Ringing / rattling sound super imposed over guitar notes

[marshallguy]

Plugged the guitar also into FX return to isolate, ringing / rattling persists. Changed tubes, speaker cabinets, added dampers, problem persists.

Narrowed it down between FX return and output. Everything else works, sounds fine, just this annoying buzzy, rattling ringing on the chords, notes.

Thank you. 

[sluckey]

Maybe just a scope trigger problem. Exactly how are you triggering the scope?

[AlNewman]

You could measure voltages at the power tubes and phase inverter and share.

[PRR]

Putting any sort of probe on power tube plates is begging for trouble. Exploded probes, 'scopes, meters. And oscillations galore when the 400V AC audio radiates from the probe leads back to the sensitive preamp.

With the amp properly shielded--- are you really getting 1000Hz tones behind the music? That's an awful odd freq to happen accidentally.

[marshallguy]

 

[marshallguy]

You could measure voltages at the power tubes and phase inverter and share.

Hi,

Output tubes Plate V. 456v /456v

P.I. B+.  335v
82k plate. 178v
91k plate. 175v

[marshallguy]

With the amp properly shielded--- are you really getting 1000Hz tones behind the music? That's an awful odd freq to happen accidentally.
[/quote]


I can’t say for sure what freq tones I’m getting behind the music except to say it is present anywhere on the guitar neck which is strummed, picked or plucked.

[sluckey]

Maybe just a scope trigger problem. Exactly how are you triggering the scope?

Source - Ch. 1

Use a BNC "Tee" to run another cable directly from the signal source to the scope EXT TRIG input and set the scope to trigger on that rather than CH1. That will resolve any triggering issues and makes the trigger level independent of the signal at the probe.

[marshallguy]

Maybe just a scope trigger problem. Exactly how are you triggering the scope?

Source - Ch. 1

Use a BNC "Tee" to run another cable directly from the signal source to the scope EXT TRIG input and set the scope to trigger on that rather than CH1. That will resolve any triggering issues and makes the trigger level independent of the signal at the probe.

Thanks.

By the way,

Will this work with Global NFB?

https://cdnimages.opentip.com/Docs/CED/snubber_article_k-snub.pdf

[marshallguy]

Maybe just a scope trigger problem. Exactly how are you triggering the scope?

You nailed it.