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Subwoofer immediately blows the fuse - Dynamo 1000W (discontinued)

MartinLogan Owners (MLO)

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Kam Lo

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I have Martin Logan Dynamo 1000w subwoofer (currently out of warranty and item discontinued). I noticed it was off (not sure for how long it has been like that). Checked the fuse, and sure enough it was blown (LF T5AL250VP).
A friend of mine checked the backplate, turned out the slot TH1 (SCK-048) is completed burned. See pic attached. ML customer rep asked $300 to replace with a new backplate but only comes with one year warranty. I am debating should I continue DIY to repair it (with my limited knowledge) or switch to a different brand? I asked the ML rep (Ron Hayes) in exchange for a few emails to try to get the schematic of my subwoofer dynamo 1000W. He said he doesn't have it. As a prestigious brand and hi-end audio manufacture, a schematic diagram of such product should be available within ML shop and they refuse to provide one. Anyone input and help here is greatly appreciated.
 

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ttocs

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Where are the two large capacitors that look like they're missing? Looks like the black adhesive is where they used to be.
 

Kam Lo

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my friend is a car mechanic and he removed and tested them, both findings were fine.
 

Kam Lo

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my concern is that even I replace SCH-048 and a new fuse, there might be something else to trigger malfunction of the backplate.
 

Robert D

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my concern is that even I replace SCH-048 and a new fuse, there might be something else to trigger malfunction of the backplate.
I had a sunfire sub that kept blowing fuses. I tossed it out. Prior to that i had sent it back to them to have it refreshed
 

Kam Lo

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sounds like ML owners don't have high hope to repair its broken speakers other than buy new or replacement.
 

Luna

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Hi
this part (thermistor)protects your sub from AC overloads so once removed the fuse should not burn again, if not you have a problem further, output short or High frequency power supply. to be sure not to damage anything, put a 60 watt bulb in place of the fuse and if it stays on at full power, you have a problem. if the sub is in good condition I recommend changing the plate amplifier
 

Kam Lo

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Thanks for everyone's input here. I guess my last option will be replacing the backplate entirely. Overall my subwoofer is in excellent condition.
 

Robert D

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sounds like ML owners don't have high hope to repair its broken speakers other than buy new or replacement.
It seems like they don't concentrate on servicing the older models like my depth I. I contacted them about my issue and didn't get any help except for some troubleshooting tips. I have a feeling they don't have parts any more for it.
 

Kam Lo

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It seems like they don't concentrate on servicing the older models like my depth I. I contacted them about my issue and didn't get any help except for some troubleshooting tips. I have a feeling they don't have parts any more for it.
I feel your pain. We don't have much love from ML for the older models. it really depends how old is your speaker. I purchased my dynamo 1000W around April 2017 and my warranty just expired 7/8months ago. To order a new backplate will cost $300 plus shipping. That is my last choice rather than DIY for the root cause.
 

Robert D

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I feel your pain. We don't have much love from ML for the older models. it really depends how old is your speaker. I purchased my dynamo 1000W around April 2017 and my warranty just expired 7/8months ago. To order a new backplate will cost $300 plus shipping. That is my last choice rather than DIY for the root cause.
Well, thats not bad since they at least have the part. If I was 100% sure that was what is broken then I would order that part. I dont think they have any parts for my Depth i. It is a lot older.

They seem to support their floor standing speakers very well. Ive got them making new panels for my Prodigy speakers and those are from 2000, so 20 years old. Im impressed with that.
 

Kam Lo

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Well, thats not bad since they at least have the part. If I was 100% sure that was what is broken then I would order that part. I dont think they have any parts for my Depth i. It is a lot older.

They seem to support their floor standing speakers very well. Ive got them making new panels for my Prodigy speakers and those are from 2000, so 20 years old. Im impressed with that.
just placed an order for a new backplate.
 

spkrdctr

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That sounds like a wise choice. Something besides what you found is causing it to blow. $300.00 is a great price! Let us know when you have it up and running again.
 

Kam Lo

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That sounds like a wise choice. Something besides what you found is causing it to blow. $300.00 is a great price! Let us know when you have it up and running again.
will do and keep you all post.
 

Kam Lo

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I had the new backplate replaced over the weekend, it is working now and my Dynamo 1000W is as good as new. Hopefully, it won't break again after the warranty!
Thanks for your input and suggestions.
 

Robert D

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I had the new backplate replaced over the weekend, it is working now and my Dynamo 1000W is as good as new. Hopefully, it won't break again after the warranty!
Thanks for your input and suggestions.
How long is the warranty on the new part? 12 months?
 
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