seeking Fender reverb unit (6G15) knowledge

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by jawjatek, May 22, 2008.

  1. jawjatek

    jawjatek Member

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    I have a vintage "65 Fender reverb unit (6G15) I snagged that I am using at gigs. I went over it pretty good when I first got it used, but I have some questions about the actual reverb pan inside, and how it is mounted. I've been working on amps a long time but never worked on one of these until I got one for myself. The unit works well but gets too surfy much past 3 on the mix (like most of 'em I've played). The bare pan is mounted to the front board of the unit (not on the bottom in a vinyl bag like a combo) and suspended by 4 springs that are attached to the 4 front board mounting screws. There is a locking bar you can use to clamp down the pan during transport. All stock as far as I can tell, except...

    When I got the unit it had two thick pieces of foam glued to the front board under the reverb pan, between the pan and the board. Is this stock? Seemed to dampen the pan quite a bit and didn't look right, so out they came. Also, the springs inside the pan (long springs) seem to rattle excessively during transport even with the locking bar engaged. So I guess the springs inside are getting floppy with age. The 4 pan suspension springs are good (had to re-attach one) and the pan does not move around when the bar is locked. Also, there is no cardboard cover on the pan like there is on a combo pan. I'd hate to replace this Gibbs pan with a reissue, and I don't think the reissue is the same pan anyway, so I want to make sure things are correct.

    So: any advice for fixing up the mechanics of the 6G15 reverb pan? How exactly did these come from the factory with regard to pan mounting? Is the pan supposed to have a carboard lid on it like the combos? Any foam supposed to be in there?

    I would greatly appreciate any info anyone can provide if thay have a vintage unit they can look at. I do have the old Gerald Weber book and there is a little info on the 6G15 there, but not much about the pan. TIA

    :JAM Joe
     
  2. mark norwine

    mark norwine Member

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    The foam is supposed to press against the springs when the lock bar is engaged, and not touch the springs when not engaged.

    There's no cardboard (as that would defeat the purpose of the foam / lock system)

    EDIT...I should add: One thing that can happen....as the foam gets old & icky and starts to break down [as all foam does], little sticky bits can "press into" the springs, killing the reverb effect. The foam serves it's purpose {dampening during transit}, but should be changed after a while so that it doens't break down & gunk up the springs

    The pan is a typical 4AB3C1B

    mn
     
  3. BenH

    BenH Member

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    As to where the pan is mounted, The letter on the end of the cans part number will tell you this. For Accutronic pans, mounting should be as follows;
    Last letter - A - Horizotal mount, open side up.
    - B - Horizotal mount, open side down.
    - C - Vertical mount, connectors up.
    - D - Vertical mount, connectors down.
    - E - On end , input up.
    - F - On end , input down.
    All of the mounting springs inside the thing are worked out to have the reverb springs hanging in the right position when the unit is mounted correctly.
    Ben.
     
  4. jawjatek

    jawjatek Member

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    I guess I should replace the foam then. It was kind of sticky. I guess I'll use some 3M 77 spray adhesive to glue some back on.

    I am a bit confused about the accutronics tech info. According to the Fender Service manual, the reissue unit uses 4AB3C1C, but the connectors are down, so it seems 4AB3C1D should be used. ??? Are the connectors supposed to be pointed up on the pan? Seems hard to get to...
     
  5. mark norwine

    mark norwine Member

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    "Back in the day", Fender used the same pan for everything. I'm not altogether sure the mounting orientation really matters all that much.
     
  6. jawjatek

    jawjatek Member

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    My mistake, the connectors are on top, so 4AB3C1C is indeed the pan used in the reissues.

    Now I just need a pic of the foam in a vintage or reissue 6G15 unit so I can duplicate it. Anyone take theirs apart and have pics??
     
  7. Wakarusa

    Wakarusa Member

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    Small world.. I've got a '65 6G15. I'll have to dig it out to get a look at the foam tho' (maybe later today?).

    The original pan was definitely a 4AB3C1B. Funny thing is that the only difference in pans with a different mounting orientation code is where the spring/transducer unit is suspended in the tank frame (if you look, there are a series of holes where the wee mounting springs can go. The orientation/mounting code is just tied to which set of holes they use to suspend the guts).

    Something you might want to try is replacing the original pan with a 9AB3C1B (the six spring version instead of the stock 4 spring version). In old Fender combos the 6-spring is typically over the top, but in a 6G15 you have a dwell control. All the difference in the world.
     
  8. Galapogos17

    Galapogos17 Gold Supporting Member

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    Could someone post a photo of the foam? I'm replacing the foam in my unit and I'm trying to figure out if the center should be lower than the sides.
     
  9. WaltC

    WaltC Member

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    Nope. They're just foam blocks glued to the "front" panel. The trick is to get them the right "depth" so that they press gently on the springs when the lock is engaged and don't touch at all when it's released. Don't have one to hand currently but the older ones I've seen and worked on were about 2" square and about 1 & 1/2 " thick, and there were two of them dividing the tank roughly in thirds. Make sure you don't locate them where they will press on the transducers.
     
  10. Galapogos17

    Galapogos17 Gold Supporting Member

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    Ok, I think the foam I used is about 1'', maybe that's not the problem then. Thanks for the input.
     

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