Mesa Boogie Express

In this video, I repair a mesa boogie express 5:25 amplifier. The infamous C36 tantalum capacitor in the regulated heater supply released the magic smoke and shorted out. I replaced the 7812 regulator IC, C50, C36, and then tested the amp with the proper wall voltage using a step-up transformer.

[@raywarth972]

Wonderful stuff! So informative! I just learned so much about the innards of guitar amps in 7 min 💪 Thanks for the content Eddie!

[@mca1960]

A nightmare to repair.

[@davidpoe177]

Unrelated question on this amp -- Is there a place to find descriptions/meanings of the relay designations in the schematic: RYTS; RYOD; RY2; RYE, RYA, etc?
I am looking at the preamp schematic and having a hard time understanding how the signal flows in any given mode. Is this correct for clean channel in clean mode:
Input --> V2B --> CH1 Tone Stack --> Ch 1 "Gain Control" (1 MA pot) --> V1B?
And then "crunch" mode of channel 1/clean channel would be:
Input --> V2A --> CH 1 Gain Control --> V2B --> CH 1 Tone Stack --> V1B?

[@metalhead3ecr]

I don't have the schematic handy right now, but Mesa has a pretty bad reputation for their schematics. Sometimes going right to left for signal and poor descriptions etc. You might be correct but I recommend injecting a known signal (sine wave at 400Hz for example) and then probing through the amp at every stage to make sure things are correct. I did a similar walkthrough with my own amp in this video. ruclips.net/video/1PB1vcr_Zik/видео.htmlfeature=shared

[@garystickel72]

How did you remove C50?

[@metalhead3ecr]

C50 can be removed by carefully twisting the component CW and CCW until the leads disconnect from
the cap but not the pcb. Much like how you can remove an SMD cap. To get it flush on the board, you'll need to lift that side of the main pcb to solder the bottom

[@garystickel72]

Excellent technique. Thanks for the quick response!