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A few questions for Schack owners

Discussion in 'Pickups & Electronics [BG]' started by Le Basseur, Apr 25, 2005.

  1. Le Basseur

    Le Basseur

    Mar 26, 2002
    Hi all,
    I just got on repair a Schack axe.Unfortunately,it's impossible to identify precisely what model is,but I found a description wich gets very close:
    (...OK,the guy is a little euphoric,don't flame him...)
    The bass I got is very similar as described (bolt-on,4 strings,Gotoh tuners,fixed 3-band electronics) but is fretless (ebony fingerboard).There's no logo on the headstock.
    The problem is that a previous owner messed up with the preamp and wiring...the bass isn't behaving quite normally,so I urge the owner(s) of a similar instrument to help me getting the right picture of what's happening here.
    My questions are:
    1.This bass came with the PU's (Basstec JB's) wired in anti-phase.Is this normal?
    I tried to wire the PU's in phase but I got a weak signal when the blend pot was in the middle;the response went normal on both pot's ends...but this means only a PU at a time...
    2.I have 3 dip switches on the PCB,as you can see they're each covered with a thin transparent green plastic film...how do they work (wich does what)?
    3.I have a grey wire banging inside (it's wired on the PCB but it doesn't go nowhere on the pots...looks like it's been cut off).If you look at the posted pic of the PCB,it's the 6th wire from right to left,between the violet and the white one.Where's the other soldering point of this grey wire?
    I tried to write to Schack but I got no answer so far...it might be simpler to manage to get this working by getting some help from you,guys.
    Thank you alot,
    Le Basseur
  2. Le Basseur

    Le Basseur

    Mar 26, 2002
    The control cavity and the PCB:
  3. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    It is quite common to wire p-ups out of phase for hum-cancelling.
    By reversing that now your p-ups are fighting each other in the blend middle position
  4. ingo62


    Mar 15, 2005
    Emden, Germany
    I sold my Schack several years ago, but still have the DIP-parameters as a word file :)
    "Empfehlung" means "recommended".


    0000=100 Hz Empfehlung
    0010=110 Hz
    0100=120 Hz
    1100=120 Hz
    1000=130 Hz
    0001=135 Hz
    0110=140 Hz
    0011=140 Hz
    1010=150 Hz Empfehlung
    1001=160 Hz
    0101=220 Hz Empfehlung
    1101=230 Hz
    1011=250 Hz
    0111=280 Hz
    1111=300 Hz Empfehlung

    0010=2,0 kHz
    0000=2,5 kHz Empfehlung
    0001=2,5 kHz
    0011=2,5 kHz
    1001=3,5 kHz
    1011=3,5 kHz
    1000=4,0 kHz
    1010=4,0 kHz Empfehlung
    0101=6,5 kHz Empfehlung
    0110=7,0 kHz
    1101=7,0 kHz
    0111=7,0 kHz
    0100=7,5 kHz
    1110=7,5 kHz
    1100=8,0 kHz
    1111=8,0 kHz Empfehlung

    Mitten (Q=Flankensteilheit):
    0000=500 Hz, Q=1 Empfehlung
    1000=550 Hz, Q=0,6
    0100=600 Hz, Q=0,45
    0010=600 Hz, Q=1,9
    1100=650 Hz, Q=0,35
    0001=700 Hz, Q=3,2
    1010=800 Hz, Q=1 Empfehlung
    0110=800 Hz, Q=0,75
    0011=850 Hz, Q=-6 ??
    1001=850 Hz, Q=1,5
    1110=900 Hz. Q=0,6
    1101=1 kHz, Q=0.75
    1011=1 kHz, Q=2
    0111=1,1 kHz, Q=13
    0101=1,2 kHz, Q=1 Empfehlung
    1111=1,5 kHz, Q=1 Empfehlung

    Greets from Germany
  5. Le Basseur

    Le Basseur

    Mar 26, 2002
    Thanks Frank for your reply!
    Yes,I'm well aware about out-of-phase hum cancellation technique regarding PU's.I should post my question somewhat differently,like "is this normal ON THIS BASS?".
    Still,the question remains the same...I'm not concerned at all because of the hum because I intend to do a complete restoration of this bass,including a proper copper-foil or graphite paint on all the cavities...this is why I'd like to know how the original wiring looked like.
    Thanks and regards,
    Le Basseur
  6. Le Basseur

    Le Basseur

    Mar 26, 2002
    Hi Ingo,
    Thanks a lot for these parametres!
    I wouldn't expect more! :hyper:
    ...at least,now I know what's going on with those dips...
    One more question:can you remember wich switch group does what?(see my photo....what's the switch group for bass,what's for mids,what's for highs)?
    ...of course,I could establish that by switching each of it and listen the results,but,if you recall something about it,I'd spare alot of time! :bag:
    Thank you! :hyper: :hyper: :hyper:
  7. ingo62


    Mar 15, 2005
    Emden, Germany
    Hi Le Basseur

    as far as I remember:

    mid = next to the small trimpot for volume
    bass = under the mid-DIP
    treble= right from the other ones

    I hope I remembered well :)

  8. Le Basseur

    Le Basseur

    Mar 26, 2002
    Yes Ingo,you remembered corectly! :hyper:
    I couldn't wait the replay to my question and today I dug the dips' functions/freqs according to your parameters' list.
    I managed to get some awesome tones from this little beast...who'd thought?The onboard preamp is a surprising thing for a electronics piece from that time (the bass I have is at least 10 years old,maybe even more).
    I found out that what I presumed in the first place (the axe is REALLY breathing) became more evident with the appropriate preamp's tweak.Since this bass is on sale,I'm seriously thinking about keeping it! :bassist:
    ...now,only if I could find a proper string set for it...it came with some dead Rotosound 77's and I put a ****ty (even if new...) set of Warwick "Black Labels" wich I don't like very much either (they're too "nasal",no matter of what I tried with the pre).
    Any hint?
    Thanks again and best regards,
    Le Basseur
  9. ingo62


    Mar 15, 2005
    Emden, Germany
    Hi Le Basseur,
    I used Ken Smith stainless steels for my Schack, not to stiff, because it was a 36"-Scale. 40-125 I think.
    Nowadays I prefer nickels, but for that "slap monster"
    (I has a headless "carbon V") stainless was just right :bassist:

  10. Le Basseur

    Le Basseur

    Mar 26, 2002
    Hi Ingo,my Schack is a 34'' bolt-on fretless,therefore a totally different story.
    ...but,thanks anyway for your reply!
    Le Basseur
  11. Hi as a further question,

    When you change the dip switches how do you know which way is on or off.

    My Schack pre has written on each of the 3 banks of switches the following.

    ON DIP
    4 switches

    I cannot work out if a dip is at '0' when moved up to the 'on DIP' side or down towards the '1234'

    Many thanks

  12. Le Basseur

    Le Basseur

    Mar 26, 2002
    Hi Matthew,
    Here's a pic of my pre.Maybe resembles yours,maybe not...but,anyway,take at the look at the dip switches.
    They're marked "OFF" on the lower side and "1234" on the upper side,meaning that the "ON" position for each switch is toward upper side,to the corresponding number/frequency (as given by Ingo).
    Even if your dips don't look like mine,from what you described it's obvious that a switch is "ON" when it's moved up to "on DIP".To be more convincing,try the following:
    1.Pull out the jack from your bass
    2.Pull out the batteries of the preamp
    3.Use an Ohmmeter and measure the corresponding dip's pins (underside of the PCB),just to be sure if I said the right thing.
  13. Le Basseur

    Thanks for your post. Now that you say it, it is obvious, but thanks anyway for replying and helping out a very slow person!

  14. Le Basseur

    Le Basseur

    Mar 26, 2002
    Ouch...looks like I managed to offend you...sorry if that "obvious" sounded offensive to you,I didn't mean anything in this direction.After all,English isn't my native language and it happens sometimes to write down good,positive or normal things in a wrong manner.
    Once again,I appologise!
    Best regards,
    Le B
  15. Le Basseur

    Do not worry, you did not offend me at all. I am a little slow due to the medication that I have been taking for the past year. What you said was totally correct and as soon as you pointed it out it made sense to me. So thank you.



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