Trying to do a fix in the lowest number of focused steps, if possible. Here's the patient: New Princeton Reverb build (Hoffman circuit, not my first). Everything sounds really good, except for what sounds like "ringing" noise on G string, notes B and C (3rd and 4th fret). Doesn't happen with any other notes afaict. Doesn't do this with same guitar on a very nearly identical amp, same guitar settings and amp settings. Reverb cables unplugged and verb switched off, no difference. Trem circuit switched off, no difference. Treble and bass dialed up and down, no difference. Occurs on input 1 and input 2. Swapped out all tubes from the "good amp", no difference. Bias settings are super-close between the two amps. Speaker is new, Canabis Rex 12. Have not tried a different speaker but have a few spares of different types. So I'm thinking this is a lead dress thing that I should look at first. My plan is to yank the chassis, get it up on blocks, inject an "offending" signal with a sig gen, and scope that from the speaker-out. Hopefully I will see something in the waveform at the offending freq that shows a squirrelly waveform. If so I'll then chopstick the wires attached to V1. Would you do something else first?