Mesa Baron

I like to run my Baron in 2/3 pentode, 1/3 triode mode. Yes, the triode mode is sweeter sounding, but i need a bit more power to drive the Maggies. In full triode more, bass can be a bit soft ...

The original caps in the Barons were leakers I read it on a forum so I contacted mesa about it and it was actually true.When I flipped amp and took off bottom plate low and behold they were leaking and had them replaced.Great amp though but have since sold

Agreed, there was one cap in each channel that leaked; Mesa got a bad batch of that particular cap, they were pretty unhappy about that.   Mine were replaced early on (22 or 23 years ago)  Except for blowing bias resistors every few years, while using El34 tubes, (the 4 bias resistors are user replaceable if you have a little skill with a soldering iron) it has been completely reliable.   The bias resistors as a point of failure was an intentional design choice, sort of a backup to the fuses, of which there are 3 per channel.   As an aside, “upgraded” fuses were a downgrade. 
   I eventually got tired of replacing the bias resistors, and at the urging of Mesa, went back to 6L6 and 5881 tubes, the way the Baron was originally designed, and that problem went away.  I preferred the midrange sound of el34s, but the 6l6s sound fine, and have a little better bottom end.  Everything’s a trade off.
    It’s still going strong, after 24 years.  Occasionally some noise, about time to see if Mesa will replace the ps caps.  The same tech at Mesa is still there, and he has dissuaded me from that a couple of times, “if it ain’t broke...”  Their customer service is nonpareil.
  My only complaint is about running a space heater in summer, but that’s the price for running an amp with 12 power tubes,
    

Glad to see this beloved amp is still out there and kicking so well for many folks. 

Ive had mine since 1998 and loved every second of ownership. 

Until about three weeks ago it still ran like a champ. Tri-tube mod etc from the outset. For the last couple years I’d been running KT77’s in it to glorious sonic results!  Three weeks ago one tube failed in my right channel taking an SR Orange fuse with it and two bias resistors. I contacted my CS contact at MESA and Michael, the tech. Took some pics of internals and Michael said my 47uF caps were shot undoubtedly causing the tube to short. 

MESA sent me the resistors, caps etc. but I decided to replace them with Mundorf MLYTIC along with the 30uF caps. A bit larger so some alternate fitting needed to be done. Also replaced all other above board electrolytics with KAISEI caps. Lastly I nailed one of the tube strapping wires connecting all of the tubes on each side with my iron melting the insulation. So, I replaced with Duelund Wire 1 solid silver 18ga flat annealed wire sheathed in silk conditioned in a proprietary oil.

Holy cow is she sweet now!  Using a set of MESA Winged C EL34 tubes for now and it’s sweet.  For years I’d used the EH KT90 tubes and those babies are very robust and solid!  Sound like a larger more solid EL34 with insane drive. I still have them and will try sometime soon. People had a tendency to over bias them running way too hot. Set bias at the 120 watt mark on the meters same as the EL34 and good to go. It’s only 2-3 mA higher bias per tube than setting at the 5881 setting.

Next year my plans are when I can afford it to replace the 8 Wima 0.1uF input coupling caps with Duelund CAST caps but that’s about a grand to do.

For now it’s a sweet amp again and then some.

BTW Michael advises me the 12 4700uF United Chemi Con main power supply caps are not replaceable. Sadly they are snap in but soldered in place on the board underneath requiring pull out of the board. Every time they’ve attempted or did replace those caps years ago due to the Sprague versions leaking they had to replace the entire board to do so. MESA no longer stocks the board so if/when your UCC 4700uF caps go that’s about it. 

Michael did confirm however the UCC caps are VERY robust in construction so they should still last many years. 

Enjoy this killer amp!