Rainbow Dream 1 amplifier going into protection mode, burning fuses

[Terrum 10+ year member]

I sold a Rainbow Dream 1 amplifier about a month ago, it was returned to me as faulty. With no speaker wires attached and gains at their lowest, bass boost off etc, the amplifier goes straight into protection mode as soon as it is powered up, and starts burning the legs off of the fuses. It doesn't actually blow the fuses, it just burns the legs off for some reason. The amp uses the ordinary kind of fuses you would see in fuse boxes of most vehicles.

Mind you this amp was serving me just fine for the two years I had it, never over-run. I know I'll probably just have to cut my losses but for my own curiosity I would like to find out what is wrong with it, and if possible figure out if it was damaged during delivery or by user error.

As I'm in the UK, finding someone to service the amp is proving difficult so I am potentially looking into diagnosing it myself at least (and possibly repairing it if I can). I'm definitely not an electrician, but I have replaced/resoldered resistors/capacitors before. I also have a multimeter but I wouldn't exactly know where to start on how to find out if there's a short circuit somewhere (to find which component is faulty) or what I should do.

Any advice is extremely appreciated and of course any input/discussions on this situation is also appreciated! Many thanks

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[Buck 5,000+ posts]

Have you opened the amp up to take a look inside?

 

[Terrum 10+ year member]

Have you opened the amp up to take a look inside?

Hi Buck, hope you're well

Not just yet. I'm currently just at discussion stages to see what anyone here thinks before I consider opening it up. First off I wouldn't really know what to look for, and if I were to start using a multimeter on any of the components or tracks, I would yet again have no idea where to start

I guess a good starting place would be to look for any visually burnt out components or anything that looks out of the ordinary. I'm just super curious as to whether it's more common for amplifiers to fail by physical damage, user error or just by themselves.

 

[Bobbytwonames 5,000+ posts]

Hi Buck, hope you're well

Not just yet. I'm currently just at discussion stages to see what anyone here thinks before I consider opening it up. First off I wouldn't really know what to look for, and if I were to start using a multimeter on any of the components or tracks, I would yet again have no idea where to start

I guess a good starting place would be to look for any visually burnt out components or anything that looks out of the ordinary. I'm just super curious as to whether it's more common for amplifiers to fail by physical damage, user error or just by themselves.

I sent two amps back to Sundown lately and neither of them was my fault. My thinking is if it doesn't smoke and burn up immediately and I installed the amp at the recommended ohms than it was an amp problem.

 

[Terrum 10+ year member]

I sent two amps back to Sundown lately and neither of them was my fault. My thinking is if it doesn't smoke and burn up immediately and I installed the amp at the recommended ohms than it was an amp problem.

The thing is, I used the amp for a few years without any issues and it only stop working as soon as I sold it on. I even tested it just before dispatching it. Either I'm really unlucky, or it was internally damaged somehow during delivery, or the buyer installed it incorrectly.

I'll open it up and snap some photos at some point today if I can. Of course if I see anything obvious I'll reference that also.

 

[Buck 5,000+ posts]

I think that's the only way that you're going to be able to figure out what's going on. Snap some pics of the inside and post them up.

 

[Terrum 10+ year member]

I think that's the only way that you're going to be able to figure out what's going on. Snap some pics of the inside and post them up.

Luckily I just finished opening it up and inspecting it

I'll attach the photos below but I can't really find anything out of the ordinary. There's some yellow solid gel underneath some of the capacitors which has me concerned, especially as it's over a lot of the other components and the fuse connections but it could also be normal?

Again I'm not 100% sure what I'm looking for but I can't see any burnt/blown components of any kind. The last 2 photos are to show the yellow gel that's gone over to the fuse connections, and also the burnt fuse slots because why not I guess

 

[Buck 5,000+ posts]

Nvm, slow loading.

 

[Buck 5,000+ posts]

View attachment 32152

Do you see the metal there on the "top" fuse bar where it's close to that wrapped coil? You see how that top one looks like a different color than the other bars there? One looks copper-ish (bottom one), and the top one looks more raw silver-y metal-like.

Where that coil end goes into the board, and where the top long fuse bar goes into the coil there; is that metal looking stuff supposed to be on top of the board there? I'm not sure if that metal there is supposed to connect to the end of that coil like it is, but idk.

Just look at the plating on the metal bars that lead into the fuse clips-they seem to be different colors. That could indicate damage, or it could just be the angle of the pics. I am not an amp repair man by any means, but there does seem to be discoloration there between the bars that lead to the fuses, which could indicate a heat related problem, like a short.

 

[Buck 5,000+ posts]

I wonder if that is silver solder that got too hot and melted to connect that coil to the top fuse bar or if that's how it's supposed to be connected.

All of the goo on the inside of this amp seems kind of strange. I've never seen so much stuff in between parts and the board itself.

One of those giant donut shaped copper coils looks damaged. Just saw that. Look at the top copper coil, and then look at the bottom one. It's half-black and looks like it's coming apart.

 

[Buck 5,000+ posts]

View attachment 32149

View attachment 32150

Look at the copper donut coil on the bottom there- it's coming apart and half of the wiring is black.

 

[Buck 5,000+ posts]

I'm just stating what I see. That bottom donut coil definitely looks like it's been burnt and is coming unraveled, to me.

 

[Terrum 10+ year member]

Thanks so much for your input Buck

I think the yellow gel everywhere is normal, because I noticed that same gel seems to be on the screws and on some resistors as well. I don't think anything would have leaked because the amp has always been installed upright (the components shown in the photo would have been facing down, so if anything leaked, it would surely go onto the plate that covers this board?

As for the metal bars on the fuses, I think one of them looks discoloured because the gel is also covering the two bottom fuse bars.

I think the coils on the bottom 'donut' are meant to be black. Looking at a photo of the only Rainbow amplifier I can find opened, these ones appear to have black ones too: https://www.amp-performance.de/cach...rainbow/rainbow-kw4150/gal_0/dscf0026_107.jpg

I can definitely see that it looks like it's coming apart though. Assuming this is the issue, what would you think the cause of that would be? I'd hate to know now that the buyer probably abused it because, well, I already refunded them

Seeing as it came back to me a month later with gains set high and bass boost on, I have my suspicions. They also told me they have 20+ years experience with car audio. Now I have far less experience than that but even I know if I were testing an amp I wouldn't have my first power on test with gains high and bass boost on

 

[Buck 5,000+ posts]

It seems like the amp is blown and there's a short somewhere inside. That's the only reason the fuses would blow immediately like that, from what I know.

 

[Buck 5,000+ posts]

I'm pretty sure those two donut coils should look exactly the same. How many channels is this amp?