Possibly Fried Alpine MRV-F352 5 channel Car Amplifier

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So I am a relatively novice when it comes to installing car audio. Anyway, I've hooked up my 9 year old Alpine amplifier, and it seems to be malfunctioning.

The first problem is that the power light never fully shuts off. When the key is out of the ignition, the power is about 50% full brightness. When the key is turned to ON, it fully brightens. I've checked and double checked the blue remote on wire, and it's hooked up as it should be. What could be causing this?

The second problem, and the far worse problem, is that the 5th channel barely outputs any power to my sub. The other 4 channels work fine for my component speakers and coaxials. After deciding to open up the amp, I noticed at least one transistor that seems to have fried. What could have caused this?

Is it worth it to even try to repair it, or should I just toss it and buy a new amp? Thank you for your time.
 
They are fairly good amps IMO. The sub channel is a bridged channel in the one I have but think it is a 353 model. Look up the manual for it, I found one for mine free. Anyway, the manual says 4 ohms on the sub channel not 2 and that is typical for bridged. If someone ran it at 2 that may have blown it I am not at all sure if they can handle 2 ohms on sub....they can on highs like a normal 4ch. In mine the sub is its own two bridged channels and has its own power supply, is easy to see. Yours could be different, but many of the mrv are similar designs. I'm not sure if I have photos of mine.
 
I will try to take it apart again and take a photo of the entire board and some close ups of the portion that looks fried. The pins were even bent back from the transistor chip itself.

Hopefully I make some sense, I'm a novice when it comes to circuit boards.
 
I fixed an MRV-F407 (4 channel) Alpine amp with similar issues. The pair of MOSFETS in the output stage for one channel had failed. Replaced them and it works very nicely. They are good amps and worth saving IMHO.

The fact that some channels work siggests the power supply is working fine.

What have you conencted the remote turn-on line to? could it be that it's not dropping completely to zero volts with key off?

Kevin
 
You can always take a meter on ohms and trace the speaker terminal to the output on the sink. If the sub channel is bridged you will have two pair of output transistors, one pair will likely have the right leg connected to one sub speaker terminal and other pair the other terminal. An unbridged channel will have one side of a speaker common and other to a pair (more than a pair in larger amps). Ignore the + and - for this purpose unless it is an old unbridgeable amp.

Ampguts has no pics of a 5ch I could find, the 757 is a tripath and much different.
 
I've only connected the remote on lead to the blue/white wire that comes from the back of my Head Unit. I was having similar problems with my old setup, so I think that remote on issue is old. I just never messed with it before and was just going to try to fix it in my new setup. I guess the problem might be an internal one.

Thanks for all the suggestions so far. I will take some detailed photos and post them on here by the weekend and hopefully we can get somewhere with fixing this thing. I definitely enjoy taking electronics apart and fixing them. I just do not have a whole lot of experience, so I will probably need some "hand-holding" once I get those photos up here.

My background is basic soldering of wires for modifications onto mainboards, but never really replacing entire chips, transistors, etc.

If I don't make any sense, it's because I'm an idiot....:confused:
 
Just need to find the broken parts and replace, not that bad, but hard to do when we can't see it. If I have time I will dig mine out it is likely the same but I can't find any photos must not have taken any.

Keep at it and you will only be half an idiot like me:D It can be fun at times. I've done enough alpines now to forget how many, but I like them for some reason.
 
Here are a bunch of photos of the inside, and I took a closeup of the area where it looks like something fried. Also, I didn't take any of the underside of the board.

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That is like mine. In the first photo the upper right section is the sub amp, its PS blew. The orange and brown wires that go to outputs next to it are the two bridged channels for the sub. Test those 4 outputs they may have shorted the PS like Perry suggests. Check the drivers too.
 
Perry Babin said:
The basic repair page (link below) will help if you're new to repair work.


While I waited for the moderators to approve my replies, I did read some of the information on the repair page. I definitely will be able to test the resistors using my multimeter. I have very basic soldering skills, but have usually only soldered wires together, or soldering wires onto a circuit board, but have never removed and/or replaced chips on the board. This may be way over my head.

I'm open to learning and fixing it myself, but if in your opinion this would be way too difficult for a novice to repair, I'm ok with just taking the loss.
 
Test Q464 and the other three large transistors towards the blown ones. Those are the outputs for the orange and brown wires, if you test ohms you will find those wires connect the outputs to the sub speaker terminal (through the large white resistors that have very little resistance). Poke around with the meter or look at the traces to see what is what. Check Perry's page on testing transistors and the amp repair pages. A transistor may blow and not show it too. If the outputs shorted they could/did blow the power supply.

Order some solder wick and maybe get a sucker too, or radio shack has it.
 
Just wanted to post a follow up. I ran some tests with a junk multimeter I had lying around.

One of the burned resistors had readings up 800+ ohms, and it did never really settled down. The other one read right around 74/75 ohms.

I'll probably have to grab a better multimeter and re-run the tests sometime this week. Sorry for the delay, but I appreciate all the help so far. Please bare with me. Thanks again!
 
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