Anyone want to try and diagnose this fault?

[screamingdaisy]

If you listen to the audio clip you can hear a harsh clipping while playing. The clip was recorded on channel 1, plugged straight into the amp with the loop bypassed.

https://dl.dropboxusercontent.com/u/37532735/Forum%20Stuff/Amp%20Clipping.mp3

Backstory...

I first noticed that harsh clip on the clean channel years ago (I've owned it for 5 years) but it was always super faint and only happened on the bridge pickup. Even though I knew it was there I've never dealt with it because I never play clean on the bridge pickup so it was a bit of a non-issue for me.

A few days ago I was playing when the guitar cut out and I got hiss/white noise through the speakers. I thought one of the power tubes had failed/shorted so I quickly looked in the back and none of the power tubes had red plated. I flicked it into standby for a second or two then turned it back on while watching the tubes. Zero issues and it passed audio fine.

Since then the faint clipping has become not-so-faint and is infecting all three channels. I've since swapped all the preamp tubes, the guitar cable, speaker cable and power cable. I installed brand new power tubes, rectifier tube and fuse. I've unplugged everything I can, including the footswitch and reverb. The loop is bypassed. I've tried every power setting (10w, 45w, 90w, variac on/off, tube rectifier on/off, triode/pentode) and it doesn't affect the clipping sound.

Anyway, I'm at the point where I've swapped every user serviceable component that I can and the obvious answer is to call Mesa and book a repair... but they're closed until Monday and I have time to be curious.

Amp settings below... nothing extreme.

 

[barryswanson]

Does your fan still work?

 

[screamingdaisy]

Yes. Why?

Edit: Makes the clipping sound both with the fan on and off...

 

[JCDenton6]

Maybe a pot or cap is going bad, or a solder joint that loosened over time in the preamp (component or wire)?

Could also be a screen grid resistor on the way out.

 

[APEMAN]

-

 

[screamingdaisy]

... My guess would be a broken component in the V1 area. First I would start to check voltages and stabilisation for V1...
Good luck!

That's going beyond my capability. I've done simple repairs in the past and if this was a simple old school amp I'd be inclined to poke around for the learning experience... this however I'm not going to touch. :lol:

 

[screamingdaisy]

Booked it in for repair.

You know, the nice thing about this whole experience is that I get to spend some quality time with my Recto. For the last little while every time I plugged into it I would play it for a song or two and say, "It's nice, but it's no Mark V."

But now that I don't have a choice I'm actually playing it long enough to remember why I liked them so much.

 

[knotts]

You know, the nice thing about this whole experience is that I get to spend some quality time with my Recto. For the last little while every time I plugged into it I would play it for a song or two and say, "It's nice, but it's no Mark V."

But now that I don't have a choice I'm actually playing it long enough to remember why I liked them so much.

What are the chances that when the V comes back it takes a back seat to the Recto?

 

[screamingdaisy]

What are the chances that when the V comes back it takes a back seat to the Recto?

No idea. I've been playing Rectos for 12 years and Marks for 7. Up until a year or two ago I would've called myself a Recto guy, then one day the Mark just kind of took the lead and that was that.

Once I stopped dialling in "Metallica" by default into the Mark V and figured out how to dial up more hard rock based tones the amp started to fit my needs better and started getting more play time, and conversely the Recto started fitting my needs less and getting less play time.

Now I'm actually taking the time to search out new settings in the Recto... the shift away from "Metallica" and more towards a Soundgarden/Alice in Chains kind of vibe is now happening on the Recto and I'm really digging what I'm hearing.