Blues Jr (Cream Board) Overdriving

[Michael Smith]

Looks like a dirty signal. Do you get the same thing on the middle and bass pots? What about on the volume pot? EL34World has a pdf of the Blues Jr. Service manual showing all of the test points, component values, etc.

 

[2L man]

Compare signal on other places. When you use probe 10:1 it is safe to look anode signal. If it is distorted then look control grid signal.

 

[Pete Farrington]

Can you provide a link to the relevant schematic? They have lots of info that can be helpful with fault finding.

 

[ReconbradEPTX]

Here’s a link to the schematic:
https://ampwares.com/schematics/bluesjuniorIII-rev-b.pdf

As for probing results on the other locations, it’s only found on that location. Seems weird but I tested another blues Jr with the same board and it looks the same on the scope at that same location.