6
Installation
Vacuum Tubes
Before operate your AP990C
Your AP990C amplifier is shipped with the vacuum tubes packed in foam
blocks. These must be unpacked and installed before you attempt to operate
the amplifier. Included are two matched pair of KT-88 or KT-150 output tubes,
and two 12AX7, two 6SN7 dual triodes used in the input stage. Proceed
according to the following instructions.
Carefully remove each vacuum tube from its protective foam and match its lo-
cation “V” number (written on the base of the tube) to the “V’ number printed
next to each socket. Firmly seat each tube in its matching socket, taking care to
“key” the tube pins to the socket holes. Retain the foam blocks with other
packing materials for possible future use.
If you are using the optional tube cover, be sure the AP990C is first turned off.
Remove the top cover screws, and install the cover on top of the top plate. Insert
and retighten screws.