Home Forums GuitarPCB Build Support Red Special problems – no sound

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  • #22370
    e_man
    Participant

    I recently completed assembly of my first GPCB project.  I went with the Red Special.

    The build went together smoothly.  I had to improvise a trimmer connection since the only one I had was a little large for the board.

    I have no sound from the board. I do get hiss that increases and decreases with the volume pot, as well as the tone pot.

    I have checked component values and replaced R3 which was a 510k rather than the 470k called for (I found this after the photo was taken).

    I replaced some of the capacitors (C1, C2, C3, & C7) due to some melted spots (I don’t think they were malfunctioning, I just wanted to be sure.

    BTW, the transistors are socketed. I put fresh ones in while troubleshooting.  They have not been trimmed.  I’ll hit with a little hot glue when I get ready to button it up.

    Anyways, I need more eyes to help figure out what’s going on with this one.

    Thanks for your time and energy.

    #22374
    graham king
    Participant

    You may have done exactly what I did. It was my first too.

    I think the wires on your IN are the wrong way around. 🙂

    cheers

    #22375
    Billy
    Moderator

    We’d need to see and be able to trace the wiring to your DC jack, 3PDT switch and in and out jacks

    Your image is a bit out of focus and you can’t clearly see all the values and resistor colour bands

    #22376
    e_man
    Participant

    Thanks for your comments graham.

    i’m sorry i forgot to mention that i had the connection colors reversed on the input on the board.  A mistake I left uncorrected to prevent one more soldering/unsoldering on the board.

    I am connecting it accordingly when testing.

    Thanks,

    #22386
    e_man
    Participant

    Thanks for your comment Billy.

    I connect my guitar to the input on the board and I connect my amp input to the output on the board.  I have a temp DC connection to power it.  I should get the effected signal from the board.

    I don’t usually install a board in an enclosure until I hear it work.  The footswitch is on a pcb of its own, so it’s pretty straightforward.

    I know there’s only so much to glean from the photos, I was just hoping for something obvious.

    I’ll try to get some better pics up tomorrow.

    Thanks again.

    #22399
    Billy
    Moderator

    I can’t see if R2 has a red multiplication band and R4 specifically the rest look good

    I’m taking it you get bypass sound no problem?

    #22401
    e_man
    Participant

    Well, I haven’t had it in an enclosure yet (I have it drilled and ready but have not installed it).

    I’ll check R2 & R4.

    Thanks for your help.

    #22402
    e_man
    Participant

    Here’s a little better pic.

    Thanks.

    #22445
    e_man
    Participant

    I found the problem.

    Oner of the pads on R3 (the end towards the center of the board) had separated from the trace on the board.  The circuit was open after that point on the board.  You can see the bare copper in the photo I posted above.  Just couldn’t see the forest for all of the trees.

    I found it using a sound source (little mp3 player) and a meter probe to work my way through the circuit.  When i got to the second end of R3 I had sound.

    I drug solder over onto the bare copper trace and all is good.

    I have to say, the pedal’s not bad, but the sag control is something I’m still figuring out.

    And this thing is really noisy!  Maybe I can experiment with pedal order and help some of that.

    Has anyone else that has built this one has any of these troubles?

    Thanks everyone for your help.

    #22461
    Barry
    Keymaster

    This is a super high gain fuzz/distortion.

    I have probably sold a thousand of these boards worldwide over the last 13 years and the forum is relatively silent on issues with building it to answer your question .

    The transistors are rated at 500 hFE to 1500 hFE which is extremely high.

    If it is not boxed up it will most certainly be noisy. After boxing it up and everything is not turned to 10 it should not be any noisier than any other High Gain circuit.

    If it is still noisy I would re-check grounding and re-flow. Additionally you could try using transistors that are measured with a lower gain especially if you happen to have several 1500 hFE ones loaded up.

    #22472
    e_man
    Participant

    Thanks for the info Barry.

    I appreciate the work you put into these circuits.  I’ll be checking the grounding and reflowing the joints.

    Right now, I’m running the transistors spec’d in the build documents.  I think I’ll experiment with some other transistors.

    Thanks again for the info.

    #22476
    Barry
    Keymaster

    Right on the transistors but the margin of tolerance is 500hFE to 1500 hFE which is a huge variance!

    You may want to try other transistors of the same make though is what I was saying. If you have a Peak Atlas or some other testing device you can see where your transistors actually sit in that large tolerance range.

    Idealy you want to go from low to high. Q1 – Q3 respectively. My point was you may have a 1500hFE in Q1.

    Always feel free to try others as well. Just check the datasheet for pinout.

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