Warning for those that run Rangers with an internal amp.

I'm pretty sure I burned up the amp in my N4 by hooking up a battery charger to my truck while I was off. I didn't realize the amp section stays powered up anytime the radio is plugged into power.

Anyhow, I got in my truck while the battery charger was hooked up and noticed that my inverter was beeping with an over voltage error and showed 17 volts on the display. The next thing I noticed was that the fan was running on the amp on my radio and the radio was off.

I hooked up a watt meter to the radio just to have a look and now the dead key is a maximum of about 30 watts on AM, even with the power turned all the way up.

I open it up, and it appears I killed three of the four transistors. The one good one heats up really fast to over 200 degrees as soon as you key the mic and the other three hover just above ambient temperature.

So this brings me to my question… Can I just put a matched set of transistors in it and it will be good to go, or does something need to be adjusted after replacing the transistors?

I don't see anything physically burned in the amp. All of the resistors and caps look ok.

 

It's an automatic charger and apparently it pulses the voltage really high at first to blast any sulfate off the plates. It works, because after putting it on the charger, the starter spins over faster and my APU will cycle instead of running nearly constantly. The effect lasts for a couple of months.

It seems to me the radio drew 35 amps at full tilt when it was new. The only relay I can think of right off the top of my head, with big enough lugs and rating, would be like a Ford starter relay. But I don't think those are meant for continuous hold-in. Got a relay in mind?

 

Are you talking about one like this? Will the windings handle being powered up all the time?

 

4 gauge cable... not going to be using spade terminals on that.

 

It is a very long run going back to the batteries. The cables coming out of the amp are 6 gauge. Any relay is going to have to have lug terminals. Or at the very least, screw terminals.