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
Here are pictures of the back of the PCB showing off my shoddy soldering work.
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.
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.
Quote from: neiltheseal on December 14, 2022, 10:57:36 AM
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.
QuoteAnd 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.
Here's a video that explains how to check voltage on a board that may be of help if you want to watch it.
https://www.youtube.com/watch?v=idWhtCU7xw0
Quote from: mauman on December 14, 2022, 05:04:48 AM
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?
Quote from: BrianS on December 14, 2022, 01:56:54 PM
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.
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.
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?
A broken or missing ground connection, perhaps?
+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.
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.
Sent from my iPhone using Tapatalk
My vote is for a wiring or foot switch problem. Do you have the power jack wired in? Can you post a pic?
Quote from: Bio77 on December 19, 2022, 04:36:18 PM
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.
Quote from: jimilee on December 19, 2022, 04:04:18 PM
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.
Sent from my iPhone using Tapatalk
I don't think it was a transistor. I put them into the sockets of another pedal and it worked fine. WIll look into the grounding issue.
Quote from: mauman on December 19, 2022, 12:31:11 PM
+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.
This looks promising. I connected the red probe of my multimeter to the + of the 9v battery, then touch the negative of the battery with the black: reads about 8.3v. Makes sense.
Then with the red still connected to the + of the battery I touch the ground of the dc power input and it reads 0.51. This should surely read about 8v too right?
The LED is in backwards so about to fix that. However this should not really affect the circuit right?
Quote from: neiltheseal on December 22, 2022, 08:47:37 AM
This looks promising. I connected the red probe of my multimeter to the + of the 9v battery, then touch the negative of the battery with the black: reads about 8.3v. Makes sense.
Then with the red still connected to the + of the battery I touch the ground of the dc power input and it reads 0.51. This should surely read about 8v too right?
That would definitely point to a grounding issue. You should have direct continuity between battery negative and DC jack ground, provided there's something plugged into the input jack (which makes the battery ground connection through the jack sleeve).
Quote from: neiltheseal on December 22, 2022, 08:47:37 AM
The LED is in backwards so about to fix that. However this should not really affect the circuit right?
Nope, it just wouldn't light up is all. No damage to the LED or the rest of the circuit.
When you are testing the voltages with a battery you need an instrument cable (1/4 inch) to be plugged into the input jack. There is a ground disconnect there to save the life of your battery when the pedal is not plugged in.
Also, can you post a pic of all the wiring (both sides)? Try to move the wires so it is clear where everything is going.
Quote from: Bio77 on December 22, 2022, 05:51:48 PM
When you are testing the voltages with a battery you need an instrument cable (1/4 inch) to be plugged into the input jack. There is a ground disconnect there to save the life of your battery when the pedal is not plugged in.
Also, can you post a pic of all the wiring (both sides)? Try to move the wires so it is clear where everything is going.
Good idea i'll do that with the input.
Here are a few pics of the wiring and front/back of the PCB.
I have voltage when I check the DC output now. Not sure what was going on before.
https://imgur.com/gallery/IH7ZXtp
I have also noticed that if I touch the ground on the guitar input lead to any of the other connections (which I assume are both input) then the LED lights up. Is this normal?
Quote from: neiltheseal on December 23, 2022, 02:53:35 AM
I have voltage when I check the DC output now. Not sure what was going on before.
https://imgur.com/gallery/IH7ZXtp
Actually this depends where I connect the ground. If connected to the - of the battery then I get around 7.10v on the ground of the dc input.
Although I get about 7v on pretty much anywhere I touch, PCB, input/output jacks etc. Is this normal?
But I connect the black lead to the ground of the input/output I get no reading.
Thanks for all your help everyone. I have learned so much.
As expected, the issue was a simple one that is my fault: the battery wasn't properly connected!
I randomly tested it out with DC inout instead of battery and it worked! Sounds fantastic too.
I couldn't get the battery to work so just removed it. Happy to have a working pedal.