I have a phoenix gold XS4600 4ch amp that 3 of the four channels work perfectly. On the right rear channel randomly it stops playing music and starts popping loudly like its sending DC/Rail voltage to the speaker. There isn't much pattern to when it starts and how often it repeats and i've done some poking with my DMM but I don't know what else to check. I've also acquired a 40mhz oscilloscope and poked around and found when the amp does start popping its sending +30v to the right rear NEGATIVE terminal; positive terminal seems fine with the DMM and scope. The channel will still play music while its popping but the popping is so intense it blew a speaker the previous owner of the amp had. While its popping the other channels keep on playing.
Also the same signal ( random +30v) comes in and out of one of the big fets for the right rear channel so maybe its a smaller transistor that triggers the bigger fets thats dying? Or due to the repetition repeating maybe a cap is bad?
I took the main board out of the amp to get to the bottom of the pcb but now my prob is that I cannot repeat the issue as the fets that are now floating without a heat sync get too hot before the amp starts glitching.
I'm powering the amp off of a 5amp bench power supply so as not to overload anything to the point of smokey failure but I did note that amperage draw jumps significantly when it's "popping" I unhook the speaker and popping stops obviously and amp draw stabilizes. This amp does seem to have excessive idle amperage draw; about 2.5A compared to about .5-1A for my memphis 1500w monoblock class d and similar for a junky power acoustik gothic "1200w" amp i have to reference (though some of that I attribute to the PG amp being older and better built). Also the amperage draw slowly ramps from power-up either hot or cold. it starts out normal and slowly builds up to peak idle draw of 2.5A with or without load (speakers) or any music playing.
One thing to note this amp used the little DIP/IC resistor network to control crossover points and the one for the rear channels had 2 damaged and missing pins. The only way that amp will play out of the right rear is if the "crossover defeat" button was pressed; and pressing that button while the amp is powered will reward you with a very powerful THUD out of the right rear channel. I plan on using an outboard crossover but I have fixed the pins on that resistor IC and the thud is gone and crossover works as normal.
Also that channel has an excessive amount of 60HZ hum compared to the other channels (RCA's and speakers swapped around and moved around physically to rule out 120v ac cord interference or a bad speaker). I don't know if that's relevant but I thought i'd mention it. Its not bad but it is noticeable in a quiet room and does not seem to change with gain or input volume. Touching the case of the amp will make it increase out of that channel slightly but not the other channel.
My guess is repeated pressings of that button or that IC not being right caused something in the right rear channel to overload partially fry'ing a FET or maybe a cap?
Anyway any input on what else I should check or replace?
After reading many threads on this forum last night I may go ahead and order some new caps for this amp as I plan on using it for the highs in my car. Right now I have a Pioneer AVIC-N3 feeding a memphis 1500w class d amp that will be powering 3 alpine type r 12s in a ported box tuned to around 34hz and am looking for some good 6.5 and 6x9 speakers for mids/highs. I have stock speakers now powered off the head unit and SQ and SPL is non-existent lol. I have a set of JVC 6.5" coaxials I got that I may run but i'm really hoping to score a set of good used components for the front and some matching 6x9's in the rear.
Anyway for S&G here is a pic from the other night after I got my scope when I was testing this amp.
Once removed you can use a 9v battery and a DMM to test to see if the transistor works or not.
I had to remove ALL of mine because I didn't know which one(s) were bad. Good times.
but you can keep trying if you want to