11
PF-20T / PF-50T Bass Guitar Amplifier
TUBE BIAS DIAGNOSIS
Condition Problem Solution
Green comes on, then red No problem The longer the green LED
is lit prior to the red LED
illuminating, the better
matched the set of tubes
Red comes on, then green Tubes not properly
matched
Set slightly prior to when
the green LED illuminates.
Obtain a matched tube set
when possible
Red comes on, no green One or more tubes are non-
functional
Check to make sure tubes
are all seated properly; if
so, nd and replace bad
tube(s)
None on Possibly no high voltage,
bad Bias control, or bad
tube(s)
Have unit checked by a
service technician
Both on all the time Possible bad Bias control
or bad tube(s)
Have unit checked by a
service technician
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