Question about Alpine MRD-M301 Car Audio Amplifier

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Negative speaker output touched chasis of amp.

Now amp is always in protect mode, reading CURR on display. With or withourt RCAs connected. I do not smell any burnt components. I also cannot visually notice any burnt or defective parts inside amp. What could this be, and how can I fix it MYSELF. I am pretty good with a soldering iron!

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Re: Negative speaker output touched chasis of amp.

If it reads current, that means protect mode. Unhook all wiring for a few minutes then connect them. it should start working. If the polarity is wrong, it overheats, or impedance is too low (under 2 ohms); the amp will display CURR until the problem is fixed. I'm sure it's not blown.Good luck.....Log in to crutchfields site and type 500mrdm301 in the search box/ that will give you the amp and you can download the pdf for the owners manual.

Posted on Jan 25, 2009

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Re: Negative speaker output touched chasis of amp.

Check all fuses on the unit, pull them all.
look for a way of resetting the amp.


that way you wont short a screw driver across the terminals on to the chasis.

Posted on Dec 15, 2007

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Installed lanzar 266 amp yesterday it went in protect mode on a song and now everytime i turn it on it is in protect mode

most commonly that means that somewhere there was an arc in the electrical either the pos or neg going into the amp or rcas or its the speaker wire from the amp to to the sub itself look especially for little wires touching opposit polarity wire (like a little +wire has moved and touched a - wire)

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Amp went to protect mode and will not reset to green.

Be sure the rca's are not getting severly pinched or worse you drilled a screw into them.

Second make sure your connecting the RCA's to the
1. OUTPUT of the radio
2. INPUT of the amp

if you connect any other way its wrong and could damage both radio and amp especially you screw into the RCA's your sending 12 AC Volts to ground.

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Let our Experts solve your "My amp lights up like normal then protection light red comes on and turns the amp off resets and tries again. What would be my course of action

disconnect all wires (including RCAs)
reconnect positive, ground, and remote.
Turn amplifier (car) on.
If it goes into protect mode again - there is an internal fault that requires professional repair.
If the amplifier idles as normal - turn off the car. Plug in RCAs & re-try
Failure? - replace RCAs as they may be pinched or faulty.

Lastly if all connections are made and amplifier idles without going into protection - you need to concentrate on your load (subwoofers).
Be sure they are wired properly into a resistance that amplifier is rated.
The lowest impedence that amplifier is rated is 2ohm.
That is possible with (2) 4 ohm subwoofers wired in parallel....
(4) 8 ohm subwoofers wires in parallel...
(1) Quad 1 ohm subwoofer...
or (1) Dual 4 ohm voicecoil subwoofer.

Any other combination will result in an impedence too low for your amplifier.

Using an OhmMeter (Digital multimeter set to Ohms 20) test each voicecoil against its advertised resistance. It should be CLOSE +/- .5 Ohms.

Any other reading means the voicecoil is blown.

Thanks for using FixYa - a FixYa rating is appreciated for answering your FREE question.

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My alpine amp displays CURR and nothing coms out!This happened after i was screwing the speaker wire in and I touched the amps chasis and it made a spark. I opened it up I did not see anything wrong with...

According to an Alpine owner's manual, for that type of amp, you should be able to remove power from the amp, then reconnect power to reset the error. If it doesn't reset, either there is another short in the wiring or the amp has permanent damage and needs repair.

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2 Answers

Amp displays the letters curr

have you disconnected all inputs and outputs on amp and retried starting it power only? if so your amp has an internal solder bridge and must be repaired by authorized repair center. Repair it or replace it at wholesale price from

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3 Answers

Only one sub works

The amp should produce no output when using the left negative and the right positive.

If the amp works bridged (left positive and right negative) with one speaker AND works when you connect one speaker from the left positive to the right positive, it would appear as though the right channel isn't getting any signal.

Try inserting only the left signal cable (nothing plugged into the right RCA jack) to see if the right channel will work when a speaker is connected to the right channel speaker terminals.

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Hi i am matt

If the protection LED lights only after the remote voltage is applied (head unit is switched on), the amplifier likely has shorted output transistors. If the protection LED remains lit without remote voltage applied, the amp may have other problems.

Does the protection LED light with no speaker wires connected to the amp and no RCAs plugged into the amp?

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When the protect mode is activated,always be the audio amplifiers IC's damaged you gotta change them.

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You say the protection mode only occurs when you plug the RCA's in. Does it have to be both RCAs or just one?

The other end of the RCA cable is plugged into the HU?

It possible the RCAs have too much DC voltage on them, causing the amp to go into protection.

Is there a short in the RCA cable?

I would definitely check out the RCA connection at the back of the HU, as it sounds like there could be other issues there. Make sure the RCA connectors aren't touching any other metal (especially +12V).

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if you are using RCAs as inputs to your amp.Swap the R to L @ RCAs to see if its comming in okay from radio.If both RCAs have audio then amp is bad ,If amp has any type of switches , move swithces to see if it comes back .Also if both RCAs inputs have audio .Move the RCAs when connected on amp to see if amp has bad connection in board to RCA jacks..If audio comes back on bad side when jack is moves .Then you have bad solder joints on board..If not then you must have bad outputs on amp..

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