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]

I have the audio probe out. I am getting signal up to the 3 leg of the IC. Nothing after that. I'm a novice at reading a schematic but shouldn't there be signal in the 2nd leg of the IC? Which then goes off to the 47p cap, 15k resistor, the lugs of the PRE pot, the 1.2k resistor and 220n cap?

 

[Laundryroom David]

I have the audio probe out. I am getting signal up to the 3 leg of the IC. Nothing after that. I'm a novice at reading a schematic but shouldn't there be signal in the 2nd leg of the IC? Which then goes off to the 47p cap, 15k resistor, the lugs of the PRE pot, the 1.2k resistor and 220n cap?

How about pin 1?

 

[joelorigo]

No nothing in 1

 

[Laundryroom David]

No nothing in 1

I’m not expecting anything, but do you get anything on IC2? Particularly at pin 3?

 

[joelorigo]

No, nothing on any of those pins

 

[jwin615]

Check ground and power continuity on 8 and 4(powered off) or just probe pin 4. Carefully. And ohm 8 to ground

 

[joelorigo]

Ah! Speaking of that, I cant remember because I've done this so infrequently, does the circuit need to be connected to power while probing? The results I have listed so far are unplugged from any power supply.

 

[jwin615]

For audio or power yes.
For continuity, no.

 

[joelorigo]

Check ground and power continuity on 8 and 4(powered off) or just probe pin 4. Carefully. And ohm 8 to ground

IC1 right? I get ground continuity on 4 and 8, no power continuity on either.

What does "ohm 8 to ground" mean?

 

[joelorigo]

Also, I have plugged in the Test Platform and I get the same results as above in posts #21, #23 & #25.

 

[jwin615]

Should have continuity/minimal ohms from pin 8 to ground.
Should have VCC(power) at 4.
Sorry, ohm in verb slang as in ohm out that connection, ohm that cable and make sure it's dead. General slang meaning to do something with your DMM. Also, "to check for resistance (ohms)"

 

[jwin615]

You're getting audio in, no audio out of your opamp. You tested the IC, so issue point to power.

 

[joelorigo]

So I should be getting continuity with IC 1 pin 4 and the power (the "+" on the test platform)? And I am not.

 

[jwin615]

I may have misspoke. Poor at multitasking.
Set your DMM to DC
Power on the board.

Black lead to ground(-) on test platform
Red lead to pin 8. Should read ~9vdc

If good, then go one lead pin 4, the other to 9v on the platform(+)
Should also be ~9v.

If the first test is bad, check you diode(1n5817) and it's orientation.
Also, the filter cap(100u electrolytic)

If the second test is bad, you've lost ground somewhere.

If both are bad, you have no potential between ground and 9v(VCC/vdc) and youve likely shorted 9v to ground. That goes back to the filter cap as well as solder shorts.

 

[joelorigo]

I may have misspoke. Poor at multitasking.
Set your DMM to DC
Power on the board.

Black lead to ground(-) on test platform
Red lead to pin 8. Should read ~9vdc

Yes, specifically 9.27

If good, then go one lead pin 4, the other to 9v on the platform(+)
Should also be ~9v.

Yes, specifically 9.51

If the first test is bad, check you diode(1n5817) and it's orientation.
Also, the filter cap(100u electrolytic)

If the second test is bad, you've lost ground somewhere.

If both are bad, you have no potential between ground and 9v(VCC/vdc) and youve likely shorted 9v to ground. That goes back to the filter cap as well as solder shorts.

So both are good, right?
I included a pic of the DMM setting to be sure it is correct.
I sure know about multitasking, I am doing it right now!

 

[jwin615]

Wait. When you tested for audio earlier, do you have power applied?

 

[joelorigo]

I didn't, but then plugged it in and got the same results.

 

[joelorigo]

Well, I took the weekend off from thinking about this, but now that it appears I have the correct readings on pin 4 & 8, where do I go from here?

 

[zgrav]

start looking at all connections that go to the IC. If you have power and ground at the right pins on the IC, and audio coming in, then figure out why there is no audio coming out.

Is the output pin on the IC shorting out to ground or to another part of the board?

Gently remove the IC from the socket and bend the audio output pin so it does not fit into the socket when you put it back in.
Then power up the circuit and use your audio probe to see if you are getting audio output on the pin you kept from going back in the socket. If you have audio on the pin, but not when the pin is in the socket, you check the parts that connect to that pin on the PCB to isolate where the audio is being blocked/shorted to ground.

 

[szukalski]

You can also test for connectivity between parts. Disconnect the pcb from power, then try testing between various points.

A great start would be between power and ground , to make sure there’s no short circuit anywhere.