Question about MTX Thunder TA7801 Car Audio Amplifier

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My amp doesn't turn on...

I think it's the power supply of my amp because it have 0 ohms in their terminals, do you know where i can find another one????

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Re: my amp doesn't turn on...

Hi i have the MTX thunder 7801 and it doesnt do anything
everything is connected as the manual says but i get a red light with service only

what can that be?

Posted on Apr 13, 2008

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Re: my amp doesn't turn on...

If there is a zero ohm connection across the B+ and ground terminals, it should blow the fuse as soon as you apply power.




Posted on Oct 10, 2007

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I have a kicker zr 120 and the left channel works but the right channel does not, i tore it apart and checked the rca connections with an oscilliscope and both have a good signal coming in, do you have a...

Check the transistors with an ohm-meter. When you find one that has 0 or close to it ohms between 2 or especially all 3 pins you've found the problem 95% of the time.
If one channel works it's not in the power supply. There will be 2 diods that look like transistors but are diodes that convert the ac voltage in the mosfet power supply to dc voltage that powers the output transistors. The 2 diods will have 0 or almost 0 ohms between the 2 outside leads, this is normal so don't confuse them with the transistors. A reading like this on a transistor would mean it's shorted, junk,
Output transistors normally have at least 200 ohms between any of the 3 leads. It's much more common for them to read 0 ohms when they go bad than for them to give in infinate resistance.
If you know how to check the input signal with a scope, this should be a piece ok cake. Removing the bad ones is usually the hardest part.

Good luck

Apr 15, 2010 | Car Amplifiers

1 Answer


The MRD-M300 has speaker-level inputs so you can easily use it with any car stereo. Hook it up and hear what good bass can sound like!
  • 150 watts RMS x 1 at 4 ohms
  • 300 watts RMS x 1 at 2 ohms
  • MOSFET power supply and output stage
  • STAR Topology for cleaner sound
  • Bass Engine® features:
    • low-pass digital crossover, 30-200 Hz, 24 dB/octave
    • variable subsonic filter (15-50 Hz in 5 Hz steps)
    • parametric EQ variable from 30-160 Hz
    • Bass Compensator enhances low-end definition
  • top-mounted digital control center with cover
  • time correction 0-10 milliseconds in 0.5ms steps
  • phase correction 0-180° selectable
  • digital readout
  • detachable front cover
  • blue power LED
  • delayed turn-on
  • requires 8-gauge power and ground leads — wiring and hardware not included with amplifier
  • speaker- and preamp-level inputs
  • gold-plated terminals
  • 8-5/16"W x 2-11/16"H x 11-1/2"D (10"D without front cover)
  • 1-year warranty

May 29, 2009 | Alpine MRD-M300 Car Audio Amplifier

2 Answers

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.

May 27, 2009 | Kicker (ZX750.1) Car Audio Amplifier

1 Answer

What are the correct spaekers for the gm 5100t ?

    CEA-2006 Compliant Amplifier Power Standard:
  • 125 Watts x 2 @ 4 ohms <= 1% THD+N
  • 380 Watts x 1 @ 4 ohms BRIDGE <=1% THD+N
  • 75 dBA Signal-to-Noise Ratio
  • Peak Music Power: 250W x 2 (4 ohm) / 760W x 1 (Bridge)
  • 2 Channels
  • Continuous Power @ 4 Ohm: 125W x 2
  • Continuous Power @ 2 Ohm: 190W x 2
  • Continuous Power Bridged @ 4 Ohm: 380W x 1
  • Frequency Response: 10Hz-50kHz
  • THD (1kHz, 4 Ohm): <0.015%
  • Signal to Noise Ratio: >95dB
  • Dimensions: 11 13/16” x 2 3/8” x 12 7/8”
  • PWM Regulated MOSFET Power Supply
  • Balanced Isolator Input Circuit
  • Oversized Screw-Type Power/Ground Terminals
  • 2 Channel RCA Inputs
  • Speaker Level Input
  • Screw-Type Speaker Terminals
  • Hi-Volt Input Level Control (200mV-6.5V)
  • Bass Boost (50Hz, 0/6/12dB)
  • Selectable LPF (80Hz, -12dB/Oct.)
  • Pioneer 1-Year Warranty
I'm assuming the subwoofers were bridged and couldn't handle the power. Make sure you have atleast 300 watts peak power wattage.

Feb 05, 2009 | Pioneer GM-5100T Car Audio Amplifier

2 Answers

Amp voltage

Well this is interesting, Let me start by saying if you have a 2 ohm load and your system is set for 4 ohms you are going to overdrive your load and burn up your amplifier, maybe not right away, but sooner or later it will fail due to electrical and thermal stress bought on by power dissipation issues.

Yes you can get 2000 watts out of your amps, but the correct way is to bridge your amplifiers if you can, and terminate them into the proper load.

Thank you,


Apr 21, 2008 | Jl Audio 1000/1 Car Audio Amplifier

3 Answers

How should I wire my 3 subs to the 500/1 amp???????

First of all how many ohm's are each subwoofer rated at . Are the subwoofers dual voice coil or single voice coil. Once I know that I can help you. I think the JL amp is not recommended below a 2ohm load.

Mar 16, 2008 | Jl Audio 500/1 Car Audio Amplifier

1 Answer

Amp a2801q

Audiobahn A2801Q
Product Description:
Class A/B MOSFET Circuitry
200 watts x 2 @ 4 ohms stereo
280 watts x 2 @ 2 ohms stereo
560 watts x 1 @ 4 ohms mono

Volt Meter With Blue Illumination
PWM MOSFET Power Supply
Double Sided Glass Epoxy Circuit Board
THD: 0.02%
S/N Ratio: >100dB
Frequency Response: 10Hz - 40KHz (+/- 1dB)
Variable 18dB Hi-pass Crossover: 90Hz - 750Hz
Variable 18dB Low-pass Crossover: 30Hz To 120Hz
Bass boost @ 45Hz: 0/18dB
Subsonic Filter: 20Hz to 50Hz
RCA Throughput Connections
3-way Protection Circuitry: Thermal, Short Circuit and Overload
Cooling Fan
Cobalt Blue Illumination
High gloss Chrome Plated Finish
Nickel Plated Block Terminals
Dimensions: 2"(H) x 12.75"(W) x 15.5(D)
1-year warranty

Jan 02, 2008 | AudioBahn A2801Q Car Audio Amplifier

2 Answers

PB1500 no diag. lights - Power - OK

I don't know how you checked the fuses but if you didn't use an ohm meter, you need to confirm that you have B+ and remote at the amplifier.

With your multimeter set to DC volts, the black meter lead on the ground terminal of the amp and the head unit on (so the amp will have remote voltage applied), touch the red lead alternately to the B+ and remote terminals of the amp. If the voltage is below ~11 volts, you need to check the wiring feeding whichever line is too low.

If the voltage is sufficient at the remote and B+ terminals, the switching power supply has probably failed in the amplifier.

Dec 20, 2007 | Pyramid PB1500 Car Audio Amplifier

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