(Car Audio) Alpine MRD-M1000 amp no errors, but no sound

[torpex505]

I just found that my Alpine MRD-M1000 amp is not putting out any sound.(I never use the car that it is in, so I have no idea when it went out) It is a Single-Channel (Sub) amp. When the amp is connected and on, I don't receive any error lights, there is just no sound coming out. I thought it may be faulty RCAs or speaker wire, but I swapped a different amp in it's place and everything works as it should. I opened the back panel, and everything looks to be ok. Any advice on what I should start checking?

Thanks

[cadiman]

I had a couple of alpine amps but I never had to work on them. Car amps have a switching power supply driven by a modulation chip. This is half of any car amp.
If you can verify the power supply is working you can move on to the audio end.

Sometimes these run around 100v or more. Look for small mosfets on both sides
If you have a scope there should be a 40khz signal feeding the mosfets to fire the inverter from the ic (14 or 16 pin). If I remember correctly the alpine amps were
built very well. As for a car that sits I would go after board issues. I had an Alfasonic
amp in my 65 Buick and I only drove it in the summer. I had the same problem you are
having. I wasn`t getting the audio signal through the preamp. I had to crank up the input signal (1v) then It would start working. I re-soldered the preamp curcuits and that fixed it. Hot and cold ( worked on warm days) not in the morning.

A picture would help alot here.

good luck!

Cadiman

[torpex505]

Thanks, I'll try to get some pics tonight. It is definitely on the audio end. I am able to turn the amp on and even adjust settings through the optional "remote" mounted in the dash. I had another amp at one point that did the same thing and after re-soldering the RCA inputs it started working again. That was a cheap Jensen amp though. Being that this is a higher end amp, I didn't just want to start re-soldering anything without being sure.

Also, any suggestions on how I can get a solid 12V to this thing on my workbench without running a set of jumper cables to my car battery?

Thanks for you help

[Th3_uN1Qu3]

You can just use a spare ATX PSU, it wouldn't be enough to drive it at full power but it should work for just starting it up.

[torpex505]

Awesome, I didn't think that there would be enough amperage. I have a cheap $10 PSU sitting in the closet that i picked up about a year ago as a backup. I'll get it hooked up tonight then.

Thanks!

[torpex505]

Here are some pics. I took close-ups of the more heavily populated areas.

[cadiman]

I have bench tested all of my amps with an old vista power supply rated around 10amp.
as said above you only perform low level bench test for operation not a party.

Also do not ever run any amp on the bench without outputs mounted to heatsink. the mosfets in the power supply will burn up in a second (I was a punk kid then and made lots of mistakes).

I don`t like all the surfacemount ics on that amp ( never good in a car ) and can understand why to not jump into resoldering.
If you can signal trace the rca inputs with your ipod hooked up and the amp turned on ( to let the signal through). you should be able to figure out where the signal is missing.

All you need is an old cheap scope if you can find one.

[torpex505]

Cool, I'll check craigslist and local pawnshops for a cheap scope to try that out. Thanks for the info. I was able to power it on with a cheap psu, but I didn't really get anywhere with it. I tried tracing with my voltmeter but couldn't find anything.

[cadiman]

Since you have the amp out of it`s shell it is easy to check the outputs and mosfets with your meter for any shorts. You can do a quick check and look for any base/collector shorts. If you find something then you will need to remove the outputs and check each one to find the bad transister. I don`t know anything about your amp, but It should go into protect mode with a light of some kind if this is the case.
after further inspection of your pictures that board is a double printed curcuit board same as the Delcos. Anywhere there are jumpers from one side of the board to the other is where you will have a bad solder joint. Also any heavy components will have to be checked where they solder to the board. My first scope came from a garage sale and had tubes in it. You don`t need much for audio even the driver ics only run around 44 khz for the power supplies in most car amps that I have worked on.

[dirtrider383]

im new to all this hi tech stuff but my mrd is doing the same thing can u guys explain it the retard way lol it powers up fine and everything i had it working went inside came back out turend it on and nothing any help wud be nice

[cadiman]

Pictures always help!

[kaboom]

This is not an amplifier in the normal sense. It's a "class D' PWM switching amp. Not talking about the DC-DC converter here.

The final in that is to amplifiers what SMPS are to heavy linear supplies.
Fine for a sub amp where lots of power, less than full audio bandwidth, and relatively high efficiency are specified.

Those ICs will make it interesting... In the Memphis 16-500D and successors, their PWM ICs for the final had their part numbers sanded off.

Check the 7815/7915s for the opamp supplies.

-Paul

[mbates14]

Go into the amplifier's menu, and make sure output is set to ON.

I ran into this mistake once.

[torpex505]

I just wanted to give an update as the thread starter. I decided to trash the amp. I had a smaller one laying around and decided to go that route instead. Good luck to you dirtrider, hope you can figure your's out.

I did want to thank everyone who tried to help me though.


On a side note:
I find it amusing that such a pricey amp (if I remember right, I paid ~$900 for it) is being replaces by it's ancestor: Alpine MRV-T757 (which was ~$400 new).

[daRk_Kon]

it might have been the RCAs, i had a similar problem, switched the RCAs resoldered the new one and POW worked like a charm

[torpex505]

Originally Posted by daRk_Kon

it might have been the RCAs, i had a similar problem, switched the RCAs resoldered the new one and POW worked like a charm

I actually had desoldered and disassembled them, pinched the internal connection prongs together(i noticed that they were not very tight) then resoldered them. I checked the continuity and everything seemed fine on that end. thanks for the suggestion though.

[rdunnit]

I am new here and I ran into this post. I am an avid car audio enthusiast (have been ever since I bought my first car audio setup:a Kraco underdash 8 track unit and some surface mounted speakers).
I have repaired a lot of amps in the past but haven't repaired a class D yet.
One thing that I may suggest is look up Perry Babin on diyaudio.com. He is a guru when it comes to car audio amplifiers and has helped quite a few people on the diyaudio forum. I hate to see you trash an amplifier unless the board is burnt to a crisp as so often happens when people put amplifiers in a load not intended to be run. I have read of people placing amps down to as low as .125(.13 rounded) in competition!!! Crazy but then it's all about winning in competition.

Robert