Hello, I have replaced the 12v power supply in my old boombox with a Dell laptop power supply rated at 15VDC @5A. I did this because I had added an EQ/power bootster and needed more power for it (I have also added 2 D batteries for a total of 10-D or 15V of battery power! This boombox really rocks!!!).
I assumed that the Dell switching power supply was adequately filtered, but discovered after I installed it that it interferes with the FM radio reception. It doesn't cause noise in the radio audio, but serverely diminishes radio reception; I can only get in the strongest stations, and even they flicker in and out of stereo. When I pull the power cord out to run it on battery power, the radio works fine. Moving the power supply closer and farther from the radio section doesn't make any difference, so I assume that the problem is with HF noise on the 15V line? What would be the best and cheapest way to fix this?