AC30 Wiring Layout

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by TheAmpNerd, Oct 3, 2011.

  1. TheAmpNerd

    TheAmpNerd Member

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    I'll have to post some pics.

    Trying to resurrect an old AC30. Not that old,
    is the SS rectifier one.

    Horrible hum, and pots/parts replaced prior...


    ...I'm trying to sort it all out here.

    For now, this is where I'm at...

    voltages are +-10/20 percent, in spec.

    vib/trem vol and brillant vol effect hum and normal
    volume and playibility.

    thinking channel caps resistors/wiring fault...

    the service manuals that i bought years ago are
    worthless. none show wiring layout...

    any help appreciated.
     
    Last edited: Oct 5, 2011
  2. TheAmpNerd

    TheAmpNerd Member

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    Location:
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    I'm thinking the problem may be with the normal volume pot,
    Center tab thru 220K connects to the 500pf cap at A17
    Right tab connects to .047uf cap on A 26.

    Or

    Is this a pretty standard issue with the AC30? (CD7 is there for fitting purposes, not soldered in.)

    [​IMG]



    And the right side here. (AB40 is there for fitting purposes and not soldered in.)

    [​IMG]
     
    Last edited: Oct 5, 2011
  3. TheAmpNerd

    TheAmpNerd Member

    Messages:
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    Here is the AC30 that I've got and gave up on and recently working on it
    again. These are pics from the late 80s hand wired LTD edition from
    what I can tell.

    Interestingly I found some other pics of one on the net and it is slightly different than the with the GZ34.

    To note these are the specific differences that I've found and they
    may be part of the problem on my amp. But it also looks like they
    used this in production, so I still don't know if I got it right.

    Nomenclature I've useful is the row closest to the pots is A, with the
    closest to the input jacks is 1. So the Negative side of 25uf/25v cap is A1
    while the positive side is B1.

    Exceptions that I've identified are as follows:

    Normal pot Center Tab connects with 220K resistor to A17, ground.
    This is the place between the 470pf and .1uf caps.

    Brilliant pot 100pf cap connects to left tab and center tab.
    Different then center tab and right tab.

    Bass pot, right tab only connected to resistor to cent tab, no ground connection.

    Cut pot, right tab as shown, no center tab jumper, end point as shown.
    Cut pot, center tab is center tab, end point as shown.

    So I don't know what effect these changes have on the amp
    other than this silicon rectified amp sounds different than GZ34
    tube rectified amps.

    Here are some pics of what I have and I found this link on the net.

    http://web.comhem.se/~u70623527/Vox%20AC30,%201960%20bass%20and%20treble.jpg

    Here is the link of the alternative pot wiring and the guy seems
    to blame it on the silicon diodes and I wonder if he realizes if the
    the wiring is different on the pots to the main board.

    http://www.chambonino.com/work/vox/vox1.html

    Question is does this constitute the top boost?
     
  4. TheAmpNerd

    TheAmpNerd Member

    Messages:
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    Joined:
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    I should have realized this sooner.

    The replaced pot, the TremVol pot was damaged.

    Don't know if the unit came that way or damaged in shipping
    who knows. But when I got the amp it was in there and always
    was causing problems, unbeknownst to me.

    So a little bit of clean and removal along with the normal
    channel testing to see where it best fits in as located or
    where it typically is found through the 220K resistor tied
    in over at A36.

    Either way, the Norm and Brilliant channels are tied together.

    Yea! the replaced TremVib pot.

    [​IMG]
     

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