RM50 tube layout

[ricky]

I have an RM50 I picked up and there is some occasional tube noise and I am not sure if it is a power tube or not. I know that each module has 2 12ax7s and my RM4 also has two 12ax7s. Does the RM50 have the other pair too? How does one know when they are bad vs. a power tube? I kind of ruled out the modules as three of them had the same noise, so I am assuming that it is something else. What does anyone think?

 

[Mike361]

Pretty sure there are 3 12ax7. The are 1 that drive the amp and 1 effects loop buffer and 1 phase inverter. Some guys put 12ay's in the phase inverter spot there is lots of info if you do a search here. Edited to correct info.

 

[jimosity]

The RM50 has three 12ax7 (or whatever) preamp tubes.
One for input buffer tube; then two tubes to buffer the effects loops.

.... and two power tubes.


<Not counting the two preamp tubes in the modules>

 

[Jaded Faith]

There are 3 12AX7's. V1 is closest to the guitar input jack and it's the first shared gain stage for all modules. V2 is in the middle and buffers the effects loop. V3 is the PI tube and it's right next to the power tubes.

 

[Mattfig]

And let's not forget to add a magical 5751 to V3 (nearest the power tubes) to maximize your tone.

 

[ricky]

Is there a tube running the reverb or is that the same as the effects loop tube? If I hear tube noise, I know that I can switch out modules and figure out if it is the module tubes or not. How do I figure out which of the other ones is bad?

 

[Mattfig]

Is there a tube running the reverb or is that the same as the effects loop tube? If I hear tube noise, I know that I can switch out modules and figure out if it is the module tubes or not. How do I figure out which of the other ones is bad?

You can swap a known good one in and out....Your parallel loop is tube buffered...That's why so many choose to use a jumper there for a boost....Or if a tube is going microphonic, you can try gently tapping each tube with a pencil and see if one is noisy....

 

[sfx70]

I have to try the 5751 in the PI!
Isn't V1 really on the MODULE itself not on the amp? That's what I thought according to some pps in RigTalk

 

[mrtatemyballs]

1/2 of V1 is in the amp, the other 1/2 of V1 is in the module from what I understand. The tube closest to the input jack on the amp is V1, the 2nd one is effects loop, and the one closest to the power tubes is the phase inverter.