Top 20 MTX Thunder 421D Car Audio Amplifier Questions & Answers

The LED should be red. If you are not getting power to the sub, make sure the speakers are connected properly to the amp. Also make sure that the gain control is turned up. If it is all the way down, you will not hear anything from the sub(s). If none of that works, it is possible that you have a blown sub. If you smell a burnt smell near the speaker magnet, there is damage to the voice coil in the sub.

http://www.retrevo.com/support/MTX-421D-Car-Amplifiers-manual/id/18680ci265/t/2/
Please go to this above link, and download what you need.

that first number most likely is 2N414A. Goto NTE cross refference web site and put this number in, it will show you a cross for it with a picture of the transistor to match it to the one you have. Hope this helps good luck.

Check your wiring and see that your power wire is not in contact with any part of the body of the car. I also recommend soldering the ends of all wires, to prevent them from splitting especially on the amp terminals.

If you have proof of purchase(invoice or receipt) showing the purchase date and you are still within the warranty period then yes it would be repaired by MTX under the warranty guidlines, and by the way MTX is great at customer service and they are great to work with(very fair)!!!!
Keep in mind that the seal on the bottom of the amp cannot be broken or that will void warranty coverage.
Give them a call, you will be glad you did!
800 225 5689 - MTX Customer Service & Amplifier Service Center
Good luck !

the amp is under to much pressure get a bigger 1

Make sure that your connection at the battery is still good-sometimes the wire corrodes up front when your system is installed for a long time-so check that out and of course the fuse that you installed a foot away from the battery so that you dont burn your vehicle down if a short occurs somewhere down the line

Hello jaimemm_77,

The MTX 421d is a mono amp. It only has one output channel.

If you are asking about hooking up only one channel to the input, then no, the amp will not overheat. But the output will be significantly reduced. It would be best to use a "Y" adapter with a single female and two male connectors to split the channel into both inputs.

Hope this helps.

that means that you have a short in the power supply or in the output circuit.

yep no good not worth fixing have that same prob with a few of my customers replace it you better off

Connect the remote turn on to the blue wire w/white stripe coming from the head unit, NOT the solid blue wire which is the antenna turn on.

Im sorry to have to inform you my friend, if you saw smoke, you burned one or more of the resistors or output devices inside the amp. Without a service manual, it will be a hard call on what exactly cooked. In alot of cases please forgive me for saying so, but the ampis not worth taking into a repair shop to be repaired, because of the high cost these days of labor. Its too bad there are no user replacable parts inside of these amps. Good Luck. Ps Please do not forget to rate this thread?

It is too old for online manuals. Any colour light would show it has power and usually a red, green or blue LED. Red is sometimes reserved as a fault condition in conjunction with another power light. https://www.google.com/search?q=mtx+810d+amplifier+manual https://www.google.com/search?q=mtx+810d+amplifier ..

See if the videos help https://www.google.com/search?q=mtx+terminator+tna251+RCA+sockets ..

MTX will know that one. https://www.google.com/search?q=make+my+MTX+TERMINATOR+AMP+1+OHM+STABLE ..

What amp r u using

yes a higher voltage rating is OK lower voltage rating is not good.

If you have to ask, take it to a repair shop.

THE GREEN LIGHT SHOULD SHOW WHEN AMP IS POWER UP AN RED WHEN IN PROTECTION MODE