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LAB.GRUFFEN
NOV.
92
1
)
2
)
3)
4)
5)
6)
7)
8
)
9)
10
)
Service in
SS
1300 power
supplies.
(
VALID
FOR
UNITS
WITH PSA,
ALT.
PSUA
AND
PSUB
BOARDS.
)
Required
measurement
equippment:
-Audiogenerator
-AC-voltmeter/
THD-meter
-DVM
-Two
channel
oscilloscope
for
audio
-Variac 0-280V,
6A
-50
MHz
oscilloscope,
ex.
Tek
2225
with lOOx probe
ex.
Tek P6009
-Isolationtransformer
for
the mains,
1:1
Turn TP3
fully
counter
clockwise.
Change
FI on
the
PSA
(
PSUA
).
Increase the
main
voltage slowly
by
the
variac.
Measure
the voltage across Cl.
a)
No
voltage:
-change
R1
(
R5
PSUA
).
b)
The
current increase
quickly:
-check
Dl-PSA
-check
Ql, Q2, Q3.
It
is
now
possible to increase
the voltage
across
Cl
to
approx.
300
V
without
currentrush.
Connect an
oscilloscope via
a
isolation
transformer
across
Ql
collector
and
emitter
Turn
TP3
slowly
until
a pulse
is
visible
on
the
scope.
The
frequency
is
approx.
27
kHz.
If
the
graph
is
seen,
go
to
item
10).
If
only
narrow
spikes
is
seen,
check
the following
components.
a)
D13,
D14 -PSA
(D3,
D4 PSUA)
or
the output
circuits.
b)
D1
(
C5
,R1,
R2,
R3
)
-makes
U1
go
into
over voltage
protection.
c)
Ql-PSA
-the softstart circuit will
not
deliver
enough
power.
d)
U1
-the
output
will
remain
low
all
the
time.
If
ringing occur
after
the flyback
pulse,
it
depends on broken
D2
or
R4, R5/C6.
Turn
TP3
fully
clockwise:
a)
Check
the outputvoltage
on
C22,
C23 -PSA
(C13,
C15 PSUA)
for
82.5V
DC
-
Adjust with
TP2.
b)
Check
the
softstart circuit
by
turn
on and
off
the
mainswitch and
look at
the
oscilloscope.
c)
Increase the
power by
applying a audiosignal
to
the
amplifier
and
turn
up
the gaincontrols.-The pulsewidth
will
increase.
d)
Check
the
over-/
undervoltage
protdftion
circuits
by
turning the
variac
up
to
280
VAC
and
down
to
130
VAC.
(No
bad
).
V/'
CIV' IX r
3
OOv
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