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Unplug the TUBE53’s AC power cord from the outlet in
use when replacing vacuum tubes.
Do not attempt to replace vacuum tubes immediately after
turning the unit off, as residual heat within the tubes may
cause burning. Wait for the tubes to cool down before at-
tempting replacement.
The vacuum tubes should be considered expendables. The tubes used in the TUBE53
are designed to last fi ve years or longer under normal operating conditions. Should
a fi lament be broken, or should you experience a malfunction (such as noise), you
can replace the vacuum tube(s) following the procedure described below. Contact an
authorized service center if you have any questions concerning the replacement of
vacuum tubes.