did I blow my Amp

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haklesup
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did I blow my Amp

Post by haklesup » Mon Jan 15, 2018 3:26 pm

I was working with an Alpine 2 channel car amp and trying to bridge outputs to a dual voice coil subwoofer. 4 ohms x2
Initially I got some output putting each coil on Left and Right but that's not a proper hookup. next step I paralleled the VC to obtain 2 ohms impedance and placed it across (what I thought were) the outer two (Left - and R +) but maybe I did it wrong, could have bridged any two terminals for a short time. (nothing was on for more than a minute or two in any config).

In any case, I don't get any output now and nothing inside looks fried. I'm using a digital monobloc amp for the sub now and that works so the speaker is unharmed.

https://pdf.crutchfieldonline.com/Image ... RPF240.PDF

Found and added this to post
https://www.manualslib.com/manual/95472 ... e=8#manual

Mostly I'm just asking if anyone Knows that this is a known way to blow an amp.

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Externet
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Re: did I blow my Amp

Post by Externet » Mon Jan 15, 2018 6:04 pm

Hi. Did you connect it this way ? Being the speaker symbols actually coils of the same subwoofer ?

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You are a skilled non-beginner... Let's fix it. Power supply rails fine, right ?
Warm up the scope...
- Abolish the deciBel ! -

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haklesup
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Re: did I blow my Amp

Post by haklesup » Tue Jan 16, 2018 5:15 pm

I agree it is repairable, I need to take it out of the car and put together a bench setup with some signal sources first. I've had these sitting on a shelf for nearly a decade and now I am completely refurbishing my 93 Explorer and these fit well under the seats. (they were insurance replacements for 2 that were stolen). That was a fun project now basically So I need to take a closer look at the whole setup, since there seems to be no output at all, not scratchy or low. I can use a scope but probably start with AC RMS measurements.done.

I studied the schematic some more, I don't think one can blow the output with an incorrect bridged hookup, I would have either one channel or ground on both sides or reverse phase because the negative speaker terminals are all common ground.



Can't see any of the ICs when I look inside, they must be on the hidden backside of the PCB and need some disassembly. The service manual does not show that side of the PCB either. its a mystery until I tear it down but not until after basic diagnostics.

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CeaSaR
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Re: did I blow my Amp

Post by CeaSaR » Tue Jan 16, 2018 5:31 pm

Hate to be the one to say this, but, most of those amps have a fuse. Is it good?

Addendum
I see the main fuse up by the transformer. I'm sure you checked it, but gotta rule it out.
Hey, what do I know?

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CeaSaR
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Re: did I blow my Amp

Post by CeaSaR » Tue Jan 16, 2018 9:11 pm

Next question.

You don't have the MUTE activated somehow, do you?
Hey, what do I know?

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haklesup
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Re: did I blow my Amp

Post by haklesup » Wed Jan 17, 2018 8:53 pm

Not the fuse. Initially I didn't check because the pilot lamp was turning on and off with the remote switch as expected but than I worried there might be a current path to the LED without power but although there is, the resistance is too high to light the lamp. I checked it today and was good. Mute and remote are basically the same thing external to the amp.

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dacflyer
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Re: did I blow my Amp

Post by dacflyer » Thu Jan 18, 2018 7:09 am

your outputs are the 4 big mosfets on the left, on the right is your power mosfets and diodes for the power supply.
is there not a PROTECT led lit up ?

here is how you properly bridge a car amp.. left and right input as normal.. then follow this...

https://www.wikihow.com/Bridge-an-Amplifier

what is the model and name of the amp you have ?

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