Fluke 8506A Instruction Manual page 152

GUARDED
SUPPLY
SYMPTOM
VA1
BAD
(+15V) Noisy
VA2
-
BAD
(-15V)
Noisy
VA3
-
BAD
(+30V) Noisy
VA4
-
BAD
(-30V)
Noisy
Vcc (Guarded)
POSSIBLE FAILURE
U3,BR2,
or
Transformer
C3
U4.BR2,
or
Transformer
C4
U1.CR3.BR1, Transformer
Cl
U2,CR4,BR1, Transformer
C2
U5,R5,R3,C5,CR1
<
CR2, Transformer
VA1 and VA2
are
used
as a reference
for
VA3
and VA4.
VA3
and
VA4
could load
down VA1
and
VA2.
Check
by
lifting
the reference diodes
CR3
and CR4.
UNGUARDED
SUPPLY
Vdd (+12V)
U6,C6,C9,C12.BR3, Transformer
Vgg
(-12V)
U7,C13,C10,C7,BR3, Transformer
Vcc (+5V)
U8,R6,R4,C8,C14,C1
1.BR4,
Transformer
The drawing below
identifies test points
on the
Power
Supply
pcb. Input voltages
to the
regulators
should be approximately
5
V
higher than the normal
output
voltages.
If
the output
is
higher or
lower than
specified
and
noise
is
not the problem, the regulator
is
bad.