Aion Flare Fuzz - No effect signal (pots measuring low?)

[altermanncam]

Hello,

I've been working on this project: https://aionfx.com/project/flare-fuzz-machine/

It is finished but unfortunately I get no effect signal. Bypass signal works when pedal is off. I've tested the 3PDT switch and it seems to be working fine.

There are 8 potentiometers in total. I've found that a good majority of them are not measuring the resistance they are rated at. They were brand new alpha single gang pots from Small Bear electronics.

Are there any reasons these would be measuring faulty/very low resistance besides the pots being bad?


Additional info: schematic called for linear pots. Five (5) 10k pots, One (1) 5K pot, Two (2) 100K pots. Most of my 10K pots are measuring almost no resistance, even when cranked.

Thank you for any information/advice.

[duck_arse]

https://www.diystompboxes.com/smfforum/index.php?topic=29816.0

altermanncam - welcome to the forum. please follow the instructions in the above link, and post up some photos of what you have built.

[altermanncam]

Images are at bottom of post. Link to build documentation and schematic: https://aionfx.com/app/files/docs/flare_documentation.pdf

I followed the instructions very closely, though a transistor did need to be substituted as the one called for was not available.

It called for this part: https://www.mouser.com/ProductDetail/ON-Semiconductor-Fairchild/2N3904TAR?qs=%2Fha2pyFaduh4EnJyiQaKO8k9k9wTxfstUng38uFmGFes%252BShaspW33g%3D%3D

I subbed in this part: https://www.mouser.com/ProductDetail/512-2N4401TAR

Additionally, a 47.5k resistor was used in place of a 47k resistor (R3 in schematic)

I'm not sure if it is a positive ground circuit or not and am not knowledgeable enough to identify this, unfortunately.


Here are measured values of potentiometers when fully engaged:
Volume: 5.24K (5K pot)
Gate: 0.2 ohm (10K pot)*
Drive: 3.5 ohm (10K pot)*
Stab: 1.1 ohm (10K pot)*
Comp: 0.8 ohm (10K pot)*
Body: 85.4K (100K pot)
Tone: 11K (10K pot)
Soft: 0.8 ohm (100K pot)*

*All of these are basically not even there in terms of resistance as far as the circuitry is concerned.



The wiring seems to be correct. The bypass works when the pedal is not engaged. The 3PDT switch tests accurately. Nothing when effect is engaged. Some sound was able to be manipulated with the Stab pot last night, but not this morning.

Any other questions please feel free to ask as I'm not sure what other information may be needed. I hope this is enough for now, though. Thank you.

[altermanncam]

I believe the pots got damaged due to an electrical issue. It seems resistor RPD and capacitor C9 are also faulty.

My wiring follows the schematic (as far as I can see). Is something wired incorrectly? I'm not sure on this one.

[Invertiguy]

Welcome to the forum!

It's very unlikely that all of those pots are actually damaged. My guess is that they're being shorted out by something else on the board. It's usually a bad idea to take resistance readings of components in circuit because the reading will be affected by whatever other components it is connected to. Looking at your pictures, it appears that you didn't trim the component legs after soldering them in place and it's likely that one or more of them is touching something it shouldn't. I'd start by trimming them all back with a good pair of flush-cutters.

[Marcos - Munky]

First of all, welcome.

a transistor did need to be substituted as the one called for was not available.

Not a big deal. Both are general purpose NPN with the same pinout.

Additionally, a 47.5k resistor was used in place of a 47k resistor (R3 in schematic)

So far, so good. You indeed can find a 47.5K resistor, but just use a 47K. Anyway, it'll unlikely have 47K, since they have value tolerance ranges .

Here are measured values of potentiometers when fully engaged:
Volume: 5.24K (5K pot)
Gate: 0.2 ohm (10K pot)*
Drive: 3.5 ohm (10K pot)*
Stab: 1.1 ohm (10K pot)*
Comp: 0.8 ohm (10K pot)*
Body: 85.4K (100K pot)
Tone: 11K (10K pot)
Soft: 0.8 ohm (100K pot)*

*All of these are basically not even there in terms of resistance as far as the circuitry is concerned.

On this one, think again on value tolerance ranges. Some parts have a 1% range, some have 5%, 10%, 20%. Cheap pots have 20%, and alpha isn't a cheap pot. But the circuit should work anyway, just with a smaller setting range. So basically, your volume, body and tone resistances are ok if you measured all those values with the pots desoldered from the board. On the board, other parts will interact with them, and the measured value will be different. As pointed out by Invertiguy, if you measured them on the board, something on the board may be shorting them. I'll take a look on the pics in a while.

Btw, do you know how to do an audio probe test?

[aion]

Are you 100% sure of the pinout of the transistors? I haven't ever seen that type of germanium transistor before and can't find a datasheet, so that would be the one that is most suspect to me. This circuit is pretty simple, so a turned-around transistor is the most likely culprit for no sound at all.

As others have mentioned, definitely trim those leads on the bottom as well.

[altermanncam]

https://www.diystompboxes.com/pedals/hornet.jpg

This is the documentation that came with the transistor pair I used. It was from smallbear electronics. I know it isn't the most concrete method but I did match up the notch on the transistor with the picture etched in the board, but maybe the pinout is different. I'm not familiar with transistors, admittedly, but I can try testing the leads to find out what goes where.

Thanks for the replies, I'll try trimming/cleaning up the solder points first.

I'll update when I can. Thank you!

[altermanncam]

Btw, do you know how to do an audio probe test?

I do not, but I can try looking into this.

[Marcos - Munky]

I took a look on the pics, just forgot to reply. They look good.

But, from your info on the transistors...

https://www.diystompboxes.com/pedals/hornet.jpg

This is the documentation that came with the transistor pair I used. It was from smallbear electronics.

The build notes suggests you to get a Fuzz Face transistor set, which uses two PNP Ge transistors. You got a Hornet transistor set, which is basically a modded Fuzz Face using a Ge (the big one) and a Si (the black smaller one) transistor (which is not a big deal), but they're both NPN instead of PNP. This is a really big deal.

The easiest sollution is suggested on the build notes: use two PNP Si transistors instead, like the 2N3906. As written in the build notes, "This gives a very different character than germaniums and there are plenty of people who prefer this version. It's also much easier to source the parts. Just make sure the pins lines up with the E-B-C pads for Q2 and Q3."

[altermanncam]

Ahhh I see, that must be where the issue is obviously if I'm putting an NPN where a PNP should be. When I was sourcing the parts for the build I just ordered a pair from smallbear without reading much on it, so that's my fault.

Do you think this may have damaged any components in the process or should it be as simple as switching out for the correct transistors?

Thank you for your replies and advice, I greatly appreciate it.