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Mesa Boogie amps have more bells and whistles than a Shriner Circus parade and this is one of their most complex designs - the Dual Rectifier Roadster. This amp came to me with a supposed bad output transformer, but after repairing that I found other problems, namely NO output or very, very LOW output. In this video, we'll diagnose the problem through the dense morass of schematic and PCB and find out why so many technicians loathe working on Mesa amps.
SPOILER ALERT: The fault ends up being with the switching matrix. The amp had entered a state known to Mesa engineers as "permanent mute" or "permamute". To fix this issue requires replacing one or more of the JFET transistors in the switching matrix. Not something you want to do with a bad soldering iron tip! This video includes an overview and discussion of this ingenious mute switching circuit for which Mesa holds a patent.
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