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Old 01-25-2021, 03:16 PM   #1
robross0606
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Default Definitive Technology Subwoofer repair

I have a Definitive Technology compact subwoofer that went belly-up and started buzzing constantly instead of producing any sound. After research, I decided to try replacing the primary 6800uf 80v capacitors . After replacing the caps, the behavior has changed, but not really for the better. Instead of getting a constant buzz, I get a periodic buzz/pop/burp sound. Hard to describe, so I posted a video clip:

https://drive.google.com/file/d/12tS...ew?usp=sharing

I apologize for some of the background noise which is a clothes dryer in the next room and not coming from the amp. The only sound coming from the amp is the very loud "burping" noise starting around the 00:41 mark in the video.

Unless I'm crazy, the sounds starts out slow and picks up repetitive speed as it remains powered. If anyone has any suggestions for what might be wrong and whether it is reasonably fixable, please let me know.

Last edited by robross0606; 01-25-2021 at 04:43 PM..
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Old 01-25-2021, 03:47 PM   #2
madan1
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Default Re: Definitive Technology Subwoofer repair

The google drive link requires sign in... make it public or upload it somewhere else. Also, upload some HD photos of the amp board.
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Old 01-25-2021, 03:51 PM   #3
robross0606
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Default Re: Definitive Technology Subwoofer repair

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Originally Posted by madan1 View Post
The google drive link requires sign in... make it public or upload it somewhere else. Also, upload some HD photos of the amp board.
Apologies. The link should be accessible. now.
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Old 01-25-2021, 04:24 PM   #4
R_J
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Default Re: Definitive Technology Subwoofer repair

Upload the pictures to the forum using Go Advanced, then click the paperclip to attach the pictures. What's the model number?

Last edited by R_J; 01-25-2021 at 04:25 PM..
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Old 01-25-2021, 04:25 PM   #5
robross0606
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Default Re: Definitive Technology Subwoofer repair

Quote:
Originally Posted by R_J View Post
Upload the pictures to the forum using Go Advanced, then click the paperclip to attach the pictures. What's the model number?
Will do as soon as I can get some HD pictures of the board.
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Old 01-25-2021, 04:35 PM   #6
madan1
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Default Re: Definitive Technology Subwoofer repair

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Originally Posted by R_J View Post
What's the model number?
It is pro sub 800... and it looks like there are at least two versions of that model.
From the pics in the internet also looks like a class a/b amp.


ps here is an SM for another DT sub.. I'd guess, they use the same main idea thru the majority of their models. <--- WRONG, this SM is for a sub with STK4050, while the OP's uses descrete amp.
Attached Files
File Type: pdf definitive-technology_pf18_subwoofer_sch.pdf (92.7 KB, 5 views)

Last edited by madan1; 01-25-2021 at 04:43 PM..
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Old 01-25-2021, 05:28 PM   #7
R_J
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Default Re: Definitive Technology Subwoofer repair

If the main caps were replaced and now you have a different problem, I suspect this is a double sided board and the feed-tru's were pulled out with the original caps. remove the new caps and inspect the traces for damage
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Old 01-26-2021, 08:04 AM   #8
robross0606
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Default Re: Definitive Technology Subwoofer repair

Quote:
Originally Posted by R_J View Post
If the main caps were replaced and now you have a different problem, I suspect this is a double sided board and the feed-tru's were pulled out with the original caps. remove the new caps and inspect the traces for damage
If the traces are indeed damaged, is that reasonably fixable or is the unit basically shot? If it wasn't obvious already, I'm not an electronics expert.

This unit was dead already, so I figured I would give it a shot before it goes in the trash.
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Old 01-26-2021, 09:23 AM   #9
budwich
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Default Re: Definitive Technology Subwoofer repair

the best way to determine if your work is OK, would be to post a picture of the circuit area that you "disturbed" showing as much detail as possible of both side of the board / area. Based on my limited experience, you may not have found the problem capacitor or your repair, as discussed might need "help".
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