My periodic Mesa rant

[Randall]

Customer asks if I will take a look at his Mesa Nomad 45 212 combo. Hesitantly, I tell him I will take a look, but I mostly don't like taking them on as they are insanely hard to service. He brings it in with a hum across all three channels, and I'm thinking either filter caps or tubes, and it turns out it isn't the tubes. Typical Mesa arrangement where you'd have to disconnect 100 pots, jacks and other wires to get under the board, and then hope the components won't be stubborn or worse to get out, AND hope you don't foul some other connections due to all the flexing of the many wires that have not moved since forever. AND hope what you replaced fixes the problem so you don't start back at square one after it's all put back together. And it's one of the ones with the hidden component designations, you know, printed under them so they can't be read.

No thank you. At this point in my life I don't need to accept every problem that comes my way. I referred him to the two closest Mesa shops, both about 100 miles away, and didn't charge him anything. I feel bad for the guy, but it's not really my problem. I can't fix everything that comes my way, and I am OK with that.

And I hate Mesas.

[xtian]

[DrGonz78]

I could envision a Monty Python skit. "Sure I can take a look at your Mesa". They then set the Mesa on the bench. "Oh it looks real nice", says the amp tech.

[Enzo]

I don't disconnect any wires, I pull off the knobs and remove the nuts and let the pots dangle

[Mick Bailey]

Pull off knob. Nuts. Dangle.

Hey, Beavis - he said nuts.

[Randall]

"I don't disconnect any wires, I pull off the knobs and remove the nuts and let the pots dangle "

I'll send my Mesas to you then.

[Mick Bailey]

Mesa amps are probably my least favourite. It can take up a lot of time to do a simple job. I've had four lately and none have been quick fixes. A Tremoverb with stacked vactrols - some not working, some half way and some intermittent - that has my award for the worst amp ever built. A Nomad with crackle and hum, channel volume discrepancy and volume dropping. A Blue Angel (the one with the potted preamp 'mojo module' section) with a whole pile of problems. Dual Rectifier with an intermittent volume drop on one channel that only happens once every few months.

[Pedro Vecino]

Yesterday I started with an F-50. Perfect sound (no visible degradation) but with a fifth volume in both channels. Very disconcerting
After the classic tests I opted to measure the volume potentiometers and found 8,000 Ohms instead of 125K (two of 250K in parallel). Finally, the problem came from a breakdown in the temporary mute circuit (during switching). A J175 and a bad 2N6426.
I had never seen this problem before manifested in this way.

As for the board removal, I prefer to desolder the potentiometer wires and mark them with points 1, 2 and 3. It facilitates handling and avoids possible mechanical problems. It´s easier for me to desolder and solder three wires than to disassemble and reassemble each potentiometer and its button. I also have a hard time finding the correct Allen key in my box of infinite Allen keys

[minim]

I purchased a Mesa once, prior to learning about amp construction methods. It was an Express 5:50, and it was actually a nice sounding amp. Unfortunately on my very first jam it started smoking and went silent. After obtaining a warranty replacement I couldn't shake the notion that every time I plugged in I was playing a ticking time bomb, and eventually sold it.

Some Mesas in the hands of good guitarists sound awesome. However I'll never buy another, or any other amp with spaghetti internals that look like a parts drawer exploded in there.

[nevetslab]

Mesa Stereo Simul-Class 2:Ninety

I too am not a big fan of Mesa amplifiers as far as servicing goes. They are one that makes me groan when one arrives at my shop door. I will go as far as getting them up on the bench, assuming I can lift them. But, if the problem is found to be deep beyond accessibility, it goes to Mesa Hollywood with a 'beneath-the-breath' utterance of 'good riddance'!

I did purchase this 2U high Mesa Stereo Simul-Class 2-Ninety Power Amp years ago when CenterStaging had a garage sale, and the price was just way too good to pass up: $75 with the employee discount.



The amp does work, but, not unlike many of the Mesa amps, this one 'motor-boats', and I haven't yet cured it of that ailment. This one too, looking at the PCB and build factor that no doubt will require addressing to solve that problem.......I've left it for 'later-man' to tackle some day, when nothing else is pressing.

[Leo_Gnardo]

this one 'motor-boats', and I haven't yet cured it of that ailment........I've left it for 'later-man' to tackle some day, when nothing else is pressing.

Usually that's a weak or kaput filter cap, shouldn't be too tough to troubleshoot. Then you can tackle their goofy cooling fan system, keeps tubes cool on the side by the fan whilst the further away ones are left to roast. Later man, I like that, must be related to my "someday tech." Later, man!

[drewl]

Expensive amp means expensive repair!

Bring 'em on!

I usually don't have too much trouble with them.

The stacked LDR's are a pain.

Most are just noisy as hell with all that gain.

[The Dude]

Yep. If you can afford Mesa price, you can afford Mesa repair price. I fix 'em. An hour is an hour. And, lucky for the customer, I don't charge by the cuss word!

[Danglin' Fury]

Last Mesa I repaired was a 3 channel dual rectifier... I told him I was gonna charge him extra for the pain in the ass, hoping he would just take it to a Mesa service center... he paid extra... damn that money... staring me in the face like that! Luckily I spotted the burnt resistor right off... but yeah... they suck bad...

[drewl]

had to open my big mouth!

Got a Mark IV, thought I was slick finding a shorted V2b orange coupling cap, but I was getting nothing from Channel 2.

Ugh oh, switching problem? Tons of Vactrols! Yikes!

Well, it was only V1b shorted orange coupling cap! Bad idea to use 400v ones.

Now I'm getting bias voltage slowly dropping to one pair of output tubes. Not the 220K feed, or the PI coupling caps.....THE BOARD is causing the problem!

Lifted the cap and feed resistor and wire to tube board and bias is solid as a rock! Now the other side is doing it too!