transformer meltdown

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I have 18-0-18 transformer and power to my LM3886 P2P amp. Prior to Lm3886 P2P I was using this for tda2050 mono. This transformer I was using from last one month and everything was fine. This time I decided to build TDA2050 multichannel amp. (Picture attached) First, I build single channel & test again everything was fine clear tone, no hum, no distortion etc., then I build another three channel & tested I found lot-off distortion & found IC becomes very hot. And I use white-grease then I found distortion becomes low but not clear tone. AND SUDDEN MY TRANSFORMER STARTS SMOKE. I SWITCH-OFF POWER SUPPLY AND FOUND IT WAS VERY VERY HOT & MELTING.

What is my mistake. Please help me. Attached pictures are not very clear SORRY.
 

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My guesses are one of the three channels had a bad chip/was miswired or in the process of adding the three channels you somehow shorted the rails. Clearer pictures would help diagnosis.

Your transformer is dead - most likely an effect rather than a cause of your problem rather than the cause. Replace it.

Test each channel individually when you get another transformer. You might want to use a 100R 1/4W resistor in each rail to act as a current limiter (and really slow blow fuse) when you first bring the channel up. Once you are sure that the channel is basically OK, remove the resistor for further testing
 
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