Faulty Alpine MRV-T505

[Escy]

Hi guy's, new here. I've had the mis-fortune of buying a faulty amp. Well, I think it's faulty, tried it on a few cars and it's not working. The power light comes on all the time and when you connect the battery, I think this is normal as when you turn the headunit on, the light get's brighter. It's just a standby light. So all of that seems fine.

The problem is, i'm not getting any sound output from it. I took the heatsink off it and couldn't see any obvious damage on the board. I didn't look at the other side of it though.

Does anyone have any ideas, are there any common breakdowns on Alpine units? It could just be something simple like a setting on the amp.

 

[jol50]

You have verified power and ground, remote is good to the amp? Fuses good? Speaker wires good? Did you move all the controls around? Then if you are stuck with the amp you can either sell it or take the cover off and check some simple stuff with a meter if you want. People here can tell you to check for the usual things if you want to get into it.

 

[Perry Babin]

I don't have the manual for the 505 and I've never worked on one but I don't think it's normal for the light to remain on when the remote voltage isn't applied. If the light remains lit with the remote turn-on wire disconnected, I think you have at least one defective transistor.

 

[spooney]

My mrv-1000 did this because of an open ground trace.When I repaired the open trace the problem went away.

 

[Escy]

I would I go about looking for an open ground trace?

I removed the remote turn-on wire and the light stayed on.

Jol, I think it's faulty as it's been tried on a few cars and not worked.

That said, I tried my friends sub and amp on my car and that still didn't work.

 

[Escy]

just to add, i've started stripping it, i've checked for continuity between the ground and power pins and i've got a little beep. It's happened a few times, and not for very long. I'm thinking it shouldn't do this?

 

[shagone]

just to add, i've started stripping it, i've checked for continuity between the ground and power pins and i've got a little beep. It's happened a few times, and not for very long. I'm thinking it shouldn't do this?

the beeping is the protection diode. this is normal. look for a blown open trace on the bottom of the board near the power entry location.

 

[jol50]

You need to look at the bottom of the board unless it has the traces for ground on the top. Look at the ground terminal and follow the circuit, look for a ground screw to the case that grounds the ground circuit. Then look for it to be burnt apart someplace.

My 1002 has a big winding in the corners that power goes through, and one has the frame grounded to the other then to the case with a little tab. The one without the tab on other side had ground blown under it. In this pic it would be that square thing way up in the top left corner, under that. I never ran it that way though, so don't know if it affected it.

You might be able to take a few screws out and there is bars under all the transistors that come off case if its like mine. I didn't do that, but the paste on mine has to be all cleaned off because it separated.

http://ampguts.realmofexcursion.com/Alpine_MRV-1002/inside1.jpg

 

[Perry Babin]

You shouldn't have continuity between the ground and B+ terminals. Check for continuity between the ground terminal of the amp and the third leg of the power supply FETs. You should have ~0 ohms between them. If you had the red meter lead on the positive terminal and the black lead on the ground terminal, the meter would have beeped because the capacitors weren't charged. After they charged (from the voltage applied by the meter) above ~0.1v, the beeping would have stopped.

Open traces are generally easy to see. They will look like one of the 2 images below.

 

[Escy]

I only looked at the front of the board. I couldn't see anything obvious. I've fitted it back into the car now. If I don't get any joy, i'll remove the whole of the casing and look at the back of it. Thank's for all the pictures and information.

I managed to find a manual for it and i've worked out what all the correct settings I need. What i've noticed on my car is that the remote doesn't seem to be working. On my friends car, with my amp, the power light got brighter when he turned his stereo on. On mine I think it's staying the same. How can I test it, am I ok to bridge the live wire on the amp to the remote wire?

My remote wire is quite pathetic, it's a really thin one that runs through the middle of the RCA leads. Last time I checked, it was showing a voltage getting through to the amp. The terminal on the amp is big, the same size as the live and ground terminals. Maybe my remote wire can't provide the juice the amp needs? It is designed to be a remote wire though.

Thanks for all your help so far guy's, this seems like a great forum. I've also got a old school Pioneer GM-3000 I might ask about next, once I get this amp working.

 

[spooney]

Theres not much point of putting it back into the car if its damaged. You could even end up with more problems.If your lucky the ground trace might be the only problem and its an easy fix.You can get the amp completely disassembled in 10 minutes or less.The small remote wire most likely isn't causing any issues.The amp doesn't really pull too much current through that lead. Its just supplying a signal that lets your amp know when to turn on.

 

[Perry Babin]

If the light isn't getting brighter in your vehicle, you may have multiple problems.

To check the remote output if the head unit, use a multimeter set to DC volts. Place the black lead on a known good ground (the ground terminal of the amp or the case of the head unit -- if/when you check the voltage at the back of the head unit). You should have ~12v with the head unit on and ~0v with the head unit off.

If the remote output is burned out, for testing you can jump from the B+ terminal of the amp to the remote terminal of the amp. Use a jumper with a 1 amp inline fuse. Disconnect the remote wire from the remote terminal of the amp before jumping from B+ to remote.

 

[Escy]

Perry, I checked the voltage when I 1st connected the remote wire, I did scotch lock it though (temporary measure) so maybe that's failed, will re-check it in the morning.

What exactly is the B+ terminal on the amp?

I found someone selling the same model amp on ebay so i've asked them to confirm about the power light. If thats how it's supposed to be, the amp may actually be fine.

 

[Perry Babin]

B+ = battery positive

 

[Escy]

Ok thanks, can you tell i'm a novice?

Does the remote lead not supply more than 1 amp to the amplifier? If so, I won't be worried about the poxy little cable for it.

 

[Perry Babin]

The current required by the remote terminal is generally 0.025 amps or less.

The 1a fuse is to protect you and the vehicle in case you short the jumper to ground or the case of the amplifier.

The small wire can deliver sufficient current to the remote terminal but small wires tend be fragile and can make a system unreliable over time.

If you don't have a fuse in the remote lead (at the back of the head unit), you should install one. To protect the head unit's remote output drive circuit (after it's repaired), you should use a 1/2 amp fuse.

 

[ppia600]

Will the power light stay on if you have the rca leads disconnected? Some amps will try to power up if the main ground input terminal is cracked loose from the circuit board and its trying to get ground through the preamp circuit. Try this:

Connect only the main + and - terminals and nothing else to the amp.. does the led stay on dimly? Do not connect the remote lead or rcas. If the led doesn't come on at all with only the two main power leads connected, you may have a bad solder joint at the negative connection to the circuit board.

 

[Escy]

Thats what it's doing, i'll have to take it back apart again today and have a proper look at it.

 

[Escy]

I've opened it up now. Can't find any open traces, I does have a fair bit of rust on the back of the circuit board, especially be the fuse. Could rust be enough to ruin things?

I'm trying to take pictures but my phone doesn't have a macro feature and they are coming out rubbish.

 

[Escy]

I've found something thats made the board go black. I don't know what it's called so i'll describe it. Looking from the bottom of the curcuit board. It's a little bar, there are loads of them, this one is black in colour and has 470 printed on it. It cracked off the board when i poked it.

When I turn the board over, there are 2 resistors that run over it, it looks like this bar thing could attach the middle of the 2 resistors.

I'll get some pictures when my house mate gets home.

I can't tell what circuit they are part of but there are in the corner where the remote, B+ and ground are.