I am getting to the point I am firing up the HDX alongside the audio and RF systems on my panel. It is mostly working but I am getting the dreaded audio coupling from the display PWM. I know it is the display backlight because the intensity of the hum comes and goes with the display backlight. For example, during the boot cycle, the hum starts full volume, then fade and comes back as the HDX logo brightens, goes away on black screen, then once the system diagnostic screen comes on, it is steady. I can influence the intensity by adjusting the brightness, too. The hum is about 120Hz (about double the common 60Hz hum).
Thinking I have an inadequate grounding, I tried jumping the HDX case to radio frame GND. That did not materially change the intensity or the quality of the hum.
Any suggestion on where I should look next? When I turn the HDX off, the hum goes away completely.
Hiroo
Thinking I have an inadequate grounding, I tried jumping the HDX case to radio frame GND. That did not materially change the intensity or the quality of the hum.
Any suggestion on where I should look next? When I turn the HDX off, the hum goes away completely.
Hiroo
