7
Installation of Tubes, Tube Cover, Location and Ventilation
Small Signal Tubes:
1. Locate a 12AX7A Tube.
2. On the top left side of the amplifier, locate the Tube
Socket that has the nomenclature V1 12AX7A next to it
on the chassis. Refer to figure 4 and 5.
3. Orient the Tube so the area where no pins are located on
the base of the Tube is aligned with the corresponding
area on the Tube Socket.
4. Carefully insert the Tube into the socket until the base
of the Tube is fully seated in the Tube Socket.
5. Repeat the above steps for the remaining two 12AX7A
Tubes at locations V2 and V5.
6. Locate a 12AT7 Tube.
7. On the top center of the amplifier, locate the Tube
Socket that has the nomenclature V3 12AT7A next to it
on the chassis.
8. Insert the Tube, following the same procedure as in
steps 3 and 4.
9. Repeat steps 6-9 for the remaining three 12AT7 Tubes
at locations V4, V6 and V7.
Caution: To prevent electrical shock make sure the
MC275 Tube Cover is installed before con-
necting the AC Power Cord.
Before operating the MC275, locate the previously re-
moved Tube Cover and perform the following steps:
Installing the Tube Cover:
1. The Tube Cover has a wide opening along one side of
its longer dimension. Orient this wide opening so it is
facing towards the three large transformers.
2. Carefully place the Tube Cover onto the MC275 while
at the same time aligning the two chassis mounted ball
studs with the Tinnerman Clips in the cover. Refer to
figure 6.
The MC275 can be placed upright on a table or shelf,
standing on its four feet. It also can be installed in a piece
of furniture of your choice. Do not install the MC275
directly above a heat generating component. Adequate
ventilation extends the trouble free life of the MC275. The
suggested minimum space for operating the MC275 is 22
inches (55.88cm) in width, 18 inches (45.72cm) depth, and
21 inches (53.34cm) in height. Always allow air to flow
through the ventilation holes on the bottom of the amplifier
and a means for the warm air to escape at the top. If the
MC275 is installed in a cabinet, a quiet running ventilation
fan can be a definite asset in maintaining the coolest pos-
sible operating temperature. Refer to figure 7.
Location and Ventilation
Warm Air
Cool Air
Figure 7
Figure 6
Ball Stud Fasteners
KT88/6550
Tubes
Figure 5
12AX7A
Tubes
12AX7A
Tube
12AT7
Tubes
12AT7
Tubes
