Scratching My Head! Aion Fx Aurum

ReverendoRyan

ReverendoRyan

New member
Hey Guys, it's been a while!

I was wondering if I could get a fresh set of eyes on the problem I'm encountering.?

Building an Aion Aurum (boss OD-2). I've always has sound going through, but the drive knob does absolutely nothing. Mind you this is a with with a few (5) SMD's, and though i thought i did a good job, not a lot of experience so my mind immediately went to that. Now, at this point, the drive knob does nothing, but the sound is overdriven, just no adjustment possible.

The 2SK209's are intended to replace the original's 2SK117, which I managed to source. Popped out the SMD's, plugged those in. Now I have the drive knob that still doesn't work, and the sound is no longer overdrived.

I probed the circut, and without surprise, I'm getting input, it follows the circuit, once it passes the drive potentiometer I'm getting driven signal that seems to be affected by the drive knob (I test with an EHX RTG to keep hands free), but between Q5 and Q6 the signal drops and is just clean.

Before I keep going and risk miffing it up, I thought I'd tap into the collective intelligence. Anybody see something that jumps out?

Here's the board wired up :

1000006989.jpg

As you can see, Q6 gave my a bit of trouble yanking out the smd, the discoloration is burnt flux, I checked continuity on the pad with my multimeter, we're all good.

Other side of the board :

1000006997.jpg

1000006998.jpg

Here's the layout :

Sans titre.png

And the schematic :

schem.png

Now i've checked all the pinouts for the transistors, the values for the resistors etc from the beginning up to around the area causing problems. Anybody see something I've missed?

Thanks for your help!

Ryan
 
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Are you sure your transistors are installed in the correct holes on the PCB and in the correct orientation? I know that Aion provides extra connection points to accommodate different transistor configurations. A number of your transistors appear in the alternate locations which I don’t think should be the case if you’re using the part listed on the BOM
 
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I spent some time making sure everything was oriented the right way according to the pinouts, but as usual, if someone asks I begin to doubt myself! Here are the datasheets :

Q1-2-3-5-6 are 2SK117
Q4-7-9 are 2N3906
Q8-10-11-12 are 2N5088



2N3906.png 2n5088.png 2sk117.png

Though the 2SK117 datasheet I found is a little unclear to my liking on second glance. I searched for another pinout and found this, confirmed by a few others :

2SK117-Pinout.jpg

Which would mean i need to flip them 180° on my board. I'm gonna try that and get back to you!
 
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I think you're right. I looked at the build doc quickly, so might be missing something, but it says if you're using 2SK117s then you need to 'flip' them and shift them over. Your pic looks like they're not flipped.
 
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ReverendoRyan said:
I spent some time making sure everything was oriented the right way according to the pinouts, but as usual, if someone asks I begin to doubt myself! Here are the datasheets :

Q1-2-3-5-6 are 2SK117
Q4-7-9 are 2N3906
Q8-10-11-12 are 2N5088



View attachment 110216View attachment 110217View attachment 110218

Though the 2SK117 datasheet I found is a little unclear to my liking on second glance. I searched for another pinout and found this, confirmed by a few others :

View attachment 110219

Which would mean i need to flip them 180° on my board. I'm gonna try that and get back to you!
Click to expand...
The pinout for the 2SK117 looks the same in those two sources to me. Drain is leftmost looking at it from the flat side. Besides, FET’s drain and source are usually interchangeable.
 
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giovanni said:
The pinout for the 2SK117 looks the same in those two sources to me. Drain is leftmost looking at it from the flat side. Besides, FET’s drain and source are usually interchangeable.
Click to expand...
I couldn’t verify whether it is actually symmetrical so if you have it oriented backwards it may be good to try flipping it. But it may not solve your issue.
 
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Ok, probed a bit to locate where the hiss begins :

hiss begins.png

Hiss becomes noticable coming out of C4 (nothing on R8), but you have to crank amp volume to hear it

At this stage :

really amplified.png
Things get really noticable coming out of C9 at any volume, and is influenced by the drive knob
 
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The values of the components around that section look correct, but your C8 looks lightly melted. I think that cap is acting as a low pass filter and if it’s not working properly it might be letting more high end hiss into the signal. It doesn’t look too badly singed (I’ve certainly done worse to a cap and had it work fine), but it’s something to check.
 
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Maybe check c4? It might have overheated something or you bumped a lead and it broke? Not likely, but another place to look.

It might not hurt to reflow the connections after Q3 up to the drive pot. One side of the c4 solder joint looks a bit skimpy on the solder
 
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Welp, I'm sorry to say that this has been ANOTHER SUCCESS for the community!

So I changed C8, C9 and C4, and reflowed all the connections, and we have got a live one!

Thanks to everyone who helped. It's been a while since I needed a fresh set of eyes, and it's so refreshing to see that this forum is still as strong and friendly.

Thanks again!
 
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