Intermittent Sound From Amp?

[Peter]

Hi Everyone!

Car: MQ Patrol – the bush basher / daily driver!

Deck: Pioneer, with front pre-out and rear/sub pre-out.

Amp: Sony XM-460GTX, front channels to splits, rear channel bridged for sub.

Speakers: Splits and sub.

Problem:

Installed this about 12 months ago – working fine. Then the sub started to quieten, adjusted deck and amp, all good for a while, then one day the sub cut out completely. Checked wiring etc. all good. Played around with RCAs, when I unplugged one rear channel RCA, sub got loud, as I was plugging it back in front speakers crackled and sub cut in and out. I left only one rear channel RCA plugged in as a quick fix – all good. Sub died again. Completely unplugged rear (sub) RCAs – sub loud again. Left as is. Driving along one day – normal road, sound cuts out. Next morning back on, then when driving to work, crackles and cuts out – all speakers (sub and splits). Think it is possibly the deck, take home CD player with RCAs outside, power-up and plug into amp through RCAs – no sound on any channel – can’t be deck – must be amp. Play around with RCAs – no good, no sound at all – all fuses good, power and protection light still green. Take amp into A1 Audio (Perth), who test on bench for a week in different modes – no issue. Take hone last night and put back into car, working fine, and then sub cuts out again. Unplug one rear RCA and sub back and loud again, unplug both rear RCAs and sub as loud as it should be, front speakers working, but no sub control through deck as no rear RCAs plugged in.

Sorry for the long description, but does anyone have an idea what the problem would be? The guy at A1 said the RCA inputs on the amps sometimes pack up, but when they tested everything it was fine?

Any help would be much appreciated, as I just want to have the amp running normally, and be able to control the sub from the deck as it should be.

Thanks!

Peter

[Carbon 34]

have you run another RCA OUTSIDE the car to the amp or swapped the front and rear RCA around for testing ? you could have a bad solder joint on the RCA wires or pinched wires under a seat or bolt

your sure they checked to make sure the amps RCA jacks aren't broken off the curcuit board, very common lately on made in china gear. without solid support, and in a truck break even faster from vibrations. easy to fix if so.

give your wires a wiggle test while on low volume , starting with the amp area, then under the dash. ???

if the deck/truck was offroaded severely then maybe, depending on if it has rotary controls or push button ? what model pioneer radio? removable face ???

Edited February 8, 2011 by sapphiregraphics

[Peter]

Thanks for the reply!

- When the amp stopped producing sound completely, I took my stand alone CD player from my system in the house, ran an extension cord out to the car, and plugged the RCA jack of that into the fron and back channels, adjusted the gains and still no sound? So I thought definately not the RCAs outputs from the deck.

I'll switch the RCAs around from the deck again today, and see what happens. I took apart the amp and it seems that the RCAs aren't broken - and A1 Audio checked this, and like I said when they tested it on the bench everything was fine!? But as soon as it goes into my car the rear sub channel starts playing up, and the front speakers crackle and cut in and out as I move the rear (sub) RCAs on and off the terminals?

I'll try the wire wiggle as well...

The car is not off-roaded that severely, I always take it easy - the deck is detachable face, with the buttons all flush, and a little rotary controller in the middle - I can get you the model if it makes that much of a difference?

Any other suggestions?

Thanks!

Peter

have you run another RCA OUTSIDE the car to the amp or swapped the front and rear RCA around for testing ? you could have a bad solder joint on the RCA wires or pinched wires under a seat or bolt

your sure they checked to make sure the amps RCA jacks aren't broken off the curcuit board, very common lately on made in china gear. without solid support, and in a truck break even faster from vibrations. easy to fix if so.

give your wires a wiggle test while on low volume , starting with the amp area, then under the dash. ???

if the deck/truck was offroaded severely then maybe, depending on if it has rotary controls or push button ? what model pioneer radio? removable face ???

[BundyBear]

Troy

another possibility (it's a bit out there),

could the voice coil be rubbing on the housing (Distorted basket from the bushbash'n), creating a partial short ( reduced volume) and overloading the amp (total sound loss)

Peter

Try bushing the sub cone in gently (spreat ya finger tips around the centre of the sub) does it float gently, or can you feel a scratchy sensastion

[Carbon 34]

yeah could be a dragging slightly burnt voice coil , or a tensil lead from the voice coil to the solder joint on the speaker frame shorting out on the speaker frame when it moves just right or plug inside the speaker box

is loose ???.

a few of the older sony stuff had bad capacitors on the pre amp side of the board, but most of the time they would go into protection or squeal loud internally to the amp itself.

sorry I missed the testing of the deck already, rotary dials and detachable face decks get dirt in the connections and do weird things. drop out etc. dirt roads and car audio dont mix well...lol

use marine equipment if you drive in the dust all day long.lol

[Stagea_Neo]

along the same vein as above/those in the know + my 2 cents.

if system as been in for a while, perhaps check over, trim ends of wires/terminals and re-terminate terminals to speakers/amplifier.

make sure all nice tight/good contacts. Hopefully no loose terminals on the amp to circuit board or speaker basket to cone themselves.

whilst everything good on a new install, good to check over every 2yrs with vibrations/knocks/pot holes etc..

(which re-mind's me, getting a bit of hum, gotta check the earth on rear amp)

[SPINR31]

i could troll and say sony is POS but i wont.

instead i recommend atleast getting good wire and rca's (i use rockford fosgate gear). that should fix your problem, if not the problem could be ground related