Home Forums GuitarPCB Build Support Apollo tremolo troubleshooting

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  • #18253
    Addison
    Participant

    I’m working on the Apollo tremolo circuit, this is my fourth pedal. I have all the components and everything soldered, but there is no signal coming through when I engage the circuit. I have built an audio probe, and my signal stops coming through after OC1 (NSL-32). I was wondering if there was an audio path diagram for this circuit that I could use to continue troubleshooting. thanks!

    (the circled pin is the last one that the signal comes through on)

    #18256
    wilkie1
    Moderator

    If you have signal after the optocoupler, then it passes through R17 to the last OPAMP stage.  You should then have signal at pin 1 of the opamp.

    Is the LED blinking? This would indicate that the LFO is working.  Do you have voltage at SW2?  That is necessary to feed the opto when the kill switch (SW2) is actuated.

     

    If these answers are “NO” report and we will continue.

    #18259
    Addison
    Participant

    I do not have signal at R17 or the opamp, and the LED is not blinking. I do have voltage at SW2 (18.5V). Thanks for the quick reply!

    #18272
    wilkie1
    Moderator

    I hope you have capacitors with a voltage rating of 25V or higher since you are using 18.5 V  The circuit is originally designed for a 9V supply.

    Without the LFO working the signal cannot pass through the optocoupler  To troubleshoot, we will need clear pictures of both sides of the board, views of the off board wiring, and voltages.

    Use the schematic to assist in reporting components and values.  The signal path is simple to follow from the IN jack to the OUT jack.  The LFO circuit controls the optocoupler that acts as a “Gate” to control the signal flow.

    We are here to help.

    #18495
    Addison
    Participant

    Turns out my power source is only 9v and I was reading my multimeter wrong. my voltage at SW2 is 9.18v. here are some photos of my board:

    #18497
    Barry
    Keymaster

    Photos are very hard to see. Even when zooming in.

    Update Edit: I think the photos are that way because they are side by side.

    I am trying a straight format here:

    #18500
    wilkie1
    Moderator

    The photos only show an LED installed at the foot switch.  The LFO status LED, D1 is not installed in the photos.  Although it is not needed for the circuit to function, it helps to indicate the speed of the LFO.

    Set the Speed pot and the GAIN trimmer to mid point.  Measure the voltage at the middle lug of the DEPTH pot.  It should be varying.  Check that the KILL switch SW2 is not in the KILL position.  Check the orientation of the optocoupler.  The + mark must be installed correctly.

     

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