Problems With Car Amp

marshallf3

Joined Jul 26, 2010
2,358
Considering they sell PC power supplies for $10 around the US, unless you spring the $ for a good one you really can't expect much out of them. Ratings are often only peak and that's with even loads across the board. One with a good solid single 12V rail will cost you but they do not last forever as they weren't designed to. Things are changing as the motherboards and graphic cards increasingly depend on the 12V rail but unless you're ready to spend some $ don't rely on one as any sort of a power source as you're wanting it to supply.

Is it that hard to find an old (but still acceptable) car battery over there?

I would NOT consider a bare battery charger as there's rarely if ever any filtering or regulation in them unless hooked up to a battery.
 
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Thread Starter

Shagon

Joined Aug 19, 2009
48
There is a direct short between the 3.3v Rail and the Ground could it be possible that this short is causing an overload protection that limits the current running through the entire system?
 

tom66

Joined May 9, 2009
2,595
There is a direct short between the 3.3v Rail and the Ground could it be possible that this short is causing an overload protection that limits the current running through the entire system?
Are you sure? How did you measure it? Is there any 3.3V output at all?
 

R!f@@

Joined Apr 2, 2009
9,918
It is not a direct short. There is low resistance resistor at each output. A short will shut down the power supply. Period.
 

Thread Starter

Shagon

Joined Aug 19, 2009
48
Are you sure? How did you measure it? Is there any 3.3V output at all?
Using a multimeter I tested for continuity it gives a continuous beep when there is a closed path no beep when its open.

I got a continuous beep across the +3.3v rail (orange wires) and the ground (black wires)

Oh and yes there is 3.3V
 
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Thread Starter

Shagon

Joined Aug 19, 2009
48
It is not a direct short. There is low resistance resistor at each output. A short will shut down the power supply. Period.
I also tested it on the working power supply powering this computer. I got one single beep which is caused from the cap across the 3.3v rail and Ground.

when you test for continuity across an electrolytic cap it gives a single beep.

But on the power supply with the issue I got a continuous beep. It has to be a short doesn't it?
 

Kermit2

Joined Feb 5, 2010
4,162
It is if the resistance is less than 1 Ohm.

Those 'beep' settings on meters will beep when a resistance lower than 1000, or sometimes as low as 200 Ohms is found.

It will beep when it's just a low value resistor.


WHAT DOES THE METER READ?
 

Thread Starter

Shagon

Joined Aug 19, 2009
48
It is if the resistance is less than 1 Ohm.

Those 'beep' settings on meters will beep when a resistance lower than 1000, or sometimes as low as 200 Ohms is found.

It will beep when it's just a low value resistor.


WHAT DOES THE METER READ?
Ok so what about the 12v rail and the 5v rail don't they have the same output resistor? cause when I test them I get one beep but with the 3.3v I get a continuous beep.
 

Thread Starter

Shagon

Joined Aug 19, 2009
48
If you can measure 3.3V then there is no short.
Hmm I think I see your point you are saying that if there is a short that the 3.3v would send 3.3V on the ground wire and if I measure for voltage across the 3.3V and the Ground wire they would cancel each other out?

But remember that the ground wire is grounded 0v so shouldn't that explain wire the ground wire would not read 3.3V?

I hope that my questions aren't a bother... I am a beginner at this. But I wish to learn.
 

Thread Starter

Shagon

Joined Aug 19, 2009
48
Ok guys... Low resistance of about 50 ohms while the 12v rail are high with about about 200K ohm so this explains the beep...
 

R!f@@

Joined Apr 2, 2009
9,918
You are way confused


If voltage is there then there won't be a short.
There will be low resistance path on each rail in a PC PSU
 

Thread Starter

Shagon

Joined Aug 19, 2009
48
No your right there is not short circuit just a low resistor.... I tested for resistance between the 3.3v rail and ground I got about 40 ohm....
 

Thread Starter

Shagon

Joined Aug 19, 2009
48
Ok guys.... I found the culprit.... its a CAP... but its not in the power supply its in the amplifier itself... it leaked out.... tested it and got nothing... so I removed it and saw this massive hole underneath it...
 

tom66

Joined May 9, 2009
2,595
Ok guys.... I found the culprit.... its a CAP... but its not in the power supply its in the amplifier itself... it leaked out.... tested it and got nothing... so I removed it and saw this massive hole underneath it...
Well it's probably a combination of the two. It's possible the amplifier manufacturer cheaped out on the capacitor? What are the ratings and brand of the capacitor?
 

Thread Starter

Shagon

Joined Aug 19, 2009
48
Well it's probably a combination of the two. It's possible the amplifier manufacturer cheaped out on the capacitor? What are the ratings and brand of the capacitor?
its a 2200uF Capacitor 50v as for brand... I aint No...
 

tom66

Joined May 9, 2009
2,595
its a 2200uF Capacitor 50v as for brand... I aint No...
It might say something like Nichicon, Panasonic, Rubycon or Dublier on it if it's a decent brand.

It might say something else if it's a cheaper brand, can you take a pic? I'm just curious. A 50V cap is *very* high for a 12V line. If it is actually filtering the line then it is more than generously specified. Which is good to see in devices. However, it could be on the output of a boost converter for driving the speakers - I don't know.
 
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