Infinity PS-12 Powered Subwoofer Fired Amplifier

[ben7]

Originally Posted by JCnBoys

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.

[hardwareguy]

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!)

[budm]

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/

[Beretta6888]

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.

[999999999]

^ 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]

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?

[budm]

Service manual:
http://elektrotanya.com/infinity_ps-.../download.html

I just got PS-10 today.

[Beretta6888]

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]

http://www.parts-express.com/pe/show...umber=020-1429

This one does not fit?
there are two caps, one is 4.7 and another one is 6.8

[hardwareguy]

If the chip cap burns on the solder side of the board, CHECK THE AUX SUPPLIES!

In many cases, the output MOSFETs will survive this insult. Use film caps in place of the bipolar electrolytic caps. (they fit with a little creativity).

[RonAlam]

what type is the chip capacitor? I have the same sub with bad cap and burned out chip capacitor. Any help would be appriciated

[RonAlam]

almost forgot, which side is positive and which is negative on the board? I have no way of telling.