[sdiy] Help trouble shooting noisy circuit

[Ben Stuyts]

If you’ve replaced the op-amp, any dirty contacts in the ic-socket will have been wiped clean, more or less. But it could never hurt to measure resistance between the pins of the op-amp and the bottom of the pcb. If there’s any contact resistance or broken pins it should show up.

You mention the PCB is pretty fragile. Maybe there is a hairline break in one of the traces. I’d measure all connections, from component pin to component pin.

Is the power supply of the op-amp properly decoupled?

Ben

> On 13 Jan 2025, at 00:03, Joe Frey <frey at radioles.com> wrote:
> 
> 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.
> 
> 
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