Mesa JP2C speaker on/off toggle issue.

[jasonP]

Hey Guys, I was wondering if any of you had this issue before with your JP2C. I don't ever record silently however I use the speaker on/off toggle sometimes to mute the output as the amp has a resistor for speaker load. What is interesting is this last weekend, I turned the amp on and the speaker toggle was set to off and I was getting a crazy oscillation, ringing like a bad microphonic pre-amp tube on the 2 gain channels. Volume doesn't change while going from speaker on to off, just goes into oscillation while the toggle is set to off. Checked all the tubes but that doesn't explain why the amp would just sit and oscillate and have full volume coming through the speaker cabinet. I checked the resistor which is good and check the toggle and seems to be working and turning on the resistor. I'm just not sure what else the switch is doing because it has that bullshit cab clone DI output and with no schematic is makes it hard to figure out what is going on. I sent Mesa Boogie a email for tech support. Will see how this plays out.

 

[brunocormack]

Man, definitely be careful troubleshooting that one. Since the JP-2C engages an internal dummy load when that switch is set to 'Off', any intermittent connection or dead spot inside the toggle could leave the power section without a proper load if a speaker cabinet isn't plugged in, or vice-versa.

Is it completely cutting the signal to the cabinet, or are you just getting a massive volume drop/popping sound when you flip it? If the switch feels physically mushy, Mesa customer service is usually great about shipping out replacement exact-spec Carling or E-Switch toggles.

 

[jasonP]

Man, definitely be careful troubleshooting that one. Since the JP-2C engages an internal dummy load when that switch is set to 'Off', any intermittent connection or dead spot inside the toggle could leave the power section without a proper load if a speaker cabinet isn't plugged in, or vice-versa.

Is it completely cutting the signal to the cabinet, or are you just getting a massive volume drop/popping sound when you flip it? If the switch feels physically mushy, Mesa customer service is usually great about shipping out replacement exact-spec Carling or E-Switch toggles.

I don't play without a speaker load just typically set the speaker on/off switch to off when I turn the amp off as a habit just in case I forget to plug a speaker into the amp when I'm moving amps around.
When having the speaker on/off switch set to off, I'm not getting a massive volume drop. I measured the 100 watt, 10R resistor and can see that the toggle switch is working and measures good. The PI feedback loop connects to the 8 ohm speaker jack and the 10R resistor is on along with a toggle switch to ground, and speaker sim module is feed off the feedback loop on the 8 ohm jack. I might try and desolder the speaker sim module and see if that fixes the issue.