Aion Phobos trouble... Sound when bypass, nothing when engaged.

[boris819]

Hi guys !

Super new to the pedal building world, but kinda gets some of it. Wife got me a Aion Phobos for christmas, and I love the concept of building my own pedal, but so far, I get sound when bypassing the pedal, and none when engaging it.

Here's the documentation : https://aionfx.com/app/files/docs/phobos_kit_documentation.pdf *** Note that the PCB slightly changed. R4 and R5 swapped. (see image below)





From what I heard, here's the best way to proceed :

1.What does it do, not do, and sound like? I get sound when bypassed only.
2.Name of the circuit = Aion Phobos, based on Tone Bender Mk. III
3.Source of the circuit (URL of schematic or project) = https://aionfx.com/app/files/docs/phobos_kit_documentation.pdf
4. No modifications of substitution at all.

So, first of all, I'm more than happy to give you some readings of the components, but when finding a good 'how to ask for help' guide, I landed on this, saying to give the 'C=?, B=? and E=?' but I don't know what C, B or E are... Sorray, newbie here.


Also, here's some photos of the circuit, in the pedal. I obviously disconnected the I/O pcb to get clearer images.













THANKS IN ADVANCE GUYS ! And sorry for the lack of experience, trying to learn the basics first and then get to enjoy it, once I understand it.

[eh la bas ma]

Hello, welcome !

I built this Phobos/Tonebender project, i did the MKIII version, it's great !

Your board is the newest revision i guess, looks even more amazing than the older Phobos boards.

About transistor pinouts :

Look for the name of your transistors. It can be written on their bodies, otherwise look for the order when you or your wife bought them.
If it was a kit, look for the BOM and find the transistors names.

Once you know their designations, google them : "AC125 pinouts" for exemple. or "AC125 datasheet"

Then you'll find a picture of the transistor with Collector, Base, Emitter designations for each legs. And you'll know how to install them with the right orientation.
exemple:

I can see some suspicious soldering joints on your build.



Iron set around 400°C.

The trick is to touch simultaneously with your iron, both the component's leg and the pcb pad for 1 or 2 seconds. Then add a bit of solder to fill the pad. Remove the iron going upward, along the component's leg. That's how you get a dome-shaped solder joint.

You don't want to overheat the pcb or some heat-sensitive parts, so be quick when reflowing pads (3 or 4 seconds max), and remove all ICs and transistors in the aera.

If you have some bubble-shaped soldering joints, you'll need a desoldering pump to suck off some of the solder on these pads. Then reflow the pads and add some solder if necessary, to fill the pads. Not too little, not too much.

Check for short-circuits, use your multimeter on continuity mod to check if two pads are connected. Look at schematics to see if components should be connected or not. Move quickly the tip of your iron between pads to clean the tiny spaces between them (again, you don't want to overheat anything).

The middle pot should be insulated to prevent it from shorting with the pcb soldering side. A piece of cardboard or plastic between the pot and the board, or some thick plastic tape on the back of the pot should be enough.

[duck_arse]

also welcome. I think that circled track might be scuffed thru. it looks to be connecting the input signal to the circuit, so you should check for continuity with your meter [power OFF] between the upper and lower solders. if it is open, you can bridge across the gouge with a resistor leg cut-off.

also - search hereabouts for the audio probe, make one of those. it will aid all your future problem solvings.

[ElectricDruid]

If that's it, that's an *insanely* good spot, Duck

[boris819]

Hi guys ! Thanks for the replies !

First of all, it's unfortunately not just the scuff.. would have been such a good spot indeed ! I built an audio probe yesterday and figured some things. I now got sound, but it's really quiet so I'm going to keep going through the circuit to figure out where it bugs out.

Thanks for the help !

[duck_arse]

but was that track open? we must know.

[boris819]

Hahahaha no, it was all good actually.

Btw, I found out a part of the problem with an audio probe as suggested ! I've got sound, but it's pretty quiet !

I found out that maybe it's one of the germanium transistors that might be faulty... Is it normal that with my audio probe, I don't get sound on one of the legs ? I get sound out of all other legs from other germanium transistors.. Just not one of the last transistor's leg. Also, from what I understand from the schema, it's after that one that there is a huge audio drop. Would it be possible the transistor is faulty ? I absolutely made sure not to overheat it during solder, knowing it can be a thing.

[ElectricDruid]

The last transistor, Q3, has one of its legs tied to ground, so if that was the one you're talking about, you'd totally expect one leg to have *no sound at all*.
If you've got decent signal on the other two legs of Q3, I'd have a check around the tone components and volume pot soldering.

It sounds like you've made some good progress with it already, so well done. Nearly there!

[duck_arse]

I've just noticed that your built board layout doesn't match the build docs, over near the input section. I don't care, but. and the one resistor I want to see, right at the top of the board, is obscured by that cap. nevermind, it's prolly not the one thing.

measure resistances to ground, please, and note your answers here. from both sides of C5. from both sides of C6. from the juntion of R10 and level pot. please.


I've been messing w/ a buzzaround alike on the breadbord, quite similar to the mkIII, and it doesn't have a level control. and is insanely loud, when it wants to be.

[aion]

I've just noticed that your built board layout doesn't match the build docs, over near the input section. I don't care, but. and the one resistor I want to see, right at the top of the board, is obscured by that cap. nevermind, it's prolly not the one thing.

I made a few minor layout adjustments late last year so it would be easier to fit different types of transistors, and this appears to be one of them from before the update, but it was just repositioning a few parts (the schematic itself hasn't changed at all).

I found out that maybe it's one of the germanium transistors that might be faulty... Is it normal that with my audio probe, I don't get sound on one of the legs ? I get sound out of all other legs from other germanium transistors.. Just not one of the last transistor's leg. Also, from what I understand from the schema, it's after that one that there is a huge audio drop. Would it be possible the transistor is faulty ? I absolutely made sure not to overheat it during solder, knowing it can be a thing.

I do audit every transistor that goes out to ensure it biases correctly in the Mk3 circuit and sounds right - so I would say it's 10:1 odds it's something other than the transistor. It's not impossible - shipping damage or other age-related maladies - but as long as the transistor looks OK visually, I would focus on the surrounding components rather than Q3 itself.

If you've ruled out the obvious issues (voltage & biasing, swapped components, etc.) then I would go through and reflow all of the joints on the main PCB, which will usually clear up either cold connections or microscopic shorts between traces. If bypass works, you can rule out any issues with the I/O board and most likely the footswitch board as well.

[idy]

I don't think the OP has really assured us of the identity of the Qs, and whether their pinout matches the board.
Hey, OP, what kind of transistors are those anyway? What is written on them? Once you know that, confirm what the pinout is...
Aion seems to say this is a kit and the transistors are chosen to fit the pinout..unless one is in a different kind of package....And he also says there is a PCB which accommodates more than one pinout...

[duck_arse]

he has posted some good photos tho, I can see MP24A on one and ....4A and M.... on the others. transistors look right to me from this distance.

I don't much like the look of that melt-hole in the 2n2 cap, though.

[aion]

he has posted some good photos tho, I can see MP24A on one and ....4A and M.... on the others. transistors look right to me from this distance.

Most likely MP21A for all three, but yeah, the whole MP series has standard E-B-C triangle pinout.

I don't much like the look of that melt-hole in the 2n2 cap, though.

It's possible that it's a reflection of the solder lug in front of it - you can also see the white silkscreen reflected just to the right. I didn't think the cap would be shiny enough to reflect like that, but it seems like the most likely explanation.

[boris819]

Wow, so sorry for my lack of reply ! I've been doing some other things in the meanwhile !

So yeah, I don't think it's the transistors if, as said, one of the Q3s leg is supposed to be grounded, so muted.

The one thing I've got trouble explaining now, is that the 2n2j (c6) holes are reacting differently to my audio probe tests.. Even with no cap in place, I get a huge volume drop on the right hole vs the left one (left is the the one closer to c5). I thought it was c6 that was problematic, so I took it off, and of course, in my badluck, i broke the legs of it, so I need to buy another one 

Anyway, that rings any bell ?

So I think the problem is around the end of the circuit, where I circled it. But it's my newbie guess...



Also, I haven't played with the top half of the schema..

Thanks for all the attention you guys are giving me  

[idy]

You would expect, with no cap in C6 position to hear on the side close to Q3 a loud signal, and on the side close to the 10k to ground and the tone control, to hear very little. With the cap in place, you would expect to hear a thin, trebly sound there. With the tone control at full you should get a normal signal even without C6.

Oh, I think maybe when you say "close to" and "left" you are referring only to placement on PCB and aren't yet sure which end of the cap is which on the schematic; figure that out. Which side of the cap is going to the Q and which to the tone control? If there is no signal on the side that should be attached to Q3 then you have a broken trace.

Some PCB makers include in their docs a diagram of how the traces on the board go. This one doesn't and there is not way for us, just looking at the doc, to know which end is which.

[antonis]

Put ANY cap you have handy in place of C6 to verify Q3 good working mode..
(in case of electro cap, place its negative leg towards Q3 Collector..)

[boris819]

Okay so I just received the replacement Cap and installed it.

You would expect, with no cap in C6 position to hear on the side close to Q3 a loud signal, and on the side close to the 10k to ground and the tone control, to hear very little. With the cap in place, you would expect to hear a thin, trebly sound there. With the tone control at full you should get a normal signal even without C6.

You say that I should 'expect to hear a thin, trebly sound there. With the tone control at full you should get a normal signal even without C6' but there's clearly a difference between both sides of the C6, although it seems to be less different than it was before (not sure, couldn't do a A/B test). And I wasn't able to effectively detect which leg was connected to Q3.

So here's the current situation, in my simple words : following (from what I can) the schema and your comments with my audio probe, everything seems correct until around the circled part (see image). Q3 seems to be working as intended (from your comments). C5 and C6 should be fine too, if the fact that one of the sides of C6 is supposed to be kind of quiet. then, the tone pot looks to be at normal volume and affects the tone of the audio. after that, going on R10 and the level pot, everything is super quiet, and I think it's about there I lose most of my signal. Any ideas ? And just now realized that I might have some signal loss around R9 because the sound there is considerably quieter than around the Q3.




Also, should I investigate the higher half of the schema ? (the TC1033SCPA part)

Thanks for all the help guys ! Really appreciate it ! It makes it way more less 'not fun' to know we got a huge community out there to help.

[idy]

Do you have a multi-meter? The continuity test will show which side of c6 is attached to the Q3, but you should be able to see the traces on the board! Use the eyes.

You would want to check for shorts with the ohm setting on the meter. It seems like something is up with the 220k or the volume pot. You would check for proper values for r9 and 10, which you can do without removing them; The values you read should be close to 10k for r9 and less than 100k for r10 because parallel paths... the output (wiper of volume pot) should read over 60k when the volume is at max, and 0 when at minimum.

[duck_arse]

measure resistances to ground, please, and note your answers here. from both sides of C5. from both sides of C6. from the junction of R10 and level pot. please.

still this. do the measures, tell the results. it will proove/disprove the resistances in that area. look on the circuit diagram for hints to the correct readings.

don't worry about the higher half of the schema, it won't be affecting the audio.