Rainbow Dream 1 amplifier going into protection mode, burning fuses

[Terrum 10+ year member]

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.

Indeed, but finding out the cause of it is what I'd like to do, if possible. I have a digital multimeter so I can try probe some things if you or anyone else reading this has any suggestions.

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

It's a mono amp so 1 channel (sub only amp).

You could be right, but I'm still not entirely convinced. Just looking at a random irrelevant thread I've seen there's a store photo of the 'donuts' and one of them looks similar where there's not a complete raveling of coil. https://www.caraudio.com/threads/what-gauge-cable-for-this-amp-please-help.608836/#post-8760677

 

[Buck 5,000+ posts]

Indeed, but finding out the cause of it is what I'd like to do, if possible. I have a digital multimeter so I can try probe some things if you or anyone else reading this has any suggestions.


It's a mono amp so 1 channel (sub only amp).

You could be right, but I'm still not entirely convinced. Just looking at a random irrelevant thread I've seen there's a store photo of the 'donuts' and one of them looks similar where there's not a complete raveling of coil. https://www.caraudio.com/threads/what-gauge-cable-for-this-amp-please-help.608836/#post-8760677

Have you ever seen a burnt subwoofer coil that's coming unraveled?

 

[Terrum 10+ year member]

Have you ever seen a burnt subwoofer coil that's coming unraveled?

I haven't unfortunately, but the coil I randomly came across in the URL I posted looks similar to it so I assumed that might be normal.

Regardless of whether it is or not, I'm still open to any other suggestions to try diagnose this further

 

[Buck 5,000+ posts]

I haven't unfortunately, but the coil I randomly came across in the URL I posted looks similar to it so I assumed that might be normal.

Regardless of whether it is or not, I'm still open to any other suggestions to try diagnose this further

I'm not sure how you would measure anything inside of the amp without hooking up the power wires. Since the fuses blow, I don't think there's much that you can do there. There's many different types of electricity at all different locations on that board; that's what an amp does. You might send these pics to Rainbow themselves, and see what they say, or any company or individual that's involved with electronic repairs. Amp repairing is probably one of the most difficult areas of audio; amps are complicated, and electricity is probably the hardest thing in the world to understand.

 

[Terrum 10+ year member]

I'm not sure how you would measure anything inside of the amp without hooking up the power wires. Since the fuses blow, I don't think there's much that you can do there. There's many different types of electricity at all different locations on that board; that's what an amp does. You might send these pics to Rainbow themselves, and see what they say, or any company or individual that's involved with electronic repairs. Amp repairing is probably one of the most difficult areas of audio; amps are complicated, and electricity is probably the hardest thing in the world to understand.

I'd have hoped if it was something like a short, that I could check some tracks/components with the continuity setting of my meter.

Finding someone to service it here in the UK is proving difficult. I've got in touch with a few people but only time will tell if they are actually willing to help.

Good shout about sending the pics to Rainbow themselves though - I might do just that.

I'll keep this thread updated if anything new happens, otherwise as always any other input/suggestions are always appreciated

 

[AnthonyO 10+ year member]

Isn't that a blown resistor of some type

 

[Terrum 10+ year member]

Isn't that a blown resistor of some type

As far as I can tell, no. If you are referring to the yellowing, it is soaked with the same yellow gel along with many other parts of the board. I could try draw an outline of all the parts that are covered in that yellow stuff if it would help.

 

[audiobaun 5,000+ posts]

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.

Sounds like it was installer error. More than likely power touched ground damaging Power supply.. Just my 2 cents.. Or could have ran it it a lower ohm load and damaged some Caps, and or Mosfets. About all I can think of. But Fuses not popping as they should when in contact with supply generally tells me.. Power Supply issue.. Power and Ground met at one point and damaged power supply(Installation Error/ Rookie)

 

[AnthonyO 10+ year member]

As far as I can tell, no. If you are referring to the yellowing, it is soaked with the same yellow gel along with many other parts of the board. I could try draw an outline of all the parts that are covered in that yellow stuff if it would help.

No, if you look at R86 and R83 you can see the resistor. But on that one Q20 it is solid black. Look at Q21.

 

[Terrum 10+ year member]

No, if you look at R86 and R83 you can see the resistor. But on that one Q20 it is solid black. Look at Q21.

Might be, in that case. I'm still not entirely convinced though. I had as close of a look as I could at it but it doesn't look damaged in any way. I think the yellow gel might have possibly eaten away at the text on it though (if there were any on it in the first place).

Although something very odd I have noticed is that C7 is basically just a melted spot with no tracks. I wonder what in the world that could be (or what it was).

Either way, Rainbow still haven't gotten back to me yet but I will continue to keep this thread updated as I go along

 

[Terrum 10+ year member]

Sounds like it was installer error. More than likely power touched ground damaging Power supply.. Just my 2 cents.. Or could have ran it it a lower ohm load and damaged some Caps, and or Mosfets. About all I can think of. But Fuses not popping as they should when in contact with supply generally tells me.. Power Supply issue.. Power and Ground met at one point and damaged power supply(Installation Error/ Rookie)

Thanks so much for your input. I truly suspect it is an installation error. So many signs, even the buyer himself appeared sketchy. Returned it almost a month later, dropped it off without asking, said a friend dropped it off but I checked my video doorbell and the face of the guy matches the face he has on his eBay profile, had gains set high and bass boost on despite him saying it was his first 'power on test' and I dispatched it with gains and bass boost off. Oh well - the joys of selling on eBay

 

[Buck 5,000+ posts]

Yeah, ebay has some messed up rules.

 

[Name'sDEEZ]

I know im late but did you check the bottom part of the board maybe burnt tracks. I recently resolderd a visonik that looked perfect untill i flipped it over and a giant ground rail on the board just missing a chunk. I think the dude just over powered your amp (why the gain is all the way up) and the coils unless you can wiggle them they should be good. Some caps even though they look good could be exploded. Only way to test would be to lut fuses on it and power it on but first flip over and inspect that side first