Faulty Alpine MRV-T505 - diyAudio
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Old 13th December 2007, 10:59 PM   #1
Escy is offline Escy  United Kingdom
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Thumbs down Faulty Alpine MRV-T505

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.
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Old 14th December 2007, 02:43 AM   #2
jol50 is offline jol50  United States
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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.
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Old 14th December 2007, 03:09 AM   #3
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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.
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Old 14th December 2007, 10:19 AM   #4
spooney is offline spooney  United States
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My mrv-1000 did this because of an open ground trace.When I repaired the open trace the problem went away.
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Old 14th December 2007, 08:08 PM   #5
Escy is offline Escy  United Kingdom
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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.
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Old 14th December 2007, 08:08 PM   #6
Escy is offline Escy  United Kingdom
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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?
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Old 14th December 2007, 08:14 PM   #7
shagone is offline shagone  United States
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Quote:
Originally posted by 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?

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.
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Old 14th December 2007, 08:25 PM   #8
jol50 is offline jol50  United States
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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/...02/inside1.jpg
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Old 14th December 2007, 08:28 PM   #9
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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.

Click the image to open in full size.


Click the image to open in full size.
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Old 14th December 2007, 09:00 PM   #10
Escy is offline Escy  United Kingdom
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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.
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