Phase II- weird issue

[Pauleo1214]

This one is frustrating since I wired one of these up and it worked on first fire up.

I get signal and modulation if I wave my finger over the lfo led and ldr resistors. The problem is the led is constantly lit and does not fluctuate with the rate.

I already corrected some value errors for resistors (6.8k instead of 68k). Can anybody with eagle eyes spot anything else wrong or might know why their is no rate?

 

[Coda]

Have you played around with the trimmers at all?

 

[zgrav]

make sure your transistor is getting a good connection at the socket. have you checked voltages for the IC?

 

[Pauleo1214]

Have you played around with the trimmers at all?

Yes, no effect besides swimming the led and overall gain.

make sure your transistor is getting a good connection at the socket. have you checked voltages for the IC?

Haven't checked voltages yet but figure it may be another issue if modulation occurs when i wave my finger over the ldrs.

 

[zgrav]

Yes, no effect besides swimming the led and overall gain.

Haven't checked voltages yet but figure it may be another issue if modulation occurs when i wave my finger over the ldrs.

The problem is that your LFO is not working in the circuit. The audio path is likely OK, which is why varying the light hitting the LDRs will change the sound. That means an audio probe won't be a lot of help, so you will be using your DMM to check connections and voltages on the transistor and ICs. You already know your led works, but need to figure out why it is not cycling.

 

[Pauleo1214]

The problem is that your LFO is not working in the circuit. The audio path is likely OK, which is why varying the light hitting the LDRs will change the sound. That means an audio probe won't be a lot of help, so you will be using your DMM to check connections and voltages on the transistor and ICs. You already know your led works, but need to figure out why it is not cycling.

So all the ICs are getting voltage. 8.5V for pin 8 of all the TL072s. The LED dims when I measure pin 3 of IC 6. i get 8.5v on pin 3 of the 4401 transistor and the TC1044.

 

[zgrav]

are you getting any voltages higher than 8.5 on your 1044? you should be getting 8
check the solder connections for your trim pots. when you adjust the trim pots does it change the brightness of the LED?

 

[Pauleo1214]

are you getting any voltages higher than 8.5 on your 1044? you should be getting 8
check the solder connections for your trim pots. when you adjust the trim pots does it change the brightness of the LED

Thank you for your continued help.

8.48V on leg 8 of the 1044. Turning the trimpots does adjust the brightness of the LED. I am pretty certain all my resistor values are correct and I reflowed my solder joints three times over.

 

[Pauleo1214]

are you getting any voltages higher than 8.5 on your 1044? you should be getting 8
check the solder connections for your trim pots. when you adjust the trim pots does it change the brightness of the LED?

Don't kill me. I started replacing iCs and looks like IC6 was bad? The LED is cycling now! I'm sorry for the fuss and appreciate your help @zgrav !

 

[zgrav]

Don't kill me. I started replacing iCs and looks like IC6 was bad? The LED is cycling now! I'm sorry for the fuss and appreciate your help @zgrav !

Glad you got it sorted out!