SOLVED Blue Sheep No Effect

[joelorigo]

I'm testing my in-progress Blue Sheep in my Auditorium Test Platform, I am getting a bypass signal, but when switching to Active, there is a "pop" but then no signal. I have continuity between the Test Platform and the PCB on all the connections, I don't see any solder bridges and the Platform was working earlier when I tested another circuit. Can someone take a look?

 

[joelorigo]

No, that is a troubleshooting item I have never heard of or had to do yet. Like a chopstick/pencil? While it is plugged in an activated?

 

[music6000]

No, that is a troubleshooting item I have never heard of or had to do yet. Like a chopstick/pencil? While it is plugged in an activated?

Yes.

 

[joelorigo]

I plugged it in and hear the hum sound when activated. Then used a wooden chop stick to poke/prod/wiggle the 2 100u caps.
Nothing changed.
Then I got out the audio probe again, just to see if this pattern repeats and it did. At the beginning of the probing the hum was at the OUT, but going back and probing various points I was able to follow the signal path to the OUT. So, leaving it plugged in, it is currently it is working from going to bypass to activated as one would hope.

 

[zgrav]

try reflowing the solder connections for all of the capacitors on the PCB.

 

[joelorigo]

try reflowing the solder connections for all of the capacitors on the PCB.

I sure can. Would you still suggest that if I said I have already reflowed every solder spot already?

 

[zgrav]

When you check with the audio probe, have you tried starting at the output to see if you hear the hum then? If so, working backwards to the point where the hum stops might help you isolate the problem.

Given the intermittent results with the audio probe, I think the issue is a connection with a capacitor. Reflowing the connections again is easy enough to do and test. If that does not stop the issue I would then replace the two largest caps on the board, but check after just replacing the first one just in case that fixes the problem.

 

[joelorigo]

When you check with the audio probe, have you tried starting at the output to see if you hear the hum then? If so, working backwards to the point where the hum stops might help you isolate the problem.

No, once I have the signal at IN and hum and OUT, I have always started going from the IN and following the schematic forward. I see your point though!

Given the intermittent results with the audio probe, I think the issue is a connection with a capacitor. Reflowing the connections again is easy enough to do and test. If that does not stop the issue I would then replace the two largest caps on the board, but check after just replacing the first one just in case that fixes the problem.

OK, totally, thank you.

 

[joelorigo]

Just to confirm again, I tired it after leaving it plugged in for a while, it worked, unplugged it and it didn't work (hum). Then I started probing again but working backward. Hum is coming out of IC 2 pin 7, but got signal going in to IC 2 pin 5 & 6. So if I am understanding this correctly, there is something happening in the lineage after leaving pin 6 from IC 2?

Then a leg of the capacitor on my DIY audio probe broke off. I currently don't have a box 100n that I used but I do have a MLCC of that value. Can I use that as a replacement?

 

[joelorigo]

I fixed the audio probe and got back at it. I verified that there was the hum at OUT and that there was still signal on IC 2 pin 5 & 6 but not 7. Then moved to the 2n2 cap and the 10k resistor, I got signal on one side and the hum on the other. Then I started in on the 33n caps, and both sides of the 33n caps had signal and so did all 4k7 resistor. I went back to the 2n2 cap and the 10k resistor and I now got signal on both sides. Now I should note that there may been some "pop" sound at some point in the probing of the 33n caps and 4k7 resistor.

Is the fact that, when it wasn't working, there was signal at IC 2 pin 6 and not 7 mean that the problem I am having is in that section? Or could it still be something in the power section

 

[Laundryroom David]

I’m stumped! Do you have more boards? Maybe just do a fresh build?

 

[music6000]

I fixed the audio probe and got back at it. I verified that there was the hum at OUT and that there was still signal on IC 2 pin 5 & 6 but not 7. Then moved to the 2n2 cap and the 10k resistor, I got signal on one side and the hum on the other. Then I started in on the 33n caps, and both sides of the 33n caps had signal and so did all 4k7 resistor. I went back to the 2n2 cap and the 10k resistor and I now got signal on both sides. Now I should note that there may been some "pop" sound at some point in the probing of the 33n caps and 4k7 resistor.

Is the fact that, when it wasn't working, there was signal at IC 2 pin 6 and not 7 mean that the problem I am having is in that section? Or could it still be something in the power section

Have you tried doing the same thing to the 33nF Caps as I suggested before, Chop Stick time again!

 

[joelorigo]

I’m stumped! Do you have more boards? Maybe just do a fresh build?

I've stumped the experts! I do have another PCB and I have been thinking about writing this one off and trying another build.

 

[joelorigo]

Have you tried doing the same thing to the 33nF Caps as I suggested before, Chop Stick time again!

I will do it! And I will reflow the caps again as suggested above.

 

[Laundryroom David]

That’s a

Have you tried doing the same thing to the 33nF Caps as I suggested before, Chop Stick time again!

That’s a great idea - agreed

 

[Laundryroom David]

I've stumped the experts! I do have another PCB and I have been thinking about writing this one off and trying another build.

Check those 33n caps for sure. I missed it.

 

[joelorigo]

After the last above posts I got really busy and didn't have time for building for a while. Rather than continue with this troubleshooting, I decided to start from scratch on duplicate PCB I had, which was a suggestion somewhere in this long thread. Built it today and it makes the same buzzy noise. Is it possible I got a bad batch of PCBs, or that I did something wrong when I ordered them from JLCPCB??

 

[szukalski]

Without having been through the whole thread, I can’t see you doing anything wrong when ordering from JLC (there’s not much to do wrong).

I’d say, get an audio probe and trace the schematic to see where things get fuzzy.

 

[joelorigo]

Oh, one more thought, this is the first time I have used one of these 3DPT breakout boards. Does anything look wrong there?

 

[joelorigo]

Without having been through the whole thread, I can’t see you doing anything wrong when ordering from JLC (there’s not much to do wrong).

I’d say, get an audio probe and trace the schematic to see where things get fuzzy.

I guess I’d be curious to see if probing it gives the same results as the first one. But there’s got to be something weird going on here since 2 of them have the same issue.

 

[joelorigo]

I searched "blue sheep" on this forum and found a thread where @Laundryroom David was reporting bad TL072 chips that he had received. Coincidently, it was in a Blue Sheep where he realized this. He tried a couple NE5532s and his worked. And it does for me. Yay!

But...

I am 99.9999999999% certain that the 2 TL072 chips I have been using, and a few others I rotated in the beginning of this thread, I tried individually in a Mahayana that I was simultaneously building with my first attempt, and had no problem. Huh? Gah!