Teardrops n Tiny Travel Trailers

I pulled this power converter out of a little scrapped out motor home thinking I could use it in my Teardrop. I connected it all up the way I show it here, but when I plug into 120 with the converter, it shuts off my stereo. Anyone here have any ideas why it would do this? I checked voltages and it all seems OK. I am pulling my 12v power from the blue wire which is what I thought was right.
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12v Red / Battery +
12v White / Battery ground
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120 AC White / Transformer Neutral
AC Black / Transformer Hot

TLI too little information, What voltage readings are you getting? What is the brand and model number of the converter?

OK, I figured it out. The blue wire is unfiltered and any modern stereo will reject the dirty signal. I read 30v AC on the DC scale. So I am using the red DC wire and it works perfectly. Charges 14.8 for a few minutes and drops down to13.1v. No noise on the stereo. Thanks all.