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Pedal Building Power Supply Weirdness...

Discussion in 'Burnt Fingers DIY Effects' started by maj34, Dec 2, 2020.

  1. maj34

    maj34 Tele-Meister

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    I started doing some pedal building.

    I dove in the deep end: Etching, tinning, and doing my own silkscreens with the laser printer; designing my own PCBs in Eagle; every last part needed to build a batch of 5 pedals.

    So far I've completed a Tonebender Mk2 and I have a Fuzz Face on a breadboard that is sounding great.

    I've encountered two weird issues that I cannot explain:
    1) My Tonebender will not work with the high impedance input on my Vox AC4HW1. Low impedance works great. Tried 2 other amps, works great. High Z input on the Vox = dead silence as if amp input is shorted to ground. It's not the cable!

    2) My fuzz face will not work with my homemade power supply. I have a very simple but incredibly useful homemade power supply. It's 8 rechargeable batteries, a LDO regulator to give me 9V, and a typical Boss style barrel power plug. I have used this for years with dozens of different pedals. My breadboarded fuzz face (which has the barrel power receptacle) will work perfectly with a wall-wart, but my power supply will not turn it on.

    Both these things are real head scratchers (for me anyway).

    Anyone?
     

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  2. LightningPhil

    LightningPhil Tele-Meister

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    No idea about q1. Though suggest plugging a cable into the amp and messing across the jack at the free end of the cable. Should read 1Meg ohm. If not, investigate the amp.

    For q2. Is there any PSU filtering on the tone bender? Try a ferrite on the cable and a bypass cap across the input of the pedal. Your LDO might be generating RF. Are there caps around it (on the pins)?
     
  3. Norris Vulcan

    Norris Vulcan Tele-Afflicted

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    Sorry to state the obvious but nothing's shorting to the enclosure is it ?
     
  4. Peegoo

    Peegoo Poster Extraordinaire

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    1. Safe to assume the guitar works fine plugged straight into either the HI and the LO inputs on the Vox?

    2. What is the current draw of the Fuzz Face? Is the battery pack able to deliver the current required?
     
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  5. ThermionicScott

    ThermionicScott Poster Extraordinaire

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    You sure that your power supply is the right polarity?
     
  6. maj34

    maj34 Tele-Meister

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    Hi all, thanks for the replies.

    I fixed some of my issues:
    The "tonebender won't work with high impedance input on Vox High Z" issue: This was an issue when I had the circuit on a breadboard. I tried again with the boxed pedal and it no longer does it! I can't explain it, but it's no longer an issue.

    I still can't explain why my homemade power supply doesn't want to power my breadboarded Fuzz Face. It definitely is right polarity. It definitely supplies enough current for the fuzz face (I designed it for 1000mA and regularly use it to power 8-10 pedals).
     
  7. Digital Larry

    Digital Larry Friend of Leo's

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    I'd recommend a few useful tools if you don't already have them.

    a) Digital multimeter will help you confirm that voltages, like power supply, are really getting to where you need them and are the right polarity.

    b) If you wish to spend a lot of time doing this, I'd invest a couple hundred bucks in a 2 channel digital scope. I hang out over at diystompboxes and while I understand that a scope is expensive and maybe somewhat challenging to learn how to use, working without one is a good way to waste hours of time. Not all circuit problems are immediately visible.

    I'd be more likely to help if you sent a schematic. The polarity of a fuzz face power supply would be suspect because the germanium ones anyway use "positive ground" as a result of most Ge transistors being of the PNP flavor. A Fuzz Face is pretty simple so either:
    a) Bad connection somewhere
    b) wrong polarity
     
  8. maj34

    maj34 Tele-Meister

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    Thanks Larry.

    Yes, I have a dmm, lcr, and a few other goodies. Been trying to justify a digital scope for years, especially at the prices of some of the cheaper ones like Hantek... But then I wonder if it's worth upgrading a few hundred dollars to a company that might have better support if it was ever needed.

    My fuzz face and tone Bender are stock GGG npn silicon versions. Nothing exotic there. Don't have a schematic for my power supply but it's very simple: a 9v ldo, 8 batteries, a switch, an led and resistor for led. I didn't use input and output caps so it's possible there's an instability there but I doubt it.
     
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