my JP is dead silent

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Frank Pearl said:
what's happening to my JP2c?
I was playing and then it becomes dead silent
i recorded a video: when i play the e-string i hear a weird sound coming from the amp

Suggestions?

https://www.youtube.com/watch?v=38M7iIwXndo

Two stupid questions:

1. Did the speaker cable come unplugged?
2. Did the cab clone speaker switch accidentally get set to "speaker off"?
 
The speaker cable is perfectly connected and cabclone is on "speaker on"
Could it be some preamp tube?
 
Yep it was on all channels.
but i've some update: now it's working again, but this only before i turned up and down the crunch master.
After i turned all the way up i heard the sound again.
i've done the same things on the third channel and i heard the sound.
on the clean channel i heard nothing for a a while but after few seconds, here's the sound again.
For this reason the power tubes must be ok or not?
 
Swap out your speaker cable and see what happens - make sure you get a good quality one. I had a similar issue where everything would come on briefly then go dead quiet. I ended up changing all cables at rehearsal except the speaker cab because I didn't have one handy. Almost was going to do a tube roll, then decided to test it on a 1X12 with a different speaker cable - it worked. Brought the same cable to the next rehearsal to try on a 2X12 cab I leave there and lo and behold it did the trick.

Other thing you can try is 60 Watt mode - if that doesn't work, swap out the inner for outer pair of power amp tubes and keep it in 60 watt mode. That will at least test your power tubes before rolling in a preamp tube.

Finally - I had V1 go on me my first few weeks having the amp. Roll one in there, and if that doesn't work, the Phase inverter/driver (V5) is a good one to swap if its on all channels. It's easier to swap tubes by taking of the front cover - something that was a pain with the MarkV.

The other option is to kill reverb and the FX loop to test if it may be something there.

Good luck - I've found my JP-2C to be a little temperamental compared to my Mark V - but both times I had issues it was an easy fix.
 
That does not sound very good, slim chance it is a preamp tube. What do the power tubes look like when you turn off the standby? Something is pulling the supply down, probably a power tube. Amp should not sound like a compressed piston toy trying to climb a hill.

I would swap inner and outer tubes and run at 60W to see if the same thing occurs. I would probably pull one power tube and power up and attempt to determine if it is a power tube. Manual should have some suggestions to determine if it is tube related. You may need a Mesa service on this one as it may be something else not tube related.

I would also use caution with this amp, output jacks are very close to the FX loop jacks and such that it would be easy to plug into the wrong jack. I need to double check before powering up amp if I ever unplug the speaker. Still I double check every time before I power up on all of my amps.
 
I had something similar happen to mine - ended up being the power connection going in and up in the back of the amp wasn't seated properly.
 
Hey guys. Solved: it was that damned V1.
The amp is playing without issues since 4 days. Hope it is fixed
Thank you for advices!
 
I cannot say I never had any issues with my JP-2C, had one of the 12ax7 on the edge of going microphonic. Replaced all of the preamp tubes and the amp sounds much better. Still have to admit the recording made me think it was something else than a preamp tube. I am glad you found the issue with just a tube swap.
 
When I first got mine it was dead quiet. Now there's a good amount of hiss. I'm pretty sure it's in a tube somewhere but I haven't gone chasing it yet.
 
That actually looked normal. The sudden flash of the blue hue common with power tubes as they are always drawing current. If you see a bright orange flash when you turn on the power that would not be good. Known as heater flash. Bad sign in a power tube but it is okay if a preamp tube does it.
 

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