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  • October 4, 2021 at 10:06 am #21002
    Anonymous
    Inactive

    Hi everyone,
    I’ve just tried to build my second effect pedal, the Sunn T. While the process was a lot of fun, I’m afraid it hasn’t worked out (yet).

    My best current guess is that I’ve made a ground short somewhere. The reason I think this is because I have my switch and LED wired using a Musikding pcb. If I connect this to the DC adapter, the LED lights up as expected. If I then however connect the Sunn t board in parallel, the LED turns off.

    What I do not understand is that when I connect my multimeter to the 9v input and ground of the Sunn t board, I read about 2k ohm resistance: had there been a real short, I would have expected to read close to zero.

    Also, if I connect the 9v to the Sunn pcb, and measure the voltage across the 9v input and ground, I read approximately 0.8v?

    Ive been told that wiring is the most likely candidate for a mistake or short, so I’ve checked the resistance between all the spots where I’ve wired in the pots: none of them are 0.
    I’m at a bit of a loss on how to continue. Is there anybody here that has any ideas?

    October 4, 2021 at 11:33 am #21005
    Barry
    Keymaster

    The Ground Between you wiring board and the Main Board are not connected consistent in the photos.

    This leads me to believe they are just laying loose on the boards. They need to be soldered and connected to each other.

    So make sure you are soldering +9v wiring and Ground wiring so there is constant connectivity between the two boards.

    Then I would start biasing the transistor voltages.

    October 4, 2021 at 11:54 am #21006
    Anonymous
    Inactive

    Hey Barry,

    thanks for your reply. I had indeed unhooked those wires for testing. I’ve now soldered them back in.
    The build guide says to bias the transistors to around 5v, but if I turn my trim pot all the way open I read about 0.8v again. Also the LED won’t light up anymore now.

     

     

    October 5, 2021 at 6:53 am #21030
    Anonymous
    Inactive

    I’ve found the error!

    I had installed diode D2 the wrong way around, as well as installing all the trim pots in the wrong orientation. Going out to buy some replacement parts now, will update you on whether this solves it, but it definitely explains it!

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