Problem with SC2.2 V4

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  • #15347
    AvatarConen
    Participant

    Hello Ted,

    I just bought a second hand Joemeek sc2.2 V4 (tested on 22.01.02)

    when the compressor is in baypass the sound flows perfect ,

    but when the compressor is activated, the stereo audio program becomes mono .

    any suggestions?

    Thanks

    Carlo Conen

    Sardinia ITALY

    #16025
    Ted FletcherTed Fletcher
    Keymaster

    This is actually a very interesting question….. It’s only very recently I discovered that in a few SC2 V2.2 V4 there was a problem with the design of the output stage.

    I can’t recall how it happened; and we knew nothing about it at the time.

    The SC2.2 was the first stereo compressor that used the ‘sum and difference’ routing….. the L and R signals are converted to Sum and Difference before compression, then at the output stage they are re-converted to L and R. The problem is that the output stage does not behave correctly and provides a very near ‘mono’ output….. BUT it only does this if the output is being used as a balanced line!

    I would ask that you try using the compressor in ‘unbalanced’ mode (that is, link pins 3 and 1 in the output XLR connectors) and there is a chance that the problem will be solved.

    Normally I can offer to correct any faults in any equipment that was designed by me originally, but in this case, it was an original problem caused by a mistake somewhere in the manufacturing process. I have only ever seen one of these faults, and that one worked perfectly in unbalanced mode.

    In case anyone needs the circuit diagram of this model, please email me at ted@tfpro.com. :(

    #16026
    AvatarConen
    Participant

    I’ll try your suggestion

    thanks

    #16027
    AvatarConen
    Participant

    Hi Ted,

    I tried to use an unbalanced cable to the output, but compressor still returns a mono signal.

    do you think I can send to you the unit for repair ? can I write to you in private for repair cost ?

    regards

    Carlo Conen

    #16028
    Ted FletcherTed Fletcher
    Keymaster

    I’m really sorry to hear that you still have a ‘mono’ problem.

    Yes, please send me the unit and I will fix it.

    As an update for others reading this, I do ‘service’ older Alice, JoeMeek and TFPRO equipment of my design as an ongoing help to users. In most cases I charge a fixed fee of UK£50 plus the cost of return and cost of any expensive components that might be needed. 8-)

    #16029
    AvatarConen
    Participant

    shipping to ?

    5 Bay Court

    24 The Fairway,

    Aldwick Bay Estate,

    Bognor Regis, PO21 4HD

    It’s correct ? 😳

    #16030
    Ted FletcherTed Fletcher
    Keymaster

    That’s correct. 8-)

    As soon as I have the SC2.2 on the bench I will publish the result here….. just in case there are any others like it.

    #16031
    AvatarConen
    Participant

    I Shipped by courier today :D

    #16032
    Ted FletcherTed Fletcher
    Keymaster

    I did say that I would post the results of this one on the forum…..

    Exactly as ‘Conen’ says, the compressor had a mind of its own and produced a mono signal whatever went into it. As well as that, the compressor seemed sluggish and not working properly.

    The first fault was a dry joint on the PC board in the ‘difference’ channel, this locked the amplifiers into a ‘mono’ mode.

    The second fault was a failed transistor in the LED drive circuit to the optical compressor, this allowed a meter indication of compression…. but it hardly did anything.

    So with the PC board fixed and the drive transistor replaced, it’s back to working as good as new! :D

    #16033
    AvatarConen
    Participant

    :D I’m very happy

    I can’t wait to to having it in the studio

    thanks Ted.

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