Author Topic: Quadratron not passing signal  (Read 3594 times)

Mbornhoft77

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Quadratron not passing signal
« on: September 05, 2022, 06:33:20 PM »
Hey Everyone, I am new to the forum and I am here because I am having issues with my Quadratron build from AionFX. I'm fairly new to pedal building but I have built the Helios, Andromeda, Flare, IVP Preamp, EP-1 Preamp, KOT clone, Duelist clone as well as a handful of pedals from BYOC and General Guitar Gadgets. The issues I am having with the Quadratron is that I can not get it to pass signal...silence. I am powering the unit with a Damage Control 9 volt power supply and all LEDs light up when engaged. The LEDs for the LFOs also light up and seem to be working with the 5 switches. I've tried other power supplies, different cables, and a few different amps. I've verified all caps, resistors, diodes, and IC chips and double checked their values and everything is in its right place. I've reflowed solder to all components, checked the wiring, then rewired it all to not avail. I know I need to check the values of all the IC chips, set the multimeter to DC, anything above 20 V but my readings seem to be all over the place. I'm running the pedal alone through a Fender HRD using a 2019 Gibson SG.

mauman

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Re: Quadratron not passing signal
« Reply #1 on: September 05, 2022, 09:36:48 PM »
Welcome! 
Schematic and BOM: https://aionfx.com/app/files/docs/quadratron_documentation.pdf
Does it work in true bypass?
Does it work in buffered bypass?
If not, that narrows it down.
If so, check pin 8 of each op amp for +9V.  If that's present, the next step might be an audio probe to trace the signal path starting at the input.  Instructions are at https://aronnelson.com/diywiki/index.php?title=Debugging if you're not familiar with that.

BTW, you've equipped both C10 and C11, only one of them is required, although that shouldn't kill the signal.
« Last Edit: September 05, 2022, 09:48:09 PM by mauman »

Mbornhoft77

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Re: Quadratron not passing signal
« Reply #2 on: September 06, 2022, 05:38:06 PM »
Thank you for the reply! I did try the the pedal in both true and buffered bypass and it still wont pass signal. I also removed the cap at C10.  I checked each op amp on pin 8 for +9V and on 1,2, and 3 they all measured 8.05-On 4,5, and 6 they all measured 8.47
I have never done an audio probe of a circuit before...I don't even know how to read a schematic, but I love building pedals and I'm willing to learn more and put in the work to figure this out. Guess its time to build a audio probe! I don't know if this will help but here are some more pics of my build.

jwin615

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Re: Quadratron not passing signal
« Reply #3 on: September 06, 2022, 06:16:57 PM »
Are you tip and sleeve reversed on the input or output?
Hard to tell in the photo but kinda looks like the in is reversed.

Mbornhoft77

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Re: Quadratron not passing signal
« Reply #4 on: September 06, 2022, 07:28:18 PM »
I did try disconnecting the wires going to the inputs and outputs and switching them but that didn't seem to work. I rewired it as per the instructions from AionFX and this is how it currently looks.

jwin615

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Re: Quadratron not passing signal
« Reply #5 on: September 06, 2022, 08:24:13 PM »
That all looks good. Only other thing I see visual is maybe the ground on the 072 in ic4.(leg 4) looks a little lifted in the photo, but should be making contact.
Do you get signal through to the dry out jack?

mauman

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Re: Quadratron not passing signal
« Reply #6 on: September 06, 2022, 08:26:18 PM »
<edit: to clarify, if you're saying it doesn't pass signal in true bypass mode, while it's bypassed...> If it won't pass signal on true bypass, the problem is somewhere between the input jack, bypass 3PDT stomp switch, true/buffered bypass slide switch, and output jack.  That's all that's in the signal path (plus connecting wiring) during true bypass.

Are you sure the bypass 3PDT isn't rotated 90 degrees? You can tell by checking continuity between pairs of pins.  With no power applied, check for less than 1 ohm of resistance between the middle row of pins and either the upper or lower row (the connection should flip from middle+upper to middle+lower when you toggle the switch.)  If it's rotated, you'll have continuity between the middle column and the left/right columns.   
« Last Edit: September 06, 2022, 08:33:26 PM by mauman »

LaceSensor

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Re: Quadratron not passing signal
« Reply #7 on: September 07, 2022, 02:30:02 AM »
edited. not sure whats going on here, but common issues with Lovetone Doppelganger clone builds are mis-wiring of the EXP controls which kills the LFO - seems you dont have that issue, and you would still get signal (bypass and engaged) even if the LFO was borking out.

Sound more like the footswitching wiring is off, or your shunting signal to ground somewhere.
I assume its just dead quiet, and not buzzing/noizy?

With a signal probe you will be able to figure out where the sound is being lost. Essential item !
Also as above IC4 looks sketchy but thats part of the LFO IIRC correctly, so maybe a red herring. still worth re-seating regardless


« Last Edit: September 07, 2022, 05:47:17 AM by LaceSensor »

jwin615

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Re: Quadratron not passing signal
« Reply #8 on: September 07, 2022, 06:50:17 AM »
+1 from Lace.
Probe would make easy work of it.
Check switching first. In true bypass mode, pedal off:
Check between center and top bottom on bypass switch as Lace said.
If they are not rotated and correct-
check continuity from input to bypass switch, DMM set to ohms, tip of
IN jack to C2 on bypass switch.
With the bypass switch set to where there is continuity between C1 and C2, check resistance between C2 and A2, then C2 and output jack tip. All measurements should be near 1 ohm.

Mbornhoft77

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Re: Quadratron not passing signal
« Reply #9 on: September 08, 2022, 07:22:29 PM »
Wow...Thanks to all of you for such excellent and insightful information. This is the first time I have posted to a forum and it has been such a positive experience. To jwin615 and LaceSensor, you guys have eagle eyes! I never would have noticed that lifted leg on IC 4. As soon as I pulled it up it I saw how wonky it was. So at this point I replaced both footswitches with regular lugs instead of the PCB pins that I had previously installed. This was the first time I used footswitches with PCB pins because I thought they might work better and be easier to install. I also replaced the mono jacks with stereo jacks to see if that might help. Without the pedal engaged it did finally pass signal. With the pedal set to true bypass and then engaging the pedal it does not pass the signal. When set to buffered bypass and plugging into the dry out and connecting it to a second amp it does pass signal to both amps...until I engage the pedal and unfortunately there is silence. 

Mbornhoft77

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Re: Quadratron not passing signal
« Reply #10 on: September 09, 2022, 05:38:48 PM »
I built an audio probe and traced the issue to the footswitch PCB. I was too aggressive with the desoldering iron when removing the footswitch and messed up the solder pads. Thanks again to everyone for all the help.

mauman

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Re: Quadratron not passing signal
« Reply #11 on: September 09, 2022, 07:36:59 PM »
Congrats!  We've all been there.

gordo

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Re: Quadratron not passing signal
« Reply #12 on: September 09, 2022, 07:50:46 PM »
Add one to the win column for the good guys.  Glad you worked it out and glad everyone was able to help out.  It's crazy to think that I spent any time without an audio probe, it's been a key to easy troubleshooting.  I like Madbean's version once you get the hang of it and I have this ancient old audio generator that's the size of a toaster that I'm hoping to eventually replace.
« Last Edit: September 09, 2022, 07:54:30 PM by gordo »
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Mbornhoft77

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Re: Quadratron not passing signal
« Reply #13 on: September 09, 2022, 08:46:29 PM »
I honestly can’t believe how easy it was to diagnose the issue using the audio probe. I thought it would be this long, arduous process. I checked the rest of the main PCB and it’s solid. So…it would be possible to wire the 2 foot switches, 2 resistors, 1 cap, true/buffered bypass switch, and LEDs without using the PCB foot switch, right? It’s just a matter of following the traces to their respective components and probably some jumpers and wiring to the foot switches? I am so determined to get this thing working before the weekends’ done. The new episode of the JHS Show is entitled, ‘You Need A Phaser.’ It’s taunting me.

jimilee

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Re: Quadratron not passing signal
« Reply #14 on: September 09, 2022, 09:42:37 PM »
You need as many phasers as possible. I have about 36 so far. I sold a bunch several years back.


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