Infinity PS-12 Powered Subwoofer Fired Amplifier

[Beretta6888]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Anyone find a good capacitor to buy online, I can't find a cap with the right specs from the previous link to parts express.

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Service manual:


I just got PS-10 today.

[Beretta6888]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Okay thanks, just making sure there isn't anything else like one of those small diodes or resistors located where the burn is, I guess the board just shorted there then?

[999999999]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

^ See the picture linked originally, and below, there is nothing directly under the capacitor but between the solder pads for it and the outermost screw securing the heatsink, there are a pair of diodes and resistors on the back of the board.

Also moving away from the heatsink, left in the picture towards the edge of the board, there's one cap, then an inductor, then a 2nd cap on top of the board. That second cap does have a chips capacitor on the back of the board situated between it and the inductor.

[Beretta6888]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

I have the same problem with the capacitor but my circuit board has burned much worse than the first posts. Is there just the one capacitor or is there a very small resistor or cap on the bottom of the circuit board next to where the faulty cap is connected? Also can anyone give a link of where to find the capacitor needed, the link in an earlier post doesn't come up with the same specs.

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Yeah, the JBL uses that crappy ClassD module in PB-10/12. I mod a couple of them with free sample power amp IC from National/TI instead.
http://s807.photobucket.com/albums/y...20PB-12%20mod/

[hardwareguy]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

If this amp dies again, make sure the muting and modulator power supplies are up.

The large power resistors feeding the small regs off of the main rails are undersized on a few of these. JBL/Harman specifies a 3W and a 5W resistor but some units have a 1W and a 3W respectively. These overheat the board leading to some SMD transistors nearby to fail outright or become leaky.

The traces will be visibly discolored and the solder joints at the resistors will be in poor condition.

The service manual for the JBL-E250 and PB12 covers this amplifier. You have the Revision 2 board. (rev. 1 uses a very nasty hybrid module and isnt really worth fixing!)

[ben7]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

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.

It could be that it needs to be vibrated very hard to make the [possible] bad solder joint disconnect/reconnect.

When a speaker is bottoming out, it will sound like a muffled 'brrrrr' 'brrrrrr'; a bad solder joint causing an interruption in a signal path would make the speaker produce a sharp crack or pop sound.

[JCnBoys]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

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.

[ben7]

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?

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

[JCnBoys]

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?

[ben7]

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.

What cap did you decide on using?

P.S. we always like to see the finished job (pics?)

[JCnBoys]

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.

[budm]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

That cap is part of the Class D output filter network, https://cdn.badcaps-static.com/pdfs/...974574fbd7.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

[999999999]

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.

[ben7]

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

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.

[mariushm]

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

[JCnBoys]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

Here's a pic of the cap.

[999999999]

Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

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.

[Th3_uN1Qu3]

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.