Intermittent problem with PAB

[JD0x0]

99% of tube amp issues are tube related, sorry it was your black plates man!

Lessoned learned... dont invest in NOS power tubes, but pre amp tubes are a different story unless youre paying $150+ per tube

[butwhatif]

I have seen this exact thing caused by a loose solder joint, check them under your magnifier, or resolder all---

[tubedogsmith]

99% of tube amp issues are tube related, sorry it was your black plates man!

Amen, I need to quit assuming that the tubes have already been checked. I just "assume" that's the first thing everyone checks. Glad you found it brads.

[brads]

I spoke too soon.

Changing the power tubes merely moved the note where the problem occurs one fret up the neck. I posted that the problem was solved because it wasn't happening where it did previously.

Same problem----slightly different frequency.

Now I'm thinking it is a bad solder joint.

[Structo]

Bummer on the black plates.

I lucked into a pair of used ones a while back.
Currently they reside in my D'Lite.

I never really believed the hype about them, mainly because I couldn't afford them!

But to my old ears, they are the best my amp has sounded.
Before these I had Winged=C= 6L6GC's in there and they are pretty good for new tubes.

I have only bought a handful of vintage preamp tubes before this and I have to say I wasn't bowled over by the difference.
Maybe it has a lot to do with the type of circuit you are putting them in.
I lucked into a bunch of Sylvania 12ax7 pulls from some organs and since I don't own a tester, my amps are my testers.

Some of them are Raytheon 12ax7's and the ones I have tried so far sound pretty good but nothing that jumps out at me.
So as far as my D'Lite 44 is concerned, I don't hear the dollar to tone ratio that would influence me spending big bucks for NOS or used tubes.
Heck, maybe I have a tin ear, but when I was younger I had a pretty good sense of pitch and could name the note when somebody pressed a key on a tuned piano.

[Wayne]

I spoke too soon.

Changing the power tubes merely moved the note where the problem occurs one fret up the neck. I posted that the problem was solved because it wasn't happening where it did previously.

Same problem----slightly different frequency.

Now I'm thinking it is a bad solder joint.

Have you re-tensioned your tube sockets?

W

[brads]

I spoke too soon.

Changing the power tubes merely moved the note where the problem occurs one fret up the neck. I posted that the problem was solved because it wasn't happening where it did previously.

Same problem----slightly different frequency.

Now I'm thinking it is a bad solder joint.

Have you re-tensioned your tube sockets?

W

Not yet. I'll give that a try as well.

[ER]

Do you have covers on the pre-amp tubes? I had a similar problem and it was the springs in the tube covers...

-E

[brads]

Do you have covers on the pre-amp tubes? I had a similar problem and it was the springs in the tube covers...

-E

Will try that as well. Thanks!

[gazza]

I have "saved" several rca bp tubes with varies problems (including no filament) by resoldering the pins on the tubes.