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Thread: B-401 Electronics

  1. #1

    B-401 Electronics

    Has anybody got a schematic for the electronics in a B-401?
    I'm trying to fix one at the minute and its difficult without the circuit diagram.
    Alternatively, if I reverse engineer the schematic from the board would anyone be interested in me posting it here?

    Also - I'm new here. Hello everyone.

  2. #2
    Senior Member SFIV1967's Avatar
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    Welcome to LTG! Can't remember schematics for the B-40x series, but maybe somebody here has that info. Stay tuned.
    Ralf

  3. #3
    Hello from Finlad


    Welcome to LTG !!!

    A quick look via Google reveals, that it has series-parallel switch - that is easy. Check the switch.
    Then there is active B+T circuit, which probably is done with OP-amp and fairly straightforward - at least to anybody comfortable with analog electronics.

    No - I do not have the circuit diagram - but I would replace the IC - check all caps and check for bad solder joints.

    While you do not give more info of what the problem is - I'll stop here and "listen"

    Good luck
    First good guitar - GUILD Duane Eddy 400 - I was 3rd owner - still regret letting it go 25 years ago - used to have Artist Award and Starfire - no regrets here.
    Present guitars - all bought new - F50R 1975 - F512 1977 - F212CSB 1979 - OM-240CE 2018 - Schecter Startocaster
    Bought secondhand - B30SB fretless - RED Songbird - White Songbird - S-60D - D-125 - Gibson 3/4-size acoustic 1957 - Carmelo Gonzales nylon string - old Levin Lute

  4. #4
    Senior Member SFIV1967's Avatar
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    Quote Originally Posted by Nuuska View Post
    Then there is active B+T circuit, which probably is done with OP-amp
    Correct, here's a picture of a B-401. The PCB is the same as used in the B-402. The Op-am (I asume it's a Texas Instruments TL062CP http://www.ti.com/lit/gpn/tl064) seems to be in a socket, so replacing would be easy if there is an issue with it.



    The only schematics I found for basses using the TL062CP are for the Musicman Stingray bass:
    http://static.musicforums.ru/agora/f...ngraypre01.jpg
    http://static.musicforums.ru/agora/f..._schematic.jpg

    Ralf
    Last edited by SFIV1967; 11-04-2019 at 10:48 AM.

  5. #5
    And TLO62 can be replaced with myriad of other OP:s
    TLO72 - TLO82 - or just about any Dual-Op-Amp with same pinout.

    Quick Google gives this - looks promising - I did not wade through it - https://www.youtube.com/watch?v=6xRAAWZeC9Q
    First good guitar - GUILD Duane Eddy 400 - I was 3rd owner - still regret letting it go 25 years ago - used to have Artist Award and Starfire - no regrets here.
    Present guitars - all bought new - F50R 1975 - F512 1977 - F212CSB 1979 - OM-240CE 2018 - Schecter Startocaster
    Bought secondhand - B30SB fretless - RED Songbird - White Songbird - S-60D - D-125 - Gibson 3/4-size acoustic 1957 - Carmelo Gonzales nylon string - old Levin Lute

  6. #6
    Hi - thanks for all your replies.
    The TL062 is the op-amp of choice for battery powered applications because its optimised for low power.
    In my case, the op-amp is fine. The problem was neither of the tone controls worked and there was no output from the bass with no battery fitted - regadless of the switch position.
    I assumed, therefore, that there was something wrong with the active circuitry.
    The actual problem was, however, that there was a bad connection on the output jack meaning that the pickup return wire was only connected to the output jack via the battery.
    With a battery fitted, it only worked with the switch in the passive position - so neither of the tone controls worked.
    The schematic is still a work in progress, and I need to verify it, but the first draft is complete so I'll post it here tomorrow.

  7. #7
    Senior Member adorshki's Avatar
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    Quote Originally Posted by richw1968 View Post
    Hi - thanks for all your replies.
    The TL062 is the op-amp of choice for battery powered applications because its optimised for low power.
    In my case, the op-amp is fine. The problem was neither of the tone controls worked and there was no output from the bass with no battery fitted - regadless of the switch position.
    I assumed, therefore, that there was something wrong with the active circuitry.
    The actual problem was, however, that there was a bad connection on the output jack meaning that the pickup return wire was only connected to the output jack via the battery.
    With a battery fitted, it only worked with the switch in the passive position - so neither of the tone controls worked.
    The schematic is still a work in progress, and I need to verify it, but the first draft is complete so I'll post it here tomorrow.
    Wonderful trouble-shooting summary.
    I'm not even an "electric guy", but I'm sure I speak for at least several folks here in saying "You, sir are a fine contributing citizen and many thanks!"
    And btw, "Welcome Aboard!"
    Al
    "Time May Change the Technique of Music But Never Its Mission " - Rachmaninoff
    My 1st Guild: '96 Westerly D25NT "Hally" (10-31-96 stamped on heelblock)
    #2: '01 Westerly F65ce "Blondie"
    #3: '03 Corona D40e Richie Havens "Richie"
    All bought new!

  8. #8
    Senior Member SFIV1967's Avatar
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    I am really surprised no schematics are available for the B-401 and B-402 yet.

    Ralf

  9. #9
    OK - here is the first draft of schematic.
    This still needs verification and I haven't yet worked out how it all works.
    Please feel free to make any comments at all - if anyone wants anything changed or updated, please let me know.
    The jpeg shows the component references I have used in the schematic.
    I promise that R14 is definitely there - hiding under the green wire.

    https://app.box.com/s/w0t7qhy98e8hc2kx1fco228ruijfi3fj

    https://app.box.com/s/yy507nd699f8qbcq1rqb7nrij4ecz2wi

    Thanks also to everyone for your kind & helpful comments.
    Last edited by richw1968; 11-08-2019 at 09:19 AM. Reason: Fixed broken links

  10. #10
    Senior Member adorshki's Avatar
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    Quote Originally Posted by richw1968 View Post
    OK - here is the first draft of schematic.
    This still needs verification and I haven't yet worked out how it all works.
    Please feel free to make any comments at all - if anyone wants anything changed or updated, please let me know.
    The jpeg shows the component references I have used in the schematic.
    I promise that R14 is definitely there - hiding under the green wire.



    https://app.box.com/s/yy507nd699f8qbcq1rqb7nrij4ecz2wi

    Thanks also to everyone for your kind & helpful comments.
    Link works but file type isn't compatible with the image linking function here (or at least, not under my browser), in case you were wondering.

    Al
    "Time May Change the Technique of Music But Never Its Mission " - Rachmaninoff
    My 1st Guild: '96 Westerly D25NT "Hally" (10-31-96 stamped on heelblock)
    #2: '01 Westerly F65ce "Blondie"
    #3: '03 Corona D40e Richie Havens "Richie"
    All bought new!

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