VARI
FIXED
RIGHT
LINE IN
RFI SHUNT
ON
1
2
MC-1 IN
MC-2 IN
OFF
MM IN
SERIAL #
CHASSIS
GROUND
CIRCUIT
MC-1 IN
MC-2 IN
MM IN
LEFT
LINE IN
RFI SHUNT
OFF
1
ON
2
VARI
FIXED
Let the preamp tube(s) cool down, if necessary, before handling. Tube heater
fi
laments are
somewhat more suceptable to damage when warm or hot.
Each tube should require only moderate force for removal and replacement. Gently rock
the tube back and forth a bit during removal or replacement. Avoid bending the circuit board. No-
tice that the heaters of the 6922s are connected in series, and neither channel will function if one
of the
fi
laments is open or burned out, or unless both of the 6922s are installed. Akin to those old
Xmas tree lights in the attic, no? Be careful to straighten any bent tube pins prior to installation;
pin misalignment will make
fi
tting the replacement tube dif
fi
cult or impossible, and may damage
the socket. Be careful to put replacement tubes in the proper sockets.
Never substitute other type numbers of 9-pin tubes without careful research. There are literally
thousands of types that share the 9-pin mechanical basing arrangement, but NOT the internal
electrical connections! Mechanically compatible tube plugs and sockets by no means indicate
electrical compatibility! And random experimenting can easily and quickly destroy the substitute
tube and other parts of the preamp!
Three tube types that are electrically and plug-socket compatible with the 6922 dual triode
are the 7308, 6DJ8 and the ECC88 / E88CC.
Please direct any questions to your dealer or MANLEY LABS for further assistance.
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