Lambda Electronics 71 Instruction Manual - page 18
d) Presence of positive 1) Filament burnout of l2AX7,
low level "HV" voltage as V11. This is easily checked
compared with that by replacement with a new
indicated on the "HV" dial, tube.
poor regulation and high
ripple. (no external load 2) Check voltage across
applied to "HV" output.) capacitor, C2A for voltage
conditions specified on
schematic diagram. If far
below indicated voltage, check
filter capacitor for open
circuit.
3) An abnormal increase of
reference supply voltage
results in reduced power
supply "HV" output voltage.
High bias supply voltage with
associated high reference
supply ripple voltage. This may
be the result of internal grid
to cathode or screen grid short of
6W6-GT, V1. Replace with a new
6W6-GT tube.
4) Burnout of V8, 12AX7 will
cause the bias voltage to rise.
It will have a similar effect
on the "HV" supply of greater
magnitude in the "HV" supply.
Therefore the net result of
filament burnout of this tube
is a rise of "HV" voltage.
e) Apparent satisfactory 6W6-GT tubes, V2 through V6,
operation at 200 MA load exhibit poor cut-off
with rise of ripple voltage characteristic. To check
at zero external load. cut—off characteristic,
operate at zero load and low
"HV" output voltage. Monitor
the "HV" output with a VTVM
or high impedance AC voltmeter.
Remove one tube at a time
until faulty tube is identified.
Faulty tube is identified by
return to normal of "HV"
output ripple voltage. Care
should be exercised in
handling 6W6-GT tubes to
prevent burning of hands due
to touching hot glass envelope.
In removing 6W6-GT tube,
depress retaining clamp
maintaining this position of
the clamp while tube is
removed.
16.