"Ghost" notes in my Silverface Twin..??..

[JingleJungle]

I just had an acquaintance over to try out one of my guitties for sale.
We plugged into my early 80s Fender Silverface Twin (Mastervolume) and off we went - volume on 4, all tones on 5, reverb on 3, master on 3.

My friend was basically looking for dead spots on the fretboard when we both heard that the E on the g string (9th) fret produced a ghost note.
It seems to be off like about a semitone or so. It gets fainter on F and Eb. we tried some other guitars and yup, the note is always there.
I can hear it in the dry channel (faintly) and in the vib-rev channel (more pronounced).

What is it? A microphonic pre tube? If so, which could it be?
There's an awful lot of pillbottles to swap around there, so I'd appreciate if someone could give me a pointer as to where to start looking.

Thank y'all!!

JJ

 

[tmac]

Could be a preamp tube giving off some sympathetic microphonics, or maybe speaker cone cry.

Could be power supply filter caps too. When they get dry they can lend an odd hamonic under a note.

 

[JingleJungle]

Originally posted by tmac
Could be a preamp tube giving off some sympathetic microphonics, or maybe speaker cone cry.

Could be power supply filter caps too. When they get dry they can lend an odd hamonic under a note.

Would one get cone speaker cry even at low volumes?
OTOH the idea of the caps seems "interesting" (in a bad way, unfortunately).

Thank you,

JJ

 

[TheAmpNerd]

Originally posted by JingleJungle
OTOH the idea of the caps seems "interesting" (in a bad way, unfortunately).

Shouldn't be bad at all.

tmac is on the correct path.

Then eliminate possibilities...

1. Does it do the same thing in both channels?

If yes, then
probably down stream
Check PI and power tubes.

If not, then
it is either V2 , V3, V4,
Replace one at a time until
found.


If that doesn't work, plug the amp
into another cab see if that does it.

Also tighten up the baffle board,
and speakers, just in case.

If non of that works could be time
for a cap job...it is about due, if the
amp is an 80s Twin.

Good luck and let us know what you find out.

There are a bunch of great folks who hang out here.

 

[Blue Strat]

Originally posted by JingleJungle
Would one get cone speaker cry even at low volumes?
OTOH the idea of the caps seems "interesting" (in a bad way, unfortunately).

Thank you,

JJ

Caps would be my first guess. Try disconnecting one speaker at a time and see what happens.

 

[John Phillips]

Remember that in Europe, mains frequency is 50Hz, which is very close to a G.

A failing filter cap could cause this sort of following note. If the caps are original, I'd start there. This is quite a normal symptom.

 

[JingleJungle]

Thank you guys. Your info is invaluable!

Just to give you an idea of the scale of the problem

There are no "amp doctors" where I live
The closest amp specialist is 45 minutes away
In august everyting shuts down for a month or so



Major bummer - esepcially if you think that my Rivera M60 is still dead (there still is a post somewhere to this effect).

JJ

 

[John Phillips]

Originally posted by JingleJungle
Major bummer - esepcially if you think that my Rivera M60 is still dead (there still is a post somewhere to this effect).

I must have missed that one... I've just posted a suggestion on it.

 

[JingleJungle]

Dude - you're great.
Thank you so much.

JJ

 

[Wakarusa]

One other place to look is the guitar itself. If the strings are too close to the pickups you can get ghost noting.