BOSS TU-2 high pitch frequency noise

[miltown]

I have a Boss TU-2 that puts out a high pitched noise , not a buzz but more of a ring . It doesn't matter if it is off or on , plugged into bypass or output. That all makes me think it's the power section of the circuit , but not totally sure about that . Luckily the board has workable components on it that have part numbers you can see. I have rang out all the electrolytic caps and they come up good when in circuit. Looking for some ideas on how to proceed to troubleshoot this . Thanks.

[Jazz P Bass]

Here is the SM.

[miltown]

Thanks this will be a tremendous help.

[Jazz P Bass]

Are you using a power pack?
If so, try a battery.

[Helmholtz]

Do you get the noise when powered from a battery?

JPB beat me.

I have rang out all the electrolytic caps and they come up good when in circuit.

What does this mean? How did you test the caps?

Does the tuner work fine apart from the noise?

[miltown]

Yes get the noise with a battery. ESR tester .

[Helmholtz]

Does the ESR tester also measure capacitance?

[miltown]

No does not measure capacitance just ohms. Tuner does work .Sorry forgot that part.

[Helmholtz]

No does not measure capacitance just ohms.

Well even a shorted cap would show very low ESR.

[miltown]

Yep that's why I tested them out.

[Helmholtz]

Yep that's why I tested them out.

Same with a cap that has developed an internal short or excessive leakage.

What I mean is that low ESR doesn't necessarily means a good cap.

For proper function a cap needs to have sufficient capacitance, low ESR and low leakage.

[nickb]

I suggest that you removed R6 temporarily. If this stop the noise then you know that it's coming from the digital section. Assuming that it is, you need to figure how.

C5 is an obvious suspect. I know you checked it but sometimes it's easier to just to replace, or at least tack another in parallel. Other routes much be poor grounding of jack sockets to case.

[nickb]

Let me say that again as I don't have the ability to edit the auto corrections that generate nonsense.

I suggest that you removed R6 temporarily. If this stop the noise then you know that it's coming from the digital section. Assuming that it is, you need to figure how.

C5 is an obvious suspect. I know you checked it but sometimes it's easier just to replace, or at least tack another in parallel. Other routes such bas poor grounding e.g. of jack sockets to case.

[miltown]

Replaced C5 and no more ring. Thanks nickb and thanks Jazz P , appreciate it.