Mesa MKIIB -RP-9C

[Jamme1961]

thanks for any help on this - its a 1982 RP-9C circuit board (SRG) Serial # 8751. Lead channel is not switching right? IF i use the pull pot to switch to lead, it engages the normal and the lead master pots? when I use the footswitch it seems to work - I can see and hear the relay working can it still be that? Thanks for any ideas what I can check - I did replace all main Filter caps with what I had because originals were leaking- see pics

 

[Jamme1961]

also anyone recommend a good Mesa Boogie tech in Northern NJ area? anyone use
https://fuchsaudiotechnology.com/ ? thxs again for any help on this stuff

 

[Jay Omega]

thanks for any help on this - its a 1982 RP-9C circuit board (SRG) Serial # 8751. Lead channel is not switching right? IF i use the pull pot to switch to lead, it engages the normal and the lead master pots? when I use the footswitch it seems to work - the light is off for lead and on for rhythm channel- I can see and hear the relay working can it still be that? Thanks for any ideas what I can check - I did replace all main Filter caps with what I had because originals were leaking- see pics

What do you mean by it's not switching right? The behavior you described sounds appropriate. Master 1 is active in both rhythm and lead modes, Lead Master should only be active in the lead mode.

 

[Jamme1961]

I thought master 1 is for rhythm channel only? When I use the pull pot to engage the lead channel it is still active along with the lead master? Just getting started not a lot of time - I realize this is a PIA to diagnose through my words - thanks again for any help

 

[Jamme1961]

well since you straightened me out on the master volume- it seems to be working fine. I cleaned out the tube sockets again and noise is gone - thanks for the help I appreciate it.

 

[edge59AlnicoIV]

I thought master 1 is for rhythm channel only? When I use the pull pot to engage the lead channel it is still active along with the lead master? Just getting started not a lot of time - I realize this is a PIA to diagnose through my words - thanks again for any help

The master is actually a global master, you can run you lead channel master higher to smooth out the tone and lower the Master (global). Does that make sense?

 

[edge59AlnicoIV]

The master is actually a global master, you can run you lead channel master higher to smooth out the tone and lower the Master (global). Does that make sense?

At least it works for me, sometimes run a quality compressor in the loop like Trey Anastasia from Phish does with his Mark III

 

[edge59AlnicoIV]

At least it works for me, sometimes run a quality compressor in the loop like Trey Anastasia from Phish does with his Mark III

I find lower settings if the master can sound a bit fizzy, even a volume pedal in the loop helps me, having Ross style similar (Jackson Audio Bloom is an awesome comp) comp in the loop can be dialed in so that it smooths out the lead tones like the amp sounds when the volumes are pushed with great sustain at lower volumes, and rolling back the guitars volume cleans up nice, keeping clean headroom... Just my experience ....

 

[edge59AlnicoIV]

also anyone recommend a good Mesa Boogie tech in Northern NJ area? anyone use
https://fuchsaudiotechnology.com/ ? thxs again for any help on this stuff

Check with Andy Fuch's he has worked on these and has some great upgrades for them if he still works on them. Tell him Ed Goforth sent you

 

[Jamme1961]

Thanks he worked on a Rivera I had forgot about him thanks

 

[edge59AlnicoIV]

Thanks he worked on a Rivera I had forgot about him thanks

 

[edge59AlnicoIV]

thanks for any help on this - its a 1982 RP-9C circuit board (SRG) Serial # 8751. Lead channel is not switching right? IF i use the pull pot to switch to lead, it engages the normal and the lead master pots? when I use the footswitch it seems to work - I can see and hear the relay working can it still be that? Thanks for any ideas what I can check - I did replace all main Filter caps with what I had because originals were leaking- see pics

Look at the pic you posted, someone re-routed the cathode bypass cap!

 

[edge59AlnicoIV]

Look at the pic you posted, someone re-routed the cathode bypass cap!

 

[Jamme1961]

wow you think someone did that? have you seen others wired like that? it doesn't make sense- the pot ground wire is there?
see below for pictures I found online totally confused now - crazy

 

[Jamme1961]

 

[Jamme1961]

I just found this picture online showing what your saying - so now I have to figure out the values of the cathode cap and it also looks like there's a resistor where my amp has the .01 orange cap -I may have to bring this to Fuchs - it looks like there's a resistor moved (next to the big black 100K plate resistor) and the other big orange drop cap looks like its been moved - someone reworked this part of the circuit. Or maybe this is a picture of a mod? no way to tell what's going on here - I also found this picture which shows an circuit more like mine see below -confused?