# ADHD Low Output



## andrewcx13 (Apr 4, 2021)

So I have this one where the effect works, the light turns on when engaged, and I can hear the distortion on the signal. My only issue is that the output is incredibly low . I have a fulltone v2 and it's immensely louder, so I know something here is wrong on my end. 

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I built an audio probe this morning, I just have no idea what I'm doing with it in regards to troubleshooting in this situation.


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## giovanni (Apr 4, 2021)

I would start by checking some nodes with an audio probe. We can start by checking each output of each stage. That means: at the drain of Q5 (where it connects with R27); at pins 1 and 7 of the IC. You should hear increasingly louder signal.


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## andrewcx13 (Apr 4, 2021)

This is exactly the type of guidance I was looking for. I just hit my noise curfew, so it'll have to wait until tomorrow, but thank you for the tip. Next chance I get with the iron I'll hook this up and see what I find and report back.


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## PJS (Apr 5, 2021)

With this circuit it also helps to know which mode gives low output.  You have true bypass vs buffered bypass, and then effect bypassed and engaged.  If you are getting normal output with it bypassed in both modes, and only getting low volume with the effect engaged, then the problem is likely in the effect part of the circuit.  If you get low volume with everything except true bypass and bypassed then the problem is likely in the buffer.


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## andrewcx13 (Apr 6, 2021)

Ok, got the ADHD back on the testing rig. 

So the output doesn't change level when either of the switches are flipped

Got the audio probe working and was able to hear the same low level signal on the drain of Q5. On Pin 1 and 7 I have no output at all.


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## Chuck D. Bones (Apr 6, 2021)

Remove all of the flux residue with alcohol and a tooth brush, then visually inspect all of the solder joints.  Have you double-checked all of the component values?  Have you subbed any parts, or do all of the part numbers & values match the BOM?  Where did you get your JFETs (Q5 & Q6)?

Once you have done all of that, measure these voltages:
IC1 pins 1, 7 & 8.
Q4 collector.
Q5 and Q6 drain.


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## PJS (Apr 6, 2021)

I recently got one running that had similar symptoms.  I had actually not soldered one leg of Q6.  It was touching the plating in the hole enough to let some signal through, but not well.  Your problem will be something simple like that as well I think.  Poor solder or a wrong component.


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## andrewcx13 (Apr 7, 2021)

cleaned the board, reflowed all the solder joints, checked all the caps (I need to still check the resistors), did not sub out any parts on this build. All components from small bear/tayda/mouser.

Q5 drain - .22v DC
Q6 drain - 17.34v DC
Q4 collector - 0v DC
IC1 Pin 1 - 8.78v DC
IC1 Pin 7 - 8.79v DC
IC1 Pin 8 - 17.6v DC


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## Chuck D. Bones (Apr 7, 2021)

andrewcx13 said:


> cleaned the board, reflowed all the solder joints, checked all the caps (I need to still check the resistors), did not sub out any parts on this build. All components from small bear/tayda/mouser.
> 
> Q5 drain - .22v DC   Seems a bit low.  I forgot Q5 is upside down on the schematic.  Check Q5-S.
> Q6 drain - 17.34v DC  *This is way too high. * Check Q6-S.
> ...



Are you running this on 18V?  What are the voltage ratings on C11 & C12?  If you're going to color outside the lines, you need to tell us.


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## andrewcx13 (Apr 8, 2021)

So I accidentally did run this at 18v. 

Though from what I understand, this can handle 18v, so that leads me to believe something is still wrong. 

I'm going to recheck voltages tomorrow with the correct voltage along with checking the solder joints you mentioned. Thank you Chuck.


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## Barry (Apr 8, 2021)

andrewcx13 said:


> So I accidentally did run this at 18v.
> 
> Though from what I understand, this can handle 18v, so that leads me to believe something is still wrong.
> 
> I'm going to recheck voltages tomorrow with the correct voltage along with checking the solder joints you mentioned. Thank you Chuck.


It can possibly handle 18v if you used the rated components for 18V, a lot of the electrolytic caps out there are rated at 16V


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