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MESA/Boogie Mark II-C
MAITENANCE & REPAIR
INTRODUCTION
Malfunctions can usually be cured quickly and easily and, in most cases, a trip to the repair shop
is not necessary. Your Boogie was designed to be reliable, as well as versatile, and simple to
service. By using the outline below, you can easily and quickly run a check and most often remedy
a problem in a few minutes.
CHECKOUT
1. Always view the amp from the rear for 'left' and 'right'; 'front' is toward the knobs and the input
jack.
2. A good basic setting for playing or testing is: Volume 1: 5, Treble: 8, Bass: 0, Middle: 5, Master
1: 3, Lead Drive: 10, Lead Master: 3; EQ OUT; all knobs pushed in, red light on footswitch lit
(indicates Rhythm mode. Lead Drive pull-out performs same function as L/R footswitch.) On back
panel, Presence: 7, Reverb: 4, all-world (Export) power switch set to the correct voltage for the
country you are in (United States, set for 117 volts.)
3. Make certain the speaker works properly and is plugged in correctly: single 8-ohm speaker
goes in 8-ohm jack of 60 watt models BUT in 4 ohm jack with 100/60 switch in 60 RMS position on
Hundred watt models (four 6L6’s) for most powerful operation within speaker ratings. If less power
is desired use 8-ohm jack and 60 RMS.
JUNCTION:
Preamp to Pwr
B:REVERB DRIVER
A:½ LEAD DRIVE AMP
B:½ LEAD DRIVE AMP
A:REV RETURN AMP
DUAL FOOTSWITCH
B:MIXER AMPLIFIER
A:EFFECTS RETURN
B:TONE CONTROL
A:INPUT AMPLIFIER
PHASE INVERTER/
OUTPUT DRIVER
100 WATTS
V4 V3 V2 V1 V5
FRONT ROW BACK ROW
MESA ENGINEERING INC.
MESA/BOOGIE LTD. 1317 ROSS STREET / PETALUMA, CALIFORNIA 94952 / TELEPHONE (707) 778-6565
DIAGNOSIS & REMEDY: AMP IS DEAD, WEAK, NOISY, OR HAS BAD TONE
1. Effects Loop switching jack. If at this point the amp is dead or extremely weak, quickly test the
Effects Loop and its switching jack by completing the Loop with a guitar cord. Occasionally the
internal switching jack of the Effects Return fails to make contact when nothing is plugged in and
hence the signal stops here. If completing the Loop via a simple cable restores performance, then
the jack should be repaired (by judiciously bending the contacts) or better yet, replaced. Jack is
Switchcraft 1.12 (and a 12A will work, too).
2. Pre-Amp Tubes. The most likely cause of an electronic malfunction -- including failure to
operate, bad tone, or any kind of noisy or sporadic operation -- is the failure of a pre-amp tube.
For this reason a spare 12AX7 is attached by a nylon clamp inside your amp cabinet. Begin by
substituting the spare tube in each socket, one at a time, and returning the original tube to its
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