[sdiy] Help trouble shooting noisy circuit

[David G Dixon]

Hey Joe,

Here's what I'd do:

Drop a 100pF ceramic capacitor across the "Negative In" and "Out" pins of
the TL072 that is oscillating.  That oughta fix it.

Cheers,
Doc Sketchy

-----Original Message-----
From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Joe
Frey
Sent: Sunday, January 12, 2025 3:04 PM
To: synth-diy at synth-diy.org
Subject: [sdiy] Help trouble shooting noisy circuit

[CAUTION: Non-UBC Email]

Hello, more than a decade ago I built with Harry Bissell's help a pitch 
to voltage circuit and an envelope follower and then built some 
supporting boards: power supply and two invert-offset circuits. One of 
the invert-offset boards is not functioning properly. It is a photo 
etched circuit board unlike it's brother that was made on strip-board. 
The invert and offset functions work properly but the output has a high 
frequency wave in it whether there is an input voltage or not. The 
brother circuit on strip-board works fine. Same power source for both. I 
have checked the component values(there are only resistors), checked all 
the traces with the circuit on paper, re-flowed all the solder joints 
and replaced the TL072  with others. I still have the issue. What should 
I look at next?

Is it possible that a faulty IC socket could produce this effect? I 
didn't change the socket because this basement darkroom circuit board I 
made then seems pretty fragile.

Thanks for any help. JoeF.


________________________________________________________
This is the Synth-diy mailing list
Submit email to: Synth-diy at synth-diy.org
View archive at: https://synth-diy.org/pipermail/synth-diy/
Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
Selling or trading? Use marketplace at synth-diy.org