NX-800 power button not working

[mikelimayankee]

Good evening, I just purchased a couple of NX-800 units for use with my offroad club. They came from a school bus fleet. I am trying to figure out why the power buttons don't work.

The radios all come on the moment 12v is applied to the main power leads, with no power to the ignition sense lead. The power switch does not turn the radios off or on. The radios came with Ignition Sense turned off. When I configure Ignition Sense to "Ignition and Switch", ignition sensing works as expected but the power switch still doesn't do anything. "Power Switch Status Memory" also does nothing in either setting.

I opened up the faceplate and was not able to detect any physical changes to the power switch on the faceplate. In all other ways, the radio works as expected. All three radios I purchased share this behavior, which leads me to believe it was an intentional modification in that fleet. I am curious if anyone has any ideas of how to undo that change so the power button works normally? Thank you!

 

[Dreamr]

I had this exact issue with an NX800 recently. There is a 1k ohm chip resistor on the power button line right next to the ribbon cable jack on the main board. If that resistor is bad or missing, the button won't work. On mine, the resistor was completely missing. That line normally has 3.2VDC on it. Pressing the button shorts it to ground, which tells the CPU to turn the radio on or off.

Your problem could also be the ribbon cable. But I've not yet seen one of those go bad.

 

[ak7an]

You might check the programming for the power setting. It can be set so the power button is turned off. Most likely the cause.

 

[FKimble]

Since they all do the same thing, it is probably programed that way.

Frank

 

[tlemke940]

i dont think the nx-800s have a way to program the power switch to not work i do think you may be on the right track with the resistor tho i have seen that i have also seen the key pad to just be bad and well you have the face off use another key on the key pad to try and use the pwr button if that works then it is just a bad key pad. i have seen just the pwr button go bad with people who only use that button all the time like bus drivers who only use one channel.

 

[phillmobile]

radio set to ignition feed?

 

[mikelimayankee]

I had this exact issue with an NX800 recently. There is a 1k ohm chip resistor on the power button line right next to the ribbon cable jack on the main board. If that resistor is bad or missing, the button won't work. On mine, the resistor was completely missing. That line normally has 3.2VDC on it. Pressing the button shorts it to ground, which tells the CPU to turn the radio on or off.

Your problem could also be the ribbon cable. But I've not yet seen one of those go bad.

This was it! The resistor is R630, depicted on page 73 of the service manual. Thank you!