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Old 10-29-2011, 01:25 PM   #1
electronicnub
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Default Infinity PS-12 Powered Subwoofer Fired Amplifier

I have this Infinity Powered Subwoofer and it still works but doesn't have the power it used to and it also has a buzzing sound when on. I have disassembled it and took out the amp circuit board and found about fout caps that seem to be buldging, the back of the board is burnt under one the caps that is buldging, and there was deffinetly a burnt smell. I have done alot of research and this seems to be a common problem for this model.
Can anyone tell me friom looking at the pictures if repair is possible. I have basic soldering skills and have repaired a Dell LCD Monitor by replacing the bad caps. Any help would be great. Thanks
Also I am not great at idendtifying the caps, can anyone give me any info on the type of caps I should replace these with. I have purchased from Digikey before.
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Last edited by electronicnub; 10-29-2011 at 01:32 PM..
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Old 11-11-2011, 08:51 AM   #2
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

From the looks of the board I think that you could repair it. I would clean the white ash off and make sure the traces are Okay. If not, you could try running a jumper to replace it. After you replace the capacitors I would put a conformal coating over the area to keep it from shorting out again. Clear nail polish would probably work for the coating.
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Old 11-14-2011, 03:39 AM   #3
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Are you sure that the 2 black capacitors to the right of the heatsink are actually bulging? It looks like they have a rubber cap over them. Try pressing down on the top of these to see if it's just a domed rubber cap.

It's hard to reccomend replacements without knowing the values. Can you read whats on the 2 capacitors that overheated?
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Old 01-07-2012, 06:18 AM   #4
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

not sure if the o.p is still watching but i have one of these on the bench now and can look at whatever.the bulgers are np type.all of the others must be replaced too.the only ones still ok were the main filter caps.these things run hot.even degraded the plastic panel and makes the whole unit stink.
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Old 01-07-2012, 01:32 PM   #5
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

On a passively cooled amp with the main filter caps right next to a big heatsink, I'd replace them anyway while the amp was open and the soldering iron was hot... unless I already had all the other caps but not suitable replacements for those two.
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Old 08-05-2012, 04:09 PM   #6
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Mine is damaged exactly in the same places!
I will be ordering the filter caps. I removed them and found that the brown goo at the bottom of the cap is the electrolyte oozing out!

The other caps you show will be replaced as well as the fuse.

I'll let you know if that worked.
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Old 08-06-2012, 07:23 AM   #7
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

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Originally Posted by BlueDog99 View Post
Mine is damaged exactly in the same places!
I will be ordering the filter caps. I removed them and found that the brown goo at the bottom of the cap is the electrolyte oozing out!

The other caps you show will be replaced as well as the fuse.

I'll let you know if that worked.
Make sure to buy good brand name ones too, such as Panasonic, Nichicon, Rubycon, Nippon Chemi-con, or Sanyo.
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Old 11-24-2012, 03:12 PM   #8
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Quote:
Originally Posted by BlueDog99 View Post
Mine is damaged exactly in the same places!
I will be ordering the filter caps. I removed them and found that the brown goo at the bottom of the cap is the electrolyte oozing out!

The other caps you show will be replaced as well as the fuse.

I'll let you know if that worked.
I also have a PS-12 with the same cap damaged as the OP's.
It's proving very difficult to find a 6.8uf 100v NP cap.
Can I replace it with a 10uf 100v NP without damaging other parts down stream?
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Old 11-24-2012, 03:24 PM   #9
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

That cap is likely in the signal path (hence why it's of the non-polarized type), the only thing that can happen from using a larger value is more bass. A 10uF replacement will be fine.
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Old 11-24-2012, 03:39 PM   #10
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Quote:
Originally Posted by JCnBoys View Post
I also have a PS-12 with the same cap damaged as the OP's.
It's proving very difficult to find a 6.8uf 100v NP cap.
Can I replace it with a 10uf 100v NP without damaging other parts down stream?
Are they film caps?

If so then Digikey has some, though it might be in the power supply circuit instead of the signal path so you might want to measure the voltage across it before going with a lower voltage value, otherwise IF it is in the signal path it need not be anywhere near 100V... more important would be that it physically fits, and the right size lead spacing is nice too.

http://www.digikey.com/product-searc...acitor&stock=1

Otherwise I agree you could use the 10uF /100V cap.

Last edited by 999999999; 11-24-2012 at 03:43 PM..
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Old 11-24-2012, 04:59 PM   #11
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Here's a pic of the cap.

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Old 11-24-2012, 05:19 PM   #12
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

You could also get two polarized capacitors and connect them together to form a bipolar capacitor.

http://www.digikey.com/product-detai...1968-ND/589709

Tie minus to minus or plus to plus on two of these and you have a ~ 7 uF bipolar capacitor.

Something like this may also work, but don't quote me on it: http://www.digikey.com/product-detai...527-ND/1647808
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Old 11-24-2012, 05:51 PM   #13
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Quote:
Originally Posted by mariushm View Post
You could also get two polarized capacitors and connect them together to form a bipolar capacitor.

http://www.digikey.com/product-detai...1968-ND/589709

Tie minus to minus or plus to plus on two of these and you have a ~ 7 uF bipolar capacitor.

Something like this may also work, but don't quote me on it: http://www.digikey.com/product-detai...527-ND/1647808
Hm, this needs some experimenting. It appears that the capacitors run hot, so the electrolyte in them dries/boils. That film cap might be a good solution (it won't boil). But I am not sure if it would work or not also.
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Old 11-24-2012, 06:58 PM   #14
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I know nothing about this sub's amp, but I am suspecting it is class D and that is a signal coupling cap but in the circuit it sees a much higher switching frequency.

Yes I'd try a film cap there, it won't physically fit but either the leads may be long enough or you could use add-on wires to get it mounted. Some of the parts around it may generate a fair amount of heat, I'd try to isolate it some and maybe put some cement (silicone caulking would suffice) to hold it away from other parts.

It's likely the only reason they didn't use a film cap in the first place was the higher cost of film caps.

I wonder if it would help to mount a little fan inside to keep the electronics cooler, though given the vibrations present it probably ought to be a sleeve bearing fan and not rigidly mounted to the cabinet so it isn't jarred as much.

Last edited by 999999999; 11-24-2012 at 07:08 PM..
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Old 11-24-2012, 07:15 PM   #15
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

That cap is part of the Class D output filter network, http://www.ti.com/lit/an/sloa119a/sloa119a.pdf

http://www.maximintegrated.com/app-n...dex.mvp/id/624

Very common failure and it is cheap for them them to use Lytic non-polar than the expensive and big film cap.
I have JBL PB10/12, I ended up using the Film cap from PARTEXPRESS.
http://www.parts-express.com/term/6.8uf?srch=6.8uf
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Old 11-24-2012, 08:46 PM   #16
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Just installed the new cap.
Watching Predator.
IT'S WORKING AGAIN!! YAAYYYYYY!!

Thanks guys for all your help and support.
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Old 11-25-2012, 06:16 AM   #17
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Quote:
Originally Posted by JCnBoys View Post
Just installed the new cap.
Watching Predator.
IT'S WORKING AGAIN!! YAAYYYYYY!!

Thanks guys for all your help and support.
What cap did you decide on using?

P.S. we always like to see the finished job (pics?)
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Old 11-25-2012, 11:25 AM   #18
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I used the 10uf 100v.
It's all put back together now. It's east enough to take apart, so I'll take some pics and post later.

I will say that when the speaker hits REALLY hard, it crackles.
Maybe I should take out the 10uf and try a 4.7uf?
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Old 11-25-2012, 11:28 AM   #19
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

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Originally Posted by JCnBoys View Post
I used the 10uf 100v.
It's all put back together now. It's east enough to take apart, so I'll take some pics and post later.

I will say that when the speaker hits REALLY hard, it crackles.
Maybe I should take out the 10uf and try a 4.7uf?
It crackles, or is the speaker bottoming out?

If it crackles, then it's a bad solder joint.

If it bottoms out, either the capacitor needs to be smaller (6.8uF), or your playing your dubstep too loud
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Old 11-25-2012, 11:54 AM   #20
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Default Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

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Originally Posted by ben7 View Post
It crackles, or is the speaker bottoming out?

If it crackles, then it's a bad solder joint.

If it bottoms out, either the capacitor needs to be smaller (6.8uF), or your playing your dubstep too loud


I'm pretty sure it's the dubstep (what's that?).
Is that that dance that Popcorn does on the show Moonshiners?

It only "crackles" when it hits really hard. So, I'm assuming it's bottoming out.
But it never hurts to double check the solder joints.

I'll look for a 6.8uf 100v radial NP. If I can't find one I just might try an axial.
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