Panasonic NN-8508 - Page 21

NN-8508, NN-8558
NN-8808, NN-8858
NN-8808P
COMPONENT TEST PROCEDURE
CAUTION FILAMENT
WINDING
TERMINALS
1.
High
voltage
is
present
at
the
high
voltage
terminal
of
the
high
voltage
transformer
during
any
cook
cycle.
2.
It
is
neither
necessary
nor
advisable
to
attempt
measurement
of
the
high
voltage.
..
3.
Before
touching
any
oven
components,
or
wiring,
always
unplug
the
oven
from
its
power
source
and
discharge
the
capacitor.
(See
page
15.)
SECONDARY
WINDING
TERMINALS
TERMINALS
1. High voltage transformer (See Fig. 34)
(A)
Remove
connections
from
the
transformer
terminals
and
check
con-
OVEN
CHASSIS
tinuity.
(B)
Normal
(cold)
resistance
readings
should
be
as
follows:
Fig.
34
Secondary
winding
paeeevecccrevccetessenseeerensesess
Approx.
802
~110Q
Filament
winding
Approx.
0Q
Primary
winding
Soe
eigia
Sieg
ace'eid
aie
Suisiarain
Seieheiwrain’s
sielereve
ma
sya.
Approx.
oQ~
129
ANTENNA
2. High voltage capacitor
(A)
Check
continuity
of
capacitor
with
meter
on
highest
OHM
scale.
(B)
A
normal
capacitor
will
show
continuity
for
a
short
time,
and
then
indi-
COOLING
cate
9MQ
once
the
capacitor
is
charged.
FIN
(C)
A
shorted
capacitor
will
show
continuous
continuity.
(D) An open capacitor will show constant 9MQ.
(E)
Resistance
between
each
terminal
and
chassis
should
be
infinite.
3. Diode
(A)
Isolate
the
diode
from
the
circuit
by
disconnecting
the
leads.
SS
FILAMENT
(B)
With
the
ohmmeter
set
on
the
highest
resistance
scale,
measure
the
MAGNE
TRON
~
TERMINALS
CASE
resistance
across
the
diode
terminals.
Reverse
the
meter
leads
and
again
observe
the
resistance
reading.
Meter
with
6V,
9V
or
higher
voltage
batteries
should
be
used
to
check
the
front-to-back
resist-
ance
of
the
diode,
otherwise
an
infinite
resistance
may
be
read
in
Fig.
35
both directions.
A
normal
diode’s
resistance
will
be
infinite
in
one
direction
and
sever-
PNM
al
hundred
kQ
in
the
other
direction.
KEY
PAD
;
NN-
a
NN-8508
NN-8808(P})
NN-8508
4.
Magnetron
(See
Fig.
35)
aches
ae
aoe
ce
Continuity
checks
can
only
indicate
an
open
filament
or
a
shorted
magnetron.
To
diagnose
for
an
open
filament
or
shorted
magnetron,
ee
Sale
ee
(A)
Isolate
magnetron
from
the
circuit
by
disconnecting
the
leads.
(B)
A
continuity
check
across
magnetron
filament
terminals
should
indi-
sie
por
[ef
ewe
fe
[oe
(C)
A
continuity
check
between
each
filament
terminal
and
magnetron
Gita
5.
Membrane
key
board
(Membrane
switch
assembly)
Check
continuity
between
switch
terminals,
by
pressing
an
appropri-
STAND/TIMER
Edis
10
MIN
ate
pad
on
the
key
board.
The
contacts
assignment
of
the
respective
pads
on
the
key
board
is
AS.REHEAT
as
shown
in
Fig.
36.
ASTARTICLOGK
ROOM
TEMP
AS.REHEAT
BAI
ep fe
AS.REHEAT
BRi
| | = fae
SEI
DONENESS
LESS/MORE
A.REHEAT 1
Fig. 36