Mac Audio Fearless 1000

[kinser]

Hey guy, bought the above amp BNIB about 4 months ago, worked perfect up till now.
setup was:
iPod---------->Mac Audio--------->2Ch Amp

TC-2000 Sub JBL Components

had no head unit.
one day i was driving and the 2ch amp was smoked, saw that the RCA wires between the two amps were melted and burnt, though the Mac audio still worked and the JBL were fine.
Then i got a Panasonic CQC-8401 HU from a friend, hooked the JBL's up to its internal amp, and the Mac Audio Via RCA sub output. got no sound from the sub, just lots of humming and what sounded like feedback with distortion(?). so i hooked up my iPod to make sure the Mac Audio wasn't stuffed.. worked for a few seconds.. next thing i see the RCA wire (connecting the iPod to the amp) is on fire&melting, so i quickly disconnected my iPod and cut off power from the battery.

i suspect that its go something to do with the input section, since my sub is alrigh, and it never went into protect mode..

Can anyone help me out?

Thanks,
David

[Perry Babin]

With the Mac Audio amplifier connected to B+ and ground (no RCAs plugged into it and no speaker wires connected to the amplifier's speaker terminals), measure the DC voltage from RCA input shield (red probe) to chassis ground (black probe).

Do the same with the amp on.

What is the DC voltage for both?

If it's less than 1v, measure the resistance from the speaker wires to chassis ground. You should read infinite resistance from the speaker wires to ground.

[kinser]

haven't had a chance to test yet (also lost my multimeter), but i opened it up now, and nothing looks or smells burnt, not components, nor the tracks on the PCB. all seems good in the Mac Audio amp.
then i opened up the 2ch amp, expecting to see a burnt chip amp and PCB, i was very surprised to fine that its all intact.... very strange.

could you have any idea as to what could cause the signal wires to catch on fire and burn? in both cases my PSP was hooked up as the source of signal, it was not harmed either..

Thanks,
David

[Perry Babin]

Shorted power transformers are the most common fault that causes 12v to be applied to the RCA shield. The PSP was likely connected to some sort of 12v power supply/charger that was connected to the chassis ground.

[kinser]

running off batt' lol. but.. the RCA cable was a quick made setup to test the sub and i did not insulate the ground and signal wires, might have touched something that caused a short. but what i still cant understand is what caused it the first time...
ill give it a bech test here today, to see if both amps run alright.. might just be bad grounding in my car, no?

Thanks,
David

[Perry Babin]

Power up the amps and measure the DC voltage on the RCA shields of the amp (black meter probe on the chassis ground terminal, red probe on the RCA shields). It should be very near 0v. Try it with and without remote voltage applied.

MTX amps are the only ones I know that would try to ground through the RCA cables if there was a bad ground. Rockford amps would do it but only if they were damaged (diode shorted in the amp due to 12v contacting RCAs).