2-channel Dual Rec Troubleshoot - Loud 'Pop' On Powerup/Down

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slysendice

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Hey all,

As the title suggests, I would really appreciate some help troubleshooting a new issue I've been having with my dual rectifier as of today.

Earlier, when I was playing guitar, I noticed the volume suddenly dropped slightly, and my tone became a bit more "woofy" on the low end - as if I had lost some definition. I figured my ears were just deceiving me, so I continued to play. When I had finished playing, I turned the amp off as usual, and I heard a huge "POP" sound. Naturally, this concerned me, so I began troubleshooting steps (switching out cables/guitars, checking tubes, etc.). I cannot seem to figure out where this sound is coming from. The only thing that I can think of that I haven't checked is the fuse.

Here is a video I took of exactly what my issue is:

https://www.youtube.com/watch?v=3dFDjPXgS8s (sorry I don't know how to embed videos, if at all possible).

If anyone has experienced/resolved a similar issue, or knows what the issue may be, I would very much appreciate some help. I am hoping it'll be a relatively easy fix as I just bought this in January and I'm hoping the dude I bought it from wasn't just trying to offload this amp knowing it was on the fritz.

Anyway, thank you for your time!
 
Actually, I can't necessarily verify that it's not one of the preamp tubes. So I suppose that's a possibility as well, considering the pop seems to occur whenever the preamp is engaged (taking out of standby) and disengaged (powering off the amp).
 
Try changing tubes. That pop is energy building up and shooting to ground. If it is continually happening, then something is not connected correctly and keeps collecting energy. I think preamp tubes are a good guess, but power tubes wear faster.

If you have a set of tubes from another amp which you know are good, swap them over or try one tube at a time. V3 and V4 are most common when there is an early failure. If there's no change, try the power tubes. If none of that works, contact Mesa.

Make sure the tubes are seated correctly, too, and that the contacts are clean.
 
I think I have a spare preamp tube somewhere, I will try swapping them one by one tonight. I'm fairly certain it's not the power tubes - while I don't have any spares, I tried running half power and every combination of tubes I tried still had the same problem. Here's hoping a new preamp tube will solve this.

Thank you for your help!
 
Don't overlook your rectifier tubes! They are directly in the power section of the amp, even when switched to Solid State (diode) rectifier.

With the amp set to solid state (diodes) it is safe to remove the rectifier tubes (with the amp off of course) and power cycle the amp.

HTH

Dom
 
Huh, I hadn't considered this. It's certainly a possibility as I have no idea how old any of these tubes are.

So essentially, if I have the amp switched to Diode rectification (which is the setting I use it on anyway), I can remove both rectifier tubes, power it on/off and see if this persists? I'll give that a shot this evening, too.
 
Well folks, it appears that it is not anything tube-related. I decided to just take all the tubes out and replace them with the ones in my Electra Dyne (which is working flawlessly). I also tried taking out the rectifier tubes and running it in diode rectifier mode. The issue persists. So looks like I will be taking the ol' Rectifier to my local guitar shop to see if they can figure out what's going on.

I likely won't be able to get it there until Thursday. So in the meantime, if anyone has any info they'd like to add (that can be executed with severely limited tools and knowledge) I would much appreciate any help.

Thank you to all who have contributed!
 
Probably filter caps (or other caps) starting to go. They are only rated for 10-15 years of daily use, less if the amp sits unpowered.
 
vick1000 said:
Probably filter caps (or other caps) starting to go. They are only rated for 10-15 years of daily use, less if the amp sits unpowered.
That's what the tech suggested. Took it in last week, fingers crossed I'll have it back soon.

Thanks everybody for your suggestions!
 

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