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Thread: 4344, 4345, 4355

  1. #1
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    Post 4344, 4345, 4355

    As per a member's request -

    The following capacitors in the JBL Model 5234A can benefit from 0.01uF poly film and foil bypass capacitors:

    C1, C2, C3, C4, C5, C6
    C101, C102, C103, C104, C104, C106

    The schematic is located in the back of the manual which can be downloaded here:

    http://www.jblproservice.com/pdf/Vin...A%20manual.pdf

    Here is the voltage drive of the 18dB/octave 51-5145 crossover card designed to be used for the 4344, 4345, and 4355 Studio Monitors. Also included is the voltage drive of the 12dB/octave 52-5140 card designed for the 4343 and 4350 Studio Monitors. The 51-5145 is ~ 3 dB down at ~ 290 Hz and the 52-5140 is ~ 4 dB down at ~ 255 Hz:
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    Last edited by 4313B; 07-13-2003 at 08:51 AM.

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    Post Re: 4344, 4345, 4355

    Once biamplification has been implemented, switching the remaining portion of the passive networks to charge coupled capacitor technology isn't nearly such a daunting task from a monetary standpoint. As always, I don't advocate extensive modifications to the stock networks. Building new, bi-amp only, passive networks for the 4344 and 4345 (in the same spirit as the bi-amp only 4355) would be my recommendation.
    Last edited by 4313B; 07-13-2003 at 12:18 AM.

  3. #3
    Senior Señor boputnam's Avatar
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    Nice!

    Thanks, Giskard!

    That clever listing of the involved caps is easier than trying to draft the little buggers onto the schematic!
    bo

    "Indeed, not!!"

  4. #4
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    Yeah, I started to go that route and then decided the schematic was simply too large and lacked the necessary resolution in one shot.

    The 5234A circuit board is plainly labeled so finding the capacitors is quite easy. The 0.01uF poly film and foil bypass caps are physically the same size as the 100 uF electrolytics !!! so you can imagine what's going on here...

  5. #5
    Senior Señor boputnam's Avatar
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    Ha!

    So, might you have any pictures laying about that represent a bypass cap in position, so us novies at this can get a better handle on the physical positioning of it all?

    Pretty please?

    bo

    "Indeed, not!!"

  6. #6
    Senior Member Don C's Avatar
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    This is what mine look like. This is not DIY, this is how JBL did it.

  7. #7
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    And here's a custom 3113B. I'll post a 5234A picture later today.
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    Last edited by 4313B; 07-14-2003 at 05:00 AM.

  8. #8
    Senior Señor boputnam's Avatar
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    Wow, nice clean job. Something to admire.

    And, I gotta say, that my 3113B's look NOTHING like that. That's a beauty. Those inductors (and caps, too...) are cherry better than than the original. Dang it! I see yet another project coming.

    If only you'd do this commercially...

    Hey DonC - which network is that?

    Thanks for the pics - very helpful.
    Last edited by boputnam; 07-14-2003 at 06:26 AM.
    bo

    "Indeed, not!!"

  9. #9
    Senior Member Don C's Avatar
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    It is N240Ti

  10. #10
    Senior Señor boputnam's Avatar
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    here's a custom 3113B

    Giskard...

    I'm thinking part of why this 3113B looks so dang clean (irrespective of your enviable soldering (and layout) skills... ) is that the signal paths not to/from the Lpad before leaving the network, but exits the network, goes through the Lpad and then goes directly to the transducers - correct? You have commented on the merits of that, before.

    You inspire me to redo my 3113B's nearly entirely before/during the bypass cap episode. Is there any rudimentary schematic that you made-up for your effort, that helped with the layout? I'm thinking ahead to the 5234A's too...
    bo

    "Indeed, not!!"

  11. #11
    PSS AUDIO
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    Originally posted by Don C
    This is what mine look like. This is not DIY, this is how JBL did it.
    May I give you an advice?

    Remove those two electrolytic non polarized capacitor and replace them with whatever you want (polypropylene is the best) but change them and you will hear a new speaker!

  12. #12
    Senior Member Don C's Avatar
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    Originally posted by PSS AUDIO
    May I give you an advice?
    Advice is always welcome, Thanks!

  13. #13
    PSS AUDIO
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    Originally posted by Giskard
    And here's a custom 3113B. I'll post a 5234A picture later today.
    May I give you an advice too?

    Remove the screw placed to fix the coil as it changes its value.

  14. #14
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    Thanks Yuri but it's inert
    I checked that out twentysome years ago when JBL went from using 2.5 mH iron cores in the early runs of L96's to 2.5 mH air cores in the later runs of L96's and started running bolts through the coils
    Last edited by 4313B; 07-16-2003 at 06:52 AM.

  15. #15
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    Here's an AudioCap 0.01uF poly and how it should go across the electrolytics. The alligator clips are used as heatsinks while soldering. These are too large and one should use smaller clips, or hemostats, but they are all I had close at hand for the photo.
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    Last edited by 4313B; 07-14-2003 at 05:20 PM.

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