Help with Aion FX Vulcan (Foxx Tone Machine clone)

[neiltheseal]

Hello again.

You were all so helpful with my previous post with the Tone Bender and now I'm moving onto my next failed project.

I bought the Aion FX Vulcan (Foxx Tone Machine clone) which was labelled as "easy", but i have finished soldering and wiring and it doesn't work. Even the LED won't light up. Although I can hear my guitar's clean tone when in bypass.

I have tried reflowing the solder and used an audio probe to try to diagnose the problem. RE the audio probe, i have attached a schematic where I have highlighted where I can detect the signal and it seems to cut out at C4.

I did make some changes to the components based on what I had available. Maybe these are the issue:
C3- asked for a 100n film capacitor but I used a 100n MLCC
C2- I used a 15n polyester capacitor instead of 15n film
D2 and D3 - I used a 1N34A instead of a BAT 46

Does anybody have any idea what I have done wrong? Hopefully it's an obvious beginner fix.

Thanks in advance.

Build docs below in case anyone is interested

https://aionfx.com/app/files/docs/vulcan_kit_documentation.pdf

[neiltheseal]

Here are pictures of the back of the PCB showing off my shoddy soldering work.

[mauman]

None of your substitutions would keep it from working, if you meant C12 = 15n (C2 should be 1n.)

Your audio probe trace suggests Q1 may not be operating.  I'd check voltages and continuity around there, including R2 and R3.

[neiltheseal]

Thanks for your response. You’re right I meant c12.

Sorry if this is an obvious question but how do I test voltage and continuity?

Would I connect the black of a multimeter to ground, set it to dc voltage and then touch the red probe to each leg of a transistor? What readings would indicate it is working?

And continuity, how is that measured?

I did google the answer but there is a lot of assumed knowledge in the answers I found.

[mauman]

Sorry if this is an obvious question but how do I test voltage and continuity?

Would I connect the black of a multimeter to ground, set it to dc voltage and then touch the red probe to each leg of a transistor? What readings would indicate it is working?

Right, with power applied to the pedal, then read DC voltage.  You should see a positive voltage on the collector, and a smaller positive voltage on the emitter.

And continuity, how is that measured?

Remove power from the pedal. Set your meter for ohms/resistance, and put the leads on two points that should be connected either directly or by a resistor.  For example, the emitter of Q1 with red lead, and ground with black lead should read about 1k ohms (the value of R3, which is between that emitter and ground.) Leads on Collector of Q1 and Base of Q2 should read less than 1 ohm, since they're directly connected by a trace on the PCB.   

[BrianS]

Here’s a video that explains how to check voltage on a board that may be of help if you want to watch it.

[neiltheseal]

None of your substitutions would keep it from working, if you meant C12 = 15n (C2 should be 1n.)

Your audio probe trace suggests Q1 may not be operating.  I'd check voltages and continuity around there, including R2 and R3.

Voltage for Q1 is: C 8.26, B 7.50, E 8.19. Is this normal? they all seem to be in a similar range. Same for the other transistors.

Q2 is: C 8.62, B 8.27, E 8.20
Q3 is: C 8.58, B 8.14, E 8.19
Q4 is: C 8.56, B 7.93, E 8.19

R2 - 8.28
R3 - 8.20

I tried disconnecting the power and measuring the ohms between various points. I hope this is the right thing to do:
Q1 collector and base 255k
Q1 Base and emitter 160k
Q1 collector and Q2 base- you're right, about 1 ohm.
Q 1 emitter and ground 992ohm (as you said, about 1k).

Is any of this useful information?

[neiltheseal]

Here’s a video that explains how to check voltage on a board that may be of help if you want to watch it.

Awesome, thanks for that. I think i have the hang of it now.

[Bret608]

The voltages on your transistors look pretty far off. I checked Madbean's Wolfshirt build doc for reference. The Q1 collector and all the emitters and bases are higher than they should be. Could I ask what transistors you've got in there? When they're reading that close to full supply voltage on all pins, it almost looks like they're damaged, which would be hard to do since you've used sockets.

[neiltheseal]

I used the recommended transistors the 2n5089.

I’m not sure how they might be damaged. I guess I’ll try some others and see if that works.

Those numbers did seem off. I checked the transistors on my tone bender (previous build) and these readings were more in line wish what I expected.

Is it possible something else will cause this other than fried transistors?

[EBK]

A broken or missing ground connection, perhaps?

[mauman]

+1 on a missing ground connection.  Start by checking all your grounding - "even the LED won't light up..."

Put your meter on DC volts, and check the DC power jack inputs.  Red probe on +9,  black lead on ground.  If you have something close to 9V DC there, keep your red probe on the red +9V point, and touch the black probe to each of the other ground points on your schematic - on the PCB, the in/out jack shield lugs, etc. If all that's good, let us know.

[jimilee]

Pretty easy to blow a transistor. I’ve done it several times, and honestly on the last build, I think it was the transistors. Maybe a bad batch.


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[Bio77]

My vote is for a wiring or foot switch problem. Do you have the power jack wired in?  Can you post a pic?

[neiltheseal]

My vote is for a wiring or foot switch problem. Do you have the power jack wired in?  Can you post a pic?

You are probably right. I'll have a go at testing the ground connections. Here is a pic of the wiring.