Dalek Voice Mod

Discussion in 'General Electronics Chat' started by Mark_Norwich, Jul 5, 2019.

  1. Mark_Norwich

    Thread Starter New Member

    Jul 4, 2019
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    I have an old circuit, a MkIIIb Dalek Voice Mod from the Project Dalek forums.

    The actual mod works (of a fashion) and I do get a modulated Dalek'esque output. There is also a sound to light output that doesnt work at all. Pot 1 controls the level at which the sound to light is triggered.

    Pot 2 is the modulation control, Pot 3 is Volume.

    Ive looked back on the ProjectDalek forums to see if I can find any circuits but can only find dribs and drabs, I know that @bertus was involved and has said he can pick up the thread here.

    I'll post what pics I can, sorry, Im a very basic Electronic knowledge so bear with me. Apologies if these are the incorrect specific diagrams but they should give you and idea of whats going on.

    ' inputs-outputs.jpg post-3215-1257434933.png post-3215-1257435159.jpg

    20190627_152501_resized.jpg 20190627_153021_resized.jpg 20190627_153157_resized.jpg 20190627_153200_resized.jpg 20190627_153207_resized.jpg 20190627_153209_resized_1.jpg
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Did the sound to light ever work?
    It could be that there is an problem with the optocoupler or the mosfets.

    Bertus
     
  3. Mark_Norwich

    Thread Starter New Member

    Jul 4, 2019
    14
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    Yes, the sound to light did work, the LED leight is permanently on though now and the on/off switch doesnt seem to control anything even though it as all wired up.

    Voice still works though and can be modulated.

    Im guessing the Optocoupler will be the 4N35?
     
  4. Mark_Norwich

    Thread Starter New Member

    Jul 4, 2019
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    Also found these from another post on here:

    VM_copper_side.jpg VM_bare_pcb.jpg sound_to_light_with_envelope_detector_small.jpg post-3215-1257435159.jpg New_VM_with_tone_control.png
     
  5. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    Check the Voltages at Q1, Q2, Q4 bases..
     
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The led D4 is supposed to be an 12 Volts led (with build in current limiter) or a led with an 1K resistor in series.

    When the lights are on permanent, check the mosfets for shorts.

    Bertus
     
  7. Mark_Norwich

    Thread Starter New Member

    Jul 4, 2019
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    The Exterior 12v dome lights dont come on at all, The switch has no effect on the LED. LED, I think, used to flash in sync with the dome light output so you had a visual reference to the rate as you were talking from inside the Dalek.
     
  8. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The sound to light is dependend on the volume of the speaker output.
    Could you remove the optocoupler (IC5) and place a jumper wire between pin 5 of the optocoupler to pin 7 of the LM358 (IC1)?

    Bertus
     
  9. Mark_Norwich

    Thread Starter New Member

    Jul 4, 2019
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    The speaker output seems fine and is at mid volume at present. Just no dome lights. Ive ordered a new Opto chip
     
  10. Mark_Norwich

    Thread Starter New Member

    Jul 4, 2019
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    what am i looking for Bertus when I link Opto Pin 5 to IC1 pin7 ?
     
  11. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    When you link those pins, the signal goes from the preamp to the sound to light circuit directly.
    The opto MUST be removed in that case.
    You can not set the sensitivity of the sound to light, but can see if the rest of the sound to light is working.

    Bertus
     
  12. Mark_Norwich

    Thread Starter New Member

    Jul 4, 2019
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    ok, that done, no change at all. nothing.
     
  13. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The gain might be to low.
    And what happens when you move the wire from pin 7 of the LM358 to one of the speaker outputs (it does not matter wich)?

    Bertus
     
  14. MisterBill2

    Distinguished Member

    Jan 23, 2018
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    If the LED indicator (D4) is illuminating but the two light bulbs are not, consider that they are shown connected in parallel. The circuit drawing shows that. So the first thing to check is the connections in that area. I do not see any switch in that first circuit drawing and so I can not comment on that. what voltage do you measure across the D4 LED? If the two lights are not also lighting then they may have failed, or there may be a broken connection. So that is where to start looking for the problem.
    In searching for a circuit problem it is far more efficient to understand at least a bit of the circuit rather than blindly look for things that may have failed. In this instance the fact that the lights are off while the LED is lit indicates some sort of problem jn that part of the system immediately. Next would come an examination of the connections to the FET devices, followed by checking the drain, gate, and source voltages on the FETs.
     
  15. Mark_Norwich

    Thread Starter New Member

    Jul 4, 2019
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    Ive ordered a few IC5's i'll do a straight swap first on one of those. I do notice though that the TDA2003's are getting a bit warm.
     
  16. bertus

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    Hello

    That the TDA2003 is getting a bit warm is nothing to worry about
    They are power chips and have a heatsink mounted

    Bertus
     
  17. MisterBill2

    Distinguished Member

    Jan 23, 2018
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    In addition, those TDA2003 devices are part of the sound portion and have nothing to do with the lighting function. THAT is why diagnostic servicing requires being able to understand the system and how it functions. If the connections to the external lights are right, then check the lights themselves to verify that they have not failed. Looking at the circuit it is obvious that the lights are directly in parallel with the D4 LED, which the TS states is staying lit. Unplugging IC5, if it is not soldered in, would provide a quick check of the whole string of directly connected transistors. Then check the voltage at the junction of R27 and R28. That voltage controls the power FET devices. If that voltage is close to zero then they should both be off, which should have the LED not illuminated.
     
  18. Mark_Norwich

    Thread Starter New Member

    Jul 4, 2019
    14
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    Thanks MisterBill - as I said, I'm no electronics genius here. I'll follow those instructions though.

    I did remove the IC5 earlier and the LED light was still on but I'll check the voltages at R27 and R28 and report back ;)
     
  19. Mark_Norwich

    Thread Starter New Member

    Jul 4, 2019
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    I made an error on the above comment(s) - The IC I removed and have re ordered is IC4 the 4N35 optocoupler.

    Do you still want me to remove IC5 which is is a TDA2003 ?
     
  20. Mark_Norwich

    Thread Starter New Member

    Jul 4, 2019
    14
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    OK IC4 removed (4N35) - LED still on and receiving 12v - Measured the voltage to base of R27 / R28 and that shows as 0.6v

    Cant see any obvious shorts on the circuit anywhere.

    20190706_114531.jpg 20190706_153056.jpg 20190706_153108.jpg
     
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