Newcomb pathfinder PA into guitar amp

[getonemaker]

Hi everyone!

A friend of mine just found this beautiful Newcomb Pathfinder 40W PA amp.

What mods would you suggest to make it a nice guitar amp?

Mod the input for the 12ax7 with 33k in line and 1 M to the ground?

Remove the 180K feedback resistor?

Add a cathode bypass cap on the 7199?

Wire the two halves of the 12ax7 in series for gain control?

Thanks!

 

[boobtube]

It really depends what you want the amp to do. The input 12ax7 is grid leak biased. Generally this generates more distortion, although they have used 10 meg resistors. This will generate a little more voltage than the usual 2.2 or 3.3 meg value so it will be biased a little closer to center than the lower values.
The output section is wired for ultra linear operation, so it will be cleaner than the traditional way. EL84s distort nicely, so if you want power amp grind, this won't get it done like the traditional way. You could change the NFB resistor. This is a neat way to mod the amp for different sounds. The 180k value isn't allowing a lot of NFB, so removing it might not change a lot. Try it and see.
Maybe you could define a little better what you want the amp to do, cleaner or amp generated distortion.

 

[getonemaker]

Thanks for the reply. He is happy with it as is, especially with a TubeScreamer pedal, if needed. No mods then.