My talkbox really needs a proper mod

Discussion in 'General Electronics Chat' started by musicalavtech, Feb 27, 2016.

  1. musicalavtech

    Thread Starter Member

    Mar 23, 2012
    32
    3
    This talkbox can switch from the internal driver output (through the tube that would be hooked up to it), or it would be switched to the internal 5W amp output going to a speaker cabinet. It also has a non-switchable connection from the input, to a preamp output jack, to plug into my rack rig. Really the 5W amp output isn't used by me.

    I would like to instead, be able to toggle switch between the "talkbox" mode and the PREAMP output. I can re-route the input circuit to the switch.....but, on the switch, there is a jumper (under the left red arrow). This is only jumping ground. No matter what the toggle mode is, the ground is always there. I don't understand why a jumper can't be used instead, right on the pc board where the 2 black wires attach underneath. I could free up half this switch to make my mod work.

    My only question is about that jumper being wired on the switch. Is it a bad idea to simply jump those points on the pcb?



    [​IMG]
     
  2. musicalavtech

    Thread Starter Member

    Mar 23, 2012
    32
    3
    Well I've found a schematic just a bit ago, and it seems if I cut that jumper on S1, then the unit will operate like I desire. In theory anyway. No jumper is shown in this schematic.

    [​IMG]
     
  3. #12

    Expert

    Nov 30, 2010
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    6,852
    There is a butt load of problems here.
    Not according to the schematic.
    Not according to the schematic.
    The schematic says it already does that (minus the pre-amp stage).

    ps, D6 is drawn backwards.

    According to the schematic, S1 chooses between the power output stage and a straight wire bypass. Your description is so unlike the schematic that I can't interpret your request. With this many inconsistencies, your verbal description of the circuit board becomes worthless because there is no way to connect your words to the schematic and point out the wiring in question. I would need to have this thing on my work bench to figure out which is wrong...you or the schematic. We are having a very bad communication problem today.
     
  4. musicalavtech

    Thread Starter Member

    Mar 23, 2012
    32
    3
    As it goes, the jumper on the switch permanently allowed the relay to always be energized, causing no output to the preamp out. The jumper on the switch in the picture is not shown on the schematic. It could be integrated as another switch on the unit to provide output options. Also the red, white, and black wires from the switch to the pcb, deal with switching the amplified sound to the driver, or toggled to the powered output jack (when a spkr cable is plugged in). These wires are also not shown on the schematic.

    I've cut the jumper and got the results I need.
     
  5. #12

    Expert

    Nov 30, 2010
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    That makes sense. Relay on = stuck in power output function.
    Does all this mean you don't have the foot switch described in the schematic? I mean, with S1 shorted, a foot switch wouldn't have any effect.

    It is so difficult when the schematic doesn't match the product!:mad:
     
  6. musicalavtech

    Thread Starter Member

    Mar 23, 2012
    32
    3
    Just half of S1 was shorted. The half that grounds the relay. The other half of S1 directs the powered signal to the amp out jack, or toggles to the internal driver. That side was never shorted with any jumper.

    Yes it is frustrating when the "as built" diagrams don't match what actually ships out. But of course the manufacturers have the right to revisions without proper documentation. I see it at work all the time.
     
  7. #12

    Expert

    Nov 30, 2010
    16,355
    6,852
    OMG yes. I have been rehabilitating a Ford Explorer this winter and the wiring has so many differences from the 300 pages of drawings!
    The wiring book was published September 2004, the car was build in October 2004, and there are so many, "not according to the schematic" results that most of what I am doing is bypassing the original design and leaving nothing but the manual switches working.
     
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