for diagnosing problems in amps, and advice would be awesome.

Regards,
Alex


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PostPosted: 27 Apr 2010, 17:19 
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Joined: 28 May 2008, 21:53
Posts: 4586
Location: Winnipeg, CANADA
Alex, any chance you can post a photos or hunt shown a schematic?

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