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Thread: Anybody have a schematic of Radial Tonebone Plexitube?

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    Anybody have a schematic of Radial Tonebone Plexitube?

    I have this stompbox and the sound in the red channel fades and keep at low level after few minutes of use.
    I already changed the 12AX7 tube and the 2 DPDT switches and the issue remains!!
    Forgive my english, because I am from another country.

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    Senior Member mozwell's Avatar
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    Not sure if these are the ones you want, These are from Dirk Hendriks site.

    Check power supply levels & also check for electrolytic caps that may be leaky.
    Check solder joints & touch up any ones that look "poor quality"
    Attached Files Attached Files

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    mozwell

    Thanks so much for your reply.
    I really need the Plexitube schematic, but both that you posted will be useful anyway!!
    Thanks again!!

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    Senior Member Guitarist's Avatar
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    Man, those tube are hardly doing anything! I thought those were tube-based preamps. I also notice how complicated they look, some some women I try and avoid...

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    Incorrect. Stop thinking in amplification stages.
    What you say here is almost the standard remark made when one sees the tube in this configuration. But keep in mind the low voltage at which the tube is uses causes it to have rather limited "interest" in the hard clipped signal that's being fed into it. That means the signal is being "filtered" with a tube characterististic.

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    Old Timer J M Fahey's Avatar
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    That means the signal is being "filtered" with a tube characteristic.
    I'd *love* to understand what that means ... beyond the Mojo appeal, of course.
    The killer sounds we all love, and think about when talking about "tube sounds", such as in zillions of Fenders, Marshalls, Ampegs, Vox, etc., come from tubes amplifying, eventually clipping, fed with their *working* voltages, say, 160 V to 350V.
    In fact, "doing their thing".
    I fail to see or hear the "tube effect" of a cathode follower.
    In this case, being so starved, it *might* clip signals behaving as some cranky diode, yet compressing *nothing*.
    I will breadboard one such stage and feed it some signal , to see what it does.
    Butler's design, and the Mini Boogee, at least made them amplify and clip, even if they needed to apply *positive* bias to tubes *trying* to make them pass some current at all.

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    Can imagine the question

    As you know in the low and high voltagee operating ranges a tube is far from linear. From an amplification perspective we always learned to design on the range where that tube characteristing is the most linear. In this case we're not interested in linear. we're interested in distorting tubes. BK Butler already found out that with a tube in it's non linear range one can have tube distortion without the standard range of cascaded aplifier stages, and therefore gain, required.

    In this low voltage operating range the tube will not respond in a linear way to an applied signal, not even as a cathode follower. It will be a distorting cathode follower that has limited interest in the signal. That means that it might give some cathode following to the basic signal but has very little interest in the higher frequency components. Therefore it creates wwhat can be considered a filter. Not per se a filter that is defined by it's frequency characteristin but one that is defined by the amount of amplification it does. And the characteristic, is the one of a distorting tube.

    The Radial designer (Couzon?) did a smart move with this one. It will incorporate the tube behavour but is a workaround for the existing "tubes on alow voltage" designs that are around already, BK Butlers's tubedriver, patented up to some 90 volts, Fenders antiparrallel tubediodes (Rock-pro and performer 650 and 1000), Fumio Mieda's patent that can be found in the Vox Cooltron pedals (a real cool one but later than the Radial's btw). All do the same. They use hard clipping and then use a starved plate tube to smooth the hardest clipping.

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    The real fact is that the only function of 12AX7 tubes in Tonebone stompboxes is to provide harmonics, and the two sections of the tube are parallel conected, in a cathode folower configuration with unitary gain.
    The two schematics posted by mozwell it helps, but, the Tonebone Plexitube circuit is more complexe because it has more ICs than Tonebone Classic or Tonebone Hot British.
    I think maybe the problem is a bad contact in a PCB double face trail, because the yellow channel works perfectily!!
    But the red channel fails, after a short time of use.
    Soon, I will try to use a osciloscope and a signal generator to try discover why the red channel have this issue.
    But, if anyone has the original schematic of Tonebone Plexitube, please post here and I thank so much!!

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    I think some of those schematics are incomplete: I've seen internal pictures of some of those Radial Tonebone pedals and at least in "Classic" there is an epoxied section, which someone reverse engineered revealing it hid ordinary SMT clipping diodes that preceded the tube section.

    http://freestompboxes.org/viewtopic.php?f=7&t=4599

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    Let response from my side
    You're right. When I did the reversing of the radial classic a few years back I did measure on the gooped section just to find a shortcut and no resistance or diode crossings to ground or any other net.
    When using a standard DMM in diodetesting function it will show open when there's multiple diodes in series. Not being aware of that I, incorrectly, concluded the goop was a hoax. The reversing in the fsb thread proved me wrong. For that reason I did degoop the goop section in the Hot british. The SO16 IC in there was sanded but gave away it's type by the way it was connected. After that it was just a matter of verification by replacing it with another 4007.

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    Check the loop jack

    If you haven't fixed it yet
    I called them when i had a similar problem , to which they replied that the insert
    or loop jack could become dirty [ mine smelled like smoke from the guy i bought it from
    cleaned the jack , level problem went away .

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    Last edited by okgb; 08-31-2011 at 01:35 PM.

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    Quote Originally Posted by okgb View Post
    If you haven't fixed it yet
    I called them when i had a similar problem , to which they replied that the insert
    or loop jack could become dirty [ mine smelled like smoke from the guy i bought it from
    cleaned the jack , level problem went away .
    Thanks for your reply.

    I fixed the issue resoldering the loop effects jack and making a saphenous bridge at a one thin trail of the printed circuit board.

    So, even after the repairs the Tonebone with the switch in standby it appeared a strange wind noise in the sound.

    So I tryed your sugestion and I sprayed a Contact Cleaner in the jacks of Tonebone and the wind noise disappeared.

    But I tell you, contrary to claims, Tonebone is not a real true bypass, because, the sound of my pedalboard without it is better.

    Recently I build a true bypass looper and I compared the sound with the Tonebone in and out (only in bypass) and with tonebone in the link the sound lacks a few in quality.

    For a real true bypass they should use a 3PDT switch instead of a 2PDT.

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    Old thread but.. I have a love/hate relationship to my plexitube. It's the only distortion pedal that gives me the drive that I want. But it really suck when in "bypass" mode. Measured the input when off and got 2nF. This means the guitar "sees" a 2nF cap. It sucks all high frequencies. Have anyone tried to change the switch. I plan to open it soon but would like to hear if anyone else have fixed this tonesucker.

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