JBL PB12 fixes?

Discussion in 'Speakers' started by chuckg, Jun 30, 2005.

  1. chuckg

    chuckg Supporting Actor

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    Hello! I'm sure somebody will suggest I do a search for this, but I have and can't find what I'm looking for! (silly me)

    Does anyone know precisely what fix has been made on JBL PB12 subs? I hear there are a couple of capacitors that go bad, and cause odd noises. My sub turns on and off demonically. I wouldn't mind removing the auto on/off feature completely, or rigging it to operate with the 12v trigger from my Rcvr. simple enough once you know how, right?

    If I had a circuit diagram, I'm sure I could puzzle out how to hotrod the thing myself. If I get tired of looking for the answer, maybe I'll have to do some actual work and trace it out for us all!


    BTW - it sure is confusing to find "PB12" used for another sub -- one that is likely to be much better than the JBL!
     
  2. John Garcia

    John Garcia Executive Producer

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    How old is it? If it's not that old, have them replace the amp under warranty. They know how to fix it, but I don't think they are going to be likely to tell you what it is so you can do it yourself (for legal reasons, I'm sure).
     
  3. ColinM

    ColinM Cinematographer

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    You could just leave it on 24/7.

    Otherwise, I'd find an aftermarket plate amp that'd fit, with some kind of EQ as well since there's likely some built into the JBL.

    Later on if you DIY, you can harvest the amp.
     
  4. chuckg

    chuckg Supporting Actor

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    The sub is 4 yrs old, so the warranty is gone. I can't just leave it on: the auto on/off turns on and off continuously. thumpathumpathumpa all day and night? No thanks!

    If I can defeat the auto on/off, then I'll use the built-in amp. If not, I'll keep using a 200 watt Yamaha pro audio amp which is now sitting on top the sub.

    Looks like I'll be doing some sleuthing over the holidays!
     
  5. JustenH

    JustenH Auditioning

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    Ya i had problem with noise it was repaired under warranty the first time.Then it failed again so i called them because it was out of warranty they dont make the module on power board for price of part they sent me a new sub new one is different.The capacitors where replaced so i tried to change them again very hard to find they are 2200uf x100v do know where u can get them about 12.00 each.but i think my module is also bad and it sealed so no way to test iti have parts if u need them.
     
  6. John Garcia

    John Garcia Executive Producer

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    I'd say it's a good excuse to buy a new and better sub...
     
  7. chuckg

    chuckg Supporting Actor

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    Well, I'd like to buy a new and better sub, but just spent my "allowance" on a new receiver. This sub works fine with a different amp - I watched "Flight of the Pheonix" (new version) last night. I kept cranking up the output on my spare amp, listening for touble with the sub driver. During the sandstorm/flight sequence I had sliding doors shaking and odd household items buzzing and rattling with no noticeable problems in the sub.

    I just want to fix the plate amp for gits and shiggles.





    "what's with all these negative waves?" Oddball in Kelly's Heroes.
     
  8. Marc LaPalme

    Marc LaPalme Agent

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    i've had the same amp for 2.5 years with extensive use. runs like new. all i do is turn the sub on with the switch and turn it off once i'm done.

    simple as that.
     
  9. chuckg

    chuckg Supporting Actor

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    Well, I have my coveted answer. Warning: this link is not for the faint of soldering gun:

    http://www.diyaudio.com/forums/showt...threadid=48627


    There are 23 pages of back-and-forth between serious electrical engineer type dudes, and they have fixed a few of our lovely PB12s. If mine is PCB ver 7.2, it might be easy to fix. If not, it might be easy to use as a door stop. i suppose I should be lucky it ran for four years!

    It just seems so vile to use a Yamaha PC1002 to run a sub....but it really does kick butt, better than when new (and possibly already the plate amp was broken)
     
  10. Marc LaPalme

    Marc LaPalme Agent

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    i just read through about 50% of those pages...

    wow.

    makes ya want to becomes an electrical engineer just for the sheer hell of it.

    and building crossovers of course [​IMG]

    so.... it looks like they did in fact fixed some o the subs but some still blew. they are only replacing blown parts and not changing the design of a badly thought out board.

    i think... when my sub does in fact go... i'm gonna pull the driver, perhaps find another 2-3, (lots of blown pb12s!) and put them in two good 2ohm amps with two solid cabinets.

    booya.

    after all... the driver is the only decent part in this sub anyways!
     

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