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power problems 

 

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 Post subject: power problems
Posted: Fri Jul 11, 2008 12:34 am 
Oompa Loompa
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Ride: el falcon

Location: canberra
ACT, Australia

hi all ive recently put 2 amps in my el falcon 1 for the four speakers one for the sub and now every time i go for a drive the amp for the sub seems to cut out at a certain level at random times and the problems at its worst at night time with the lights are on, the volume wont even go to half way without cutting out. its only the amp for the sub thats doing it and the other just keeps going strong. its really bugging me.

im guessing a power issue of some kind just wanting to get some suggestions

thnx
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Posted: Fri Jul 11, 2008 12:41 pm 
Getting Side Ways
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Is the amp loosing power or is it entering safe mode?

What size cable are you running to the amp?
Have you updated the ground wire at both ends?

It's usually a bad earth, most people do a half assed job at it.
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Posted: Fri Jul 11, 2008 1:00 pm 
Oompa Loompa
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Location: canberra
ACT, Australia

well its not entering safe mode the amp is fine and the sub just skips a few beats. this may sound odd but it seems when im driving if im accelerating its fine if im just idleing it cuts out. but i am running 4 gauge cable from the battery to a ditribution block then it splits into to 8 guage cables then straight to the amps. and what do you mean ground wire at both ends ive made a new one for the two amps.
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Posted: Fri Jul 11, 2008 3:12 pm 
Getting Side Ways
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by the sound of it you have a voltage issue and if rev related, there is a good chance that your alternator is on the way out.

Try a cap (but they generally only help with suddun voltage drop due to extreme load on the amp)......

Do you notice any other symptoms, like duller headlights at idle or dimming dash lights etc?

You could also try putting a fatter earth strap between the battery and the chassis/engine. Sometimes, the factory strap won't cope with large audio applications.

It sounds as tho you shouldn't have too many issues with the amp cabling with 4 gauge into 8 gauge........

 

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Posted: Fri Jul 11, 2008 9:24 pm 
Oompa Loompa
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Ride: el falcon

Location: canberra
ACT, Australia

headlights are fine, there is no noticble diffrence apart from blinking with the big bass parts of a song not much but its enough to notice and same with the dash lights

ps: where can i pick up earth straps are they a basic generic part or are they made for the model of car
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Posted: Sun Jul 13, 2008 2:46 pm 
Parts Gopher
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VIC, Australia

hey man can make your self a nice beefy eart strap with a some easy to find materials.
I've got 2 x 15' about to go in my car running of a soundstream mono block and have had 2 LX7 kicker 15's and have gone through like 5-6 alternators now!! dont be surprised if it just aint up to it.
with the blinking is it dash lights and or the deck ?
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Posted: Sun Jul 13, 2008 5:29 pm 
Oompa Loompa
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Location: canberra
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ive got some powercable laying around from when i put it all in its 8 guage could i use that and what are the signs that the alternator is bad cause now both amps cut in an out its gettin worse
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Posted: Sun Jul 13, 2008 7:43 pm 
Stock as a Rock
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This sounds like a voltage drop issue. Check with a voltmeter at the amp.
Any bad joins or bad wire along the cable path from the battery to the amp or the amp to the earth will cause some resistance.
Any resistance along the path will cause a voltage drop by the formula: Vdrop = I(current) x R(resistance).

Now, normally there's a really small resistance, but some bad wiring could create an unacceptable resistance and in a car it doesn't take much because we've only got 14Volts or so to work with.

Normal running creates a small current draw and so a really small volt drop, but when there's a bass note it draws a large spike of current through the wire which creates a large volt drop.
So when the current jumps up, the remaining voltage at the amp is not enough to power your amp properly - so it cuts out.

Example 1. Normal running system
Voltage at battery = 13.5V
Bad joint resistance = 0.1 Ohms
Current at low volume = 2 Amps
Voltage drop at resistance point = 0.1 x 2 = 0.2V
Remaining voltage at amp = 13.5 - 0.2 = 13.3V <Totally ok

Example 2. Same system with the volume cranked up
Voltage at battery = 13.5V
Bad joint resistance = 0.1 Ohms
Current at high volume = 50 Amps
Voltage drop at resistance point = 0.1 x 50 = 5V
Remaining voltage at amp = 13.5 - 5 = 8.5V <Not enough to run an amp

 

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Posted: Sun Jul 13, 2008 10:04 pm 
Oompa Loompa
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Ride: el falcon

Location: canberra
ACT, Australia

thanks for all the suggestions folks im on school hols so i got plenty of time to go right over the system. and i think i have an idea were there could be a possible bad join so ill check that tmw along with upgrading the earth from battery to car even if its not the problem my system will only get bigger so i may aswell do it now. ill let u all know how it goes
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Posted: Sun Jul 13, 2008 10:28 pm 
Parts Gopher
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maximus wrote:
This sounds like a voltage drop issue. Check with a voltmeter at the amp.
Any bad joins or bad wire along the cable path from the battery to the amp or the amp to the earth will cause some resistance.
Any resistance along the path will cause a voltage drop by the formula: Vdrop = I(current) x R(resistance).

Now, normally there's a really small resistance, but some bad wiring could create an unacceptable resistance and in a car it doesn't take much because we've only got 14Volts or so to work with.

Normal running creates a small current draw and so a really small volt drop, but when there's a bass note it draws a large spike of current through the wire which creates a large volt drop.
So when the current jumps up, the remaining voltage at the amp is not enough to power your amp properly - so it cuts out.

Example 1. Normal running system
Voltage at battery = 13.5V
Bad joint resistance = 0.1 Ohms
Current at low volume = 2 Amps
Voltage drop at resistance point = 0.1 x 2 = 0.2V
Remaining voltage at amp = 13.5 - 0.2 = 13.3V <Totally ok

Example 2. Same system with the volume cranked up
Voltage at battery = 13.5V
Bad joint resistance = 0.1 Ohms
Current at high volume = 50 Amps
Voltage drop at resistance point = 0.1 x 50 = 5V
Remaining voltage at amp = 13.5 - 5 = 8.5V <Not enough to run an amp




ey man good info in there. Good luck with yor stereo man
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Posted: Tue Jul 15, 2008 1:37 pm 
Oompa Loompa
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Age: 27

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Ride: el falcon

Location: canberra
ACT, Australia

so i think im up for another alternator. :( i put another battery in it and checked all connections in the system and yeah no good so how much would i be looking at for a new alt or even a reco one
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