Mackie CR3.. Anyone have this happen?

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NTStem

Joined Feb 5, 2021
9
I got a pair of CR3’s as part of my first home studio setup. Shortly after the warranty was up (how lucky,) they started cutting out unless I could find the perfect position of the “powered speaker” switch on the backplate. I held onto them for a while after getting some JBL’s and decided to open the powered speaker up the other day.

Honestly, I’m surprised they still worked even as poorly as they did. What I’m wondering is; would it be possible to repair this? I’ve got a decent bit of knowledge with circuitry, but I’ve never dealt with a board scorched like this.

I know it would be a rather extensive project with replacing multiple surrounding components as well as the swollen cap. However... Would it be possible to replace those faulty/damaged components without a new board?
 

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Thread Starter

NTStem

Joined Feb 5, 2021
9
There are electrolytic capacitors showing that need to be replaced.
C72, C77, C81.
C81 is clear, I’m guessing C77 is the 35v4700μF that is swollen. Which is C72? I can’t see so much of the board because of their stupid glue.. Also, would you happen to know the ratings of these? Once C72 is identified it shouldn’t be a problem as well as C77 but there is no label left on C81.. It wasn’t even in the cabinet when I initially opened this up.
 

MrChips

Joined Oct 2, 2009
23,524
C77 is 4700μF 35V
C72 is 8.2μF 50V non-polar, the one with the brown crud that leaked out under it.
C81 is 100μF 16V, that is blown to smithereens
 

Thread Starter

NTStem

Joined Feb 5, 2021
9
C77 is 4700μF 35V
C72 is 8.2μF 50V non-polar, the one with the brown crud that leaked out under it.
C81 is 100μF 16V, that is blown to smithereens
I actually just noticed that the 8.2μF is 100v.. Much less common (at least on any suppliers I’ve checked) to be stocked.
 

MrChips

Joined Oct 2, 2009
23,524
C72 is in the low-pass filter circuit to the woofer. I think 50V would be ok but you can go higher if you wish. The difficulty would be in finding non-polarized capacitors at those values.
 

Thread Starter

NTStem

Joined Feb 5, 2021
9
C72 is in the low-pass filter circuit to the woofer. I think 50V would be ok but you can go higher if you wish. The difficulty would be in finding non-polarized capacitors at those values.
I’m rather confused.. I’ve never come across these markings. This is the opposite side of the board at the C72 leads. “zzz” marked between leads and a (+) beside one of the leads. If it is a non-polar cap (which it does not have the negative lead marked on the casing,) why would there be a positive marking on the board? (Sorry for not marking the picture.. It is the one straight to the right of the top of that zip-tie.)
 

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