Panasonic NN-8508 User manual

ORDER NO. MOD88090
ual
Microwave Oven
NN-8508, NN-8558
NN-8808, NN-8858
NN-8808P
Specifications
Power Source :
120 V AC Single Phase 60 Hz
(50/60 Hz for NN-8808P only)
Power Requirement : 1,400 W (12.2 A)----- Microwave
1,500 W (12.5 A): Bake and Broil
Output : 700 W:-:--:Full Microwave Power
1,400 W::--:- Heater |
Microwave Frequency : 2,450 MHz
Timer : 99 Min. 99 Sec./9 Hr. 99 Min.
Outside Dimensions : 22” (W) X 17-1/4” (D) X 15-3/16” (H)
558 mm (W) X 439 mm (D) X 385 mm (H)
Oven Cavity Dimensions : 14-7/16" (W) X 14-5/8” (D) X 9-1/8" (H)
367 mm (W) X 372 mm (D) X 232 mm (H)
Weight : 55 Ibs (24.5 kg)
Specifications subject to change without notice.
Matsushita Services Company Panasonic Hawaii, Inc. Panasonic Sales Company,
i 50 Meadowland Parkway, 99-859 Iwaiwa Street Division of Matsushita Electric
Secaucus, New Jersey 07094 P.O. Box 774 of Puerto Rico, Inc.
Honolulu, Hawaii 96808-0774 Ave, 65 De Infanteria, KM 9.7
® Victoria Industrial Park
Matsushita Electric Carolina, Puerto Rico 00630
of Canada Limited
5770 Ambler Drive, Mississauga,
: ; Ontario, L4W 2T3
Copyright© 1988 by Matsushita Electric Corporation of America, All rights reserved. :

core phat
NIN-8508, NN-8558
NN-8808, NN-8858
NN-8808P
This
service
manual
covers
products
for
following
markets.
When
troubleshooting
or
replacing
parts,
please
refer
to
the
country
identifications
shown
below
for
your
applicable
‘product
specification.
Me
For
U.S.A.
and
some
of
Latin
America
countries
--For Canada
fe Ap ; WARNING
4.
This
product
should
be
serviced
only
by
trained
qualified
personnel.
2.
Though
this
product
has
been
manufactured
in
compliance
with:
“Federal
Performance
Standard
21
CFR
Subchapter
J”
(D.H.H.S.):
U.S.A.
models
or
“Radiation
Emitting
Devices
Act’
(NHW):
Canadian
models
it
is
very
important
all
repairs
should
be
made
in
accordance
with
procedures
described
in
this
manual
to
avoid
being
exposed
to
excessive
microwave
radiation.
;
3.
Check
for
radiation
leakage
after
every
servicing
according
to
the
“procedure
for
measuring
radiation
leakage”
on
page
24.
4.
Any
serviceman
who
learns
of
any
accident
pertaining
to
microwave
radiation
leakage
should
immediately
notify
the
appropriate address listed below.
IN
U.S.A.
Matsushita
Services
Company
IN
PUERTO
RICO
PSC
(MSC)
50
Meadowland
Park
way,
(PSC)
Ave.
65
De
Infanteria,
KM
9.7
Secaucus, New Jersey 07094 Victoria Industrial Park
Attention: Engineering Support Division. Carolina, Puerto Rico 00630
[phone] [phone]
IN
HAWAII
PHI
IN
CANADA
Matsushita
Electric
of
Canada
Limited
(PHI) 99-859 Iwaiwa Street (MELCA) 5770 Ambler Drive, Mississauga,
P.O. Box 774 Honolulu, Hawaii 96808-0774 Ontario, L4W2T3
[phone] [phone]
5.
There
are
special
components
used
in
the
microwave
oven
which
are
important
for
safety.
These
parts
are
marked
with
a
ZX
on
the
replacement
parts
list.
It is
essential
that
these critical parts should be replaced with
manufacturer's
specified
parts
to
prevent microwave
leakage,
shock, fire,
or
other
hazards. Do
not modify the
original
design.
PRECAUTIONS
TO
BE
OBSERVED
BEFORE
AND
DURING
SERVICING
TO
AVOID
POSSIBLE
EXPOSURE
TO
EXCESSIVE
MICROWAVE
ENERGY
(A)
Do
not
operate
or
allow
the
oven
to
be
operated
compartments,
check
the
magnetron,
waveguide
with
the
door
open.
or
transmission
line,
and
cavity
for
proper
align-
(B)
Make
the
following
safety
checks
on
all
ovens
to
ment,
integrity
and
connections.
ors
be
serviced
before
activating
the
magnetron
or (D)
Any
defective
or
misadjusted
components
in the
in-
other
microwave
source,
and
make
repairs
as
terlock,
monitor,
door
seal,
and
microwave
genera-
necessary:
:
tion
and
transmission
systems
shall
be
repaired,
re-
(1)
Interlock
operation
placed,
or
adjusted
by
procedures
described
in
(2) Proper
door
closing
this
manual
before
the
oven
is
released
to
the
(3)
Seal
and
sealing
surfaces
(arcing,
wear,
and
owner.
other damage)
(E)
A microwave
leakage
check
to
verify
compliance
(4)
Damage to or
loosening
of
hinges
and latches.
with
the
Federal
Performance
Standard
should
be
(5)
Evidence
of
dropping
or
abuse
performed
on
each
oven
prior
to
release
to
the
(C)
Before
turning
on
microwave
power
for
any
service
owner.
test
or
inspection
within
the
microwave
generating
CONTENTS
PRECAUTIONS
TO
BE
OBSERVED
BEFORE
AND
DURING
K
FACTORS
AND
POWER
LEVELS
vv
esstesssresetsreeieeeteisereees
mae
SERVICING
TO
AVOID
POSSIBLE
EXPOSURE
TO
CAUTIONS
TO
BE
OBSERVED
WHEN
TROUBLESHOOTING:-**-"+----
15
EXCESSIVE
MICROWAVE
ENERGY
*i-0s-rsescssstercsrestesreseeeteecenenecs
2
DISASSEMBLY
AND
PARTS
REPLACEMENT
PROCEDURE:***--"-""*
16
FEATURE
CHART
&
LOCATION
OF
NAMEPLATE
*eerrrerrcesrteeseteeeeses
3
COMPONENT
TEST
PROCEDURE
crertrtrctetetreetecteceee
seer
eer
ne
neenees
94
FEATURE
DIAGRAM
&
CONTROL
PANEL
«rrsrstrrrrrrrtttettrrerrrereere
4
MEASUREMENTS
AND
ADJUSTMENTS
sccceccerccesccsceteeesetteeen
esse
ee
23
OPERATION
PROCEDURE
--0-+0+-+--+sessesrseeseeestereerseesetesttstceseerenaees
5
PROCEDURE
FOR
MEASURING
MICROWAVE
ENERGY
LEAKAGE
--
24
ACCESSORIES & COOKING UTENSILS bane e eee nee eer e teen nee neta eeassesenneas 6 TROUBLESHOOTING GUIDE errr errr eter ret teeter reer errr r ere eee eer
SCHEMATIC
DIAGRAM
(FOR
U.S.A.
MODELS)
<0
-r0ser0rcerereeeerees
7
DIGITAL
PROGRAMMER
CIRCUIT-TEST
PROCEDURE
vy
SCHEMATIC DIAGRAM (FOR CANADIAN MODELS) aed t ee ee arn eneeecrneres 8 EXPLODED VIEW AND PARTS LIST seer santes once enter vee sacreesonen ee yes
SCHEMATIC
DIAGRAM
(NN-8808P):*+-020-200
sce
ceretsertereeseetetereeteees
9
DIGITAL
PROGRAMMER
CIRCUIT
PARTS
LIST:--
seen
DESCRIPTION
OF
OPERATING
SEQUENCE
Peeve
eereee
er
rete
rere
ree
ere
eee
10
AUTO SENSOR EXPLANATION,
gee)
~2-

NN-8508, NN-8558
NN-8808, NN-8858
NN-8808P
FEATURE CHART
NN-8858
NN-8558 NN-8808P
CYCLIC DEFROST
THREE STAGE COOKING
AUTO WEIGHT DEFROST
AUTO REHEAT
AUTO WEIGHT COMBINATION COOKING
COMBINATION
—
TIME
COOKING
a
ee
BAKING
—
AUTO
PREHEATING
enn
Mus
BROILING — AUTO PREHEATING
S
[aromur SSSCSC~C“S*S*S*S*~‘“dSCSCSC“‘“ CT
PToericex SSSCSC~C~“‘“iRSC“‘ MSCS
PRODUCT DESTINATION LOCATION OF NAMEPLATE
MODEL
wee | —[o
wes [os
[wae [0 |
%% 2K For U.S. Military Market
Fig. A
The nameplate is located on frame of the escutcheon base as
illustrated in Fig. A.
The model and serial numbers will be found on this nameplate.

NN-8508, NN-8558
NN-8808, NN-8858
NN-8808P
CONTROL PANEL
NN-8808/8858/8808P
@Display Window
@Time Pads
@Power Pad
@Stand/Timer Pad
@Bake Cooking Pad
©AW. Combination Pad
@1.0 lb Pad
®Cooking Guide
@aAuto Reheat Pads
(Auto Sensor Cook Pad
@Stop/Reset Pad
QDA.Start/Clock Pad
@Combination Cooking Pad
(@Broiling Pad
(AW. Defrost Pad
(0.1 Ib Pad
@Doneness Pad
@®Start Pad

NN-8808P
. OPERATION PROCEDURE |
Pecans eras STEP 1 STEP 2 STEP 3 STEP 4 STEP 5
[craven 2 times
[start |
(TWO STAGE)
ar | Se [reece
me ai [ |
mm oe Sf
AUTO REHEAT
AUTO SENSOR
REHEAT
NN-8508, NN-8558
NN-8808, NN-8858
For
more
detailed
operating
sequence,
see
pages
31
through
33.
NOTES WHEN PROGRAMMING:
1. CLOCK SET:
(1) To reset time of day, repeat step 1 through step 3.
(2)
The
clock
will
keep
the
time
of
day
as
long
as
oven
is
plugged
in
and
electricity
is
supplied.
(8) To delete “88:88” indication, touch Stop/Reset pad.
2. AUTO SENSOR REHEAT:
(1) Reheat covered with lid or plastic wrap.
(2) Stand time or a power level can be programmed after Auto Sensor
Reheat.
For best results follow these recommendations:
(1) Select correct category of food being reheated. All foods must be
previously cooked.
(2) Make sure glass tray in the oven is dry to assure best cooking results.
(3) Foods should always be covered loosely with plastic wrapper lid.
(4) Foods weighing less than 4 ounces and more than 32 ounces should
be reheated by power and time only.
(5) All foods should have a covered stand time of 3 to 5 minutes.
(6) The surrounding room temperature should not be above O5°F.
Inaccurate cooking may result.
If desired
AUTO SENSOR A. [eae | [start |
Ree START
AUTO
WEIGHT
AUTO
WEIGHT
COMBINATION [1.o18]o.118] 0.118) START
COMBINATION-
er
en
DO NOT
(1) Open oven door during reheat time. Opening door may cause inaccu-
rate cooking results. The oven door may be opened once the timed
countdown appears in display window. ~
(2) Reheat bread and pastry products. Use manual power and time.
(3) Cook or reheat raw or uncooked food.
(4) Use reheat if oven cavity is warm.
{5) Use reheat for beveragas.

NN-8508, NN-8558
NN-8808, NN-8858
NN-8808P
ACCESSORIES & COOKING UTENSILS
Accessories
and
Use
iii
titi
titi
titi
tite
tigi
titi
eit
it
0
0
00MM
iit
Oven Pan
Oven Pan is used for BAKE and
BROIL. Do not use the Oven Pan
for Microwave or Combination.
COMBINATION
AGES
ARE ra.
Spatter shield
Metal Tray
Spatter Shield
The Spatter Shield is used for
COMBINATION and BROIL to
help prevent spattering.
Metal Tray
Metal Tray is used for
COMBINATION and
MICROWAVE. Remove
Metal Tray when using BROIL or
BAKE.
BAKING
Oven Pan
. Metal Turntable |
The metal turntable should always
remain in the oven. It should never
be removed when oven is in
operation.
BROILING
Ko)
ESE E
Spatter shield Oven Pan
Cooking Utensils iwininisiniaiein yan ninn eae nae AH RE NE
Following is a summary chart which describes the correct use of cooking utensils in your microwave/flat heater oven.
Cookware
Heat-Resistant Glass,
Glass-Ceramic (Pyrex®,
Fire King®, Corning
Ware®, etc.)
(Do not use
utensils with
metal trim)
Bake
YES YES
YES
(Do not use
utensils with
metal trim)
YES*
(Start cooking NO
time only)
Plastic Films & Wraps YES* N
Microwave-Safe Plastics
Paper Products
Straw, Wicker & Wood
Browning Dishes
O NO
Combination
(Do not use
utensils with
metal trim)
(Use metal oven
accessories
included with
this oven only)
NO
NO
NO
Broiling
YES YES,
if heat-safe
to 450°F
YES NO
YES
NO
NO NO
*If Bake or Combination was used prior to Microwave, allow metal tray to cool 15-20 min. before using these dishes.
NOTE: FOR MORE INSTRUCTIONS ON THE CORRECT USE OF UTENSILS IN YOUR OVEN, PLEASE READ
THE INTRODUCTION SECTION IN THE PANASONIC COOKBOOK.

NN-8508, NN-8558
NN-8808, NN-8858
NN-8808P 2
SCHEMATIC
DIAGRAM
(FOR
U.S.A.
MODELS)
-
NN-8508/NN-8808/NN-8858
APH
PLUG NOTE: Door is closed.
cK
ra
OE
ps
Unit
is
not
operated.
LATCH
Ground
THERMAL
SWITCH
A
CUTOUT (PRIMARY) zr Chassis
AC120V
60Hz
LOWER | UPPER ] SHORT
HEATER] HEATER! SWITCH
LATCH! P120
SWITCH B HIGH VOLTAGE
(SECONDARY) TRANSFORMER
LOW VOLTAGE
TRANSFORMER
DIGITAL
PROGRAMMER
CIRCUIT
of0
HUMIDITY
SENSOR
(NN-8808/
8858)
OVEN TEMP SENSOR
(OVEN THERMISTOR)
WIRING
DIAGRAM
NOTE:
#*When
replacing,
check
the
lead
wire
color
as
shown.
*Colors
shown
by
(_
)
indicate
colors
of
lead wire
connector housing.
LATCH SWITCH A HUMIDITY SENSOR POWER RELAY B
TOP (RY2)
COLOR
ORANGE
BLUE
BROWN
WHITE
| OR __|
| BL
| BR
|W
| YT YELLOW
| Rd
| GR
|B
CK
LATCH
SWITCH
B
SHORT
SWITCH
POWER
RELAY
C
POWER
RELAY
D B
Auee
BOTTOM (OUTSIDE) BOTTOM (INSIDE) (RY3) (RY4)
aryw | BROWN
/WHITE
BL
Y
GR Y
/W

NN-8508, NN-8558
NN-8808, NN-8858
NN-8808P
SCHEMATIC DIAGRAM (FOR CANADIAN MODELS)
NN-8558/NN-8808 CPH
PLUG
WHITE BLACK
AC120V
60Hz
THERMAL
CUTOUT
VARISTOR
LOW VOLTAGE
TRANSFORMER
WIRING DIAGRAM
LATCH SWITCH B
BOTTOM (OUTSIDE)
NOTE:
C
(SECONDARY)
Door is closed.
Unit is not operated.
+ Ground
zr Chassis
LOWER | UPPER
HEATER] HEATER
~
POWER
POWER
RELAY C
RELAY D
DIGITAL PROGRAMMER CIRCUIT
Lame!
POY
OVEN TEMP SENSOR
(OVEN THERMISTOR)
Oo
SHORT
SWITCH
HOODOO UOQDOOY Y
20
HIGH VOLTAGE
TRANSFORMER
ae HUMIDITY SENSOR
(NN~8808)
NOTE: When replacing, check the lead wire color as shown.
*Colors shown by (_) indicate colors of lead wire
connector housing.
SHORT SWITCH
BOTTOM (INSIDE)
POWER RELAY C
POWER RELAY B
POWER RELAY D
SYMBOL
PR | RED
GRAY
| 8 | BLACK
BL
W
Y
GR

NN-8508, NN-8558
NN-8808, NN-8858
NN-8808P
SCHEMATIC DIAGRAM (NN-8808P)
PLUG NOTE: Door is closed. MAGNETRON
ya a Unit is not operated.
< Ground
THERMAL
SWITCH A
CUTOUT (PRIMARY) zr Chassis
TURN
OVEN | TABLE | FAN oS
AGI20V LAMP | MOTOR] MOTOR’
Zz . 6
= O@ © |
LOWER | UPPER | SHORT S
HEATER] HEATER] SWITCH
LATCH! = —s pa
SWITCH B HIGH VOLTAGE
(SECONDARY) | TRANSFORMER
90
°o
0000000000009
POWER_ | POWER
RELAY 0 | RELAY C
[vssron a sees Scie cine
RELAY € : T ot RELAY B
-— 1 1 —
nies
(v)
o10a
010
| TRANSFORMER Pa se]
DIGITAL PROGRAMMER CIRCUIT Lemel Pan ; HUMIDITY SENSOR
OVEN TEMP SENSOR
(OVEN THERMISTOR)
This oven is equipped with automatic conversion system for both SOHz and 60Hz power supply
frequencies with a standard 115-120 volt supply.
No specific adjustment is necessary for conversion of the power supply frequency.
WIRING DIAGRAM NOTE: *When replacing, check the lead wire color as shown.
*Colors shown by (_ ) indicate colors of lead wire
connector housing.
LATCH SWITCH A POWER RELAY 8
| OR ORANGE |
| BR - BROWN |
PR | RED
| Bt BLACK |
LATCH SWITCH B SHORT SWITCH POWER RELAY C POWER RELAY D
BOTTOM (OUTSIDE) BOTTOM (INSIDE) / WHITE
BROWN
BR/W 1} /WHITE
Fig. 3

NN-8508, NN-8558
NN-8808, NN-8858
NN-8808P
DESCRIPTION OF OPERATING SEQUENCE
ON, OFF TIME ON
POWER RELAY B
ON (SEC) OFF (SEC)
1. Variable power cooking control
The
coil
of
power
relay
B
(RY
B)
is
energized
intermittently
by
the
digital
programmer
circuit,
when
the
oven
is
set
at
any
power
selec-
tion
except
for
High
power
position.
The
digital
programmer
circuit
controls
the
ON-OFF
time
of
power
relay
B
contacts
in
order
to
vary
the
output
power
of
the
microwave
oven
from
“Warm”
to
“High”
power.
One
complete
ON
and
OFF
cycle
of
power
relay
B
is
22
seconds.
The
relation
between
indications
on
the
control
panel
and
the
output
of
the
microwave
oven
is
as
shown
in
Fig.
4.
NOTE:
The
ON/OFF
time
ratio
does
not correspond
with
the
percen-
©
tage
of
microwave
power
since
approximately
1.5
seconds
are
required
for
heating
of
magnetron
filament.
2. Cyclic defrost
When Defrost power and defrosting time is siesta and Start pad is
tapped:
(A) The digital programmer circuit (DPC) divides the total defrosting time
into 8 cycles of alternating ON-OFF intervals of defrosting power and
standing periods. (See Fig. 5)
(B) During each defrosting period, power relay B is energized for 9
seconds and de-energized for 13 seconds by DPC. (See Fig. 6)
(C) During standing periods, power relay B is always open resulting in no
microwave power.
Approx Please refer to description
120W of cyclic defrost.
NOTE: Defrost time selected is converted into seconds by the DPC but
display will show selected time in minutes and seconds as prog-
rammed.
The
total
number
of
seconds
is
divided
into
8
time
TOTAL
DEFROSTING
TIME
periods.
The
remainder
(seconds
not
equally
divisible
by
8)
are
i)
18
1a vs
added
to
the
last
standing
time
period.
i
i
Example
:
if
defrosting
time
is
selected
for
5
minutes,
each
operating
period
will
be
as
follows
:
(See Fig.
7)
5
minutes
=
300
seconds
300/8
=
37
and
remainder
is
4
seconds.
The
4
seconds
is
added
to
the
last
time
period.
NOTE:
When
defrosting
time
is
selected
for not
more
than
7
seconds,
the
power
relay
B
will
not
be
energized
at
all.
OUTPUT POWER
INDICATION | AGAINST
HIGH POWER
mete
ao
Fig. 5
ONE DEFROSTING PERIOO(T/8)
aT
Fig. 6
S5MIN_(300SEC)
tsT 2ND 2ND LAST
STANDING( 37S) ,DEFROSTING(373) STANDING(373) STANDING( 443)
Fig. 7

NN-8508, NN-8558
3.
Auto
weight
defrost
control
When
the
Auto
Weight
Control,
Defrost feature
is
selected
and
the
Start
Pad
is
tapped:
(A)
The
digital
prograrnmer
circuit
determines
the
power
levels
and
de-
frosting
time
to
cormnplete
defrosting
and
indicates
the
operating
state
in
the
display
window.
Fig.
8
shows
the
defrosting
times
for
respective
weights
by
cate-
gories.
(B)
When
defrosting
time
in
the
display
window
has
elapsed,
the
oven
turns
off
automatically
by
the
controlled
signal
from
the
digital
prog-
rammer
circuit.
4. Auto reheat (NIN-8508/8558)
When
the
Auto
Reheat
Control
feature
is
selected
by
tapping
the
appropriate
key
pads
and
the
start
pad
is
tapped.
(A)
The
digital
programmer
circuit
determines
the
power
level
and
cook-
ing
time
to
complete
cooking
and
indicates
the
operating
state
in
the
display
window.
Fig.
9
shows
the
corresponding
cooking
times
with
respective
serving
by
categories.
(B)
When
cooking
time
in
the
display
window
has
elapsed,
the
oven
turns
off
automatically
by
a
controll
signal
from
the
digital
programmer
cir-
cuit.
NN-8808P
Auto Weight Defrost
SELECTED , DEFROSTING TIME
Auto Reheat (NN-8508/8558) nae
Roce
1
2 3
PASTRY
MEAT
CASSEROLE
ro een [aie rm ae
pa Poses | aint owe | in 0
Fig. 9
NN-8808, NN-8858

NN-8508, NN-8558
NN-8808, NN-8858
NN-8808P.
5. Baking and Broiling Control
FLAT HEATER
In this concept two (2) flat heaters are used. Located one on top and
one on bottom of oven cavity, they operate alternately to provide the
necessary heat. The heater consists of flat heater wire insulated be-
tween two mica plates similar to that of a toaster.
The digital programmer circuit controls the alternating ON-OFF time
of upper and lower heater in order to control the oven cavity tempera-
ture,
see
fig.
10A
and
11.
:
(A) After the start pad is tapped with the desired bake or broil program-
me selected, an 18V DC signal comes out of the digital programmer
circuit and is applied to the coil of power relay C and D alternately.
(B) When power relay C energizes, power source voltage (120V AC) is
applied to the upper heater and oven temperature starts increasing.
(C) When the power relay C is deenergized, upper heater turns off and
when power relay D is energized, the lower heater tums on.
In this way, the upper and lower heater tum on alternately until the
selected oven temperature is obtained.
(D) When the oven reaches the selected temperature, the digital prog-
rammer circuit senses the temperature through oven temp sensor and
stops supplying 18V DC signal to the power relays C and D resulting
in turn off of upper and lower heaters. After the heaters have been
turned off, the oven temperature will continue to increase a while then
decrease as shown in Fig. 11.
(E) When the oven temperature drops below selected temperature, the
digital programmer circuit senses the oven temperature and starts
supplying 18V DC to the coils of power relays C and D alternately
again.
NOTE 1: ON-OFF time of upper heater and lower heater vary depending
on the selected oven temperature as shown in Fig. 10A. When
baking Is selected with temperature setting of 200-450°F, off
period of both heaters is also programmed while oven temper-
ature is lower than selected temperature, as shown in Fig. 10A
and 11.
NOTE 2: When Broil cooking feature is selected, oven temperature is
determined automatically as shown in Fig. 10B.
Baking and Broiling
START
OVEN TEMP
OVEN TEMP
UPPER HEATER
(POWER RELAY C)
LOWER HEATER
(POWER RELAY D)
NOTE 3: ON-OFF time of upper heater and lower heater
vary depending on the selected oven temperature.
(See Fig. 11A.)
ie SELECTED OVEN TEMP
Heater ON-OFF Time for Preheat, Baking, Broiling
ON TIME OF | ONTIMEOF | OFF TIME OF
UPPER HEATER } LOWER HEATER) BOTH HEATERS
renee] | ries 05
Broiling Temperature :
CATEGORY OVEN TEMP .
Fig. 108
MAINTAINED OVEN TEMP.
NOTE 4: TU ---- ON time of upper heater
TL ---- ON time of lower heater
TF ---- OFF time of both heaters
Fig. 11

NN-8508, NN-8558
NN-8808, NN-8858
6.
Combination
cooking
control
Combination
cooking
is
accomplished
by
operating
the
microwave
and
heater
mode
alternately
during
one
combination
cooking
cycle.
One
combination
cooking
cycle
is
47
seconds.
-s
(A)
The
digital
prograrnmer
circuit
generates
the
power
relay
B,
C,
D
and
E
control
signals
at
a
specific
timing
as
shown
in
Fig.
12.
(B)
When
the
oven
ternperature
reaches
the
predetermined
temperature,
the
digital
programmer
circuit
stops
supplying
power
relay
C
and
D
control
signals
resulting
in
both
upper
and
lower
heaters
to
turn
off.
During
this,
digital
programmer
circuit
continues
supplying
power
re-
lay
B
and
power
relay
E
control
signals
so
that
microwave
and
fan
motor
activity
continues
at
predetermined
duty
ratio
as
shown
in
Fig.
12.
The
microwave
and
fan
motor
activity
continues
to
cycle
until
en-
tire
cooking
programme
is
completed.
(C)
When
the
oven
temperature
drops
below
the
predetermined
temper-
ature,
the
digital
programmer
circuit
generates
power
relay
C
and
D
control
signals
again
at
the
timing
predetermined.
NOTE:
The
power
relays
B,
C
and
D
do
not
tum
on
at
the
same
time.
Any
of
two
power
relays
of
them
should
be
always
off
so
that
in-
put
current
always
remains
within
allowable
main
current
(15A).
NN-8808P
Combination
Cooking
(When
combination
category
1
is
selected.)
START
OVEN TEMP
UPPER HEATER
(POWER RELAY C)
1
LOWER HEATER Lipeee
(POWER RELAY D)
FAN MOTOR
(POWER RELAY E)
MICROWAVE
(POWER RELAY B)
NOTE: ON-OFF time of upper heater, lower heater and microwave
vary depending on the selected combination category.
7.
Auto
weight
combination
cooking
control
When
the
Auto
Weight
Control,
Combination
Cooking
feature
is
selected
by
tapping
the
appropriate
key
pads
and
Start
pad
is
tapped.
(A)
The
digital
programmer
circuit
determines
the
power
level,
oven
temperature
and
combination
cooking
time
to
complete
combination
cooking
and
indicates
the
operating
state
in
the
display
window.
Fig.
13
shows
the
combination
cooking
times
for
respective
weights
by
categories.
(B)
When
the
combination
cooking
time
in
the
display
window
has
elapsed,
the
oven
turns
off
automatically
by
the
controlled
signal
from
the
digital
programmer
circuit.
Auto Weight Combination
SELECTED CATEGORY 1
Fig. 13

NN-8508, NN-8558
NN-8808, NN-8858
NN-8808P
AUTO SENSOR EXPLANATION, K FACTORS AND POWER LEVELS
(For NN-8808, NN-8858, NN-8808P)
1. Auto sensor cooking
Auto sensor cooking is a revolutionary way to cook by microwave with-
out setting a power level or selecting a time.
All that is necessary is to select an Auto Sensor Program before start-
ing to cook.
Understanding Auto Sensor Cooking
As a food cooks, a certain amount of steam is produced. If the food is
covered, this steam builds up and eventually escapes from the con-
tainer. In Auto Sensor Cooking, a carefully designed instrument, cal-
led the humidity sensor element, senses this escape of steam. Then,
based upon the Auto Sensor Program selected, the unit will automati-
cally determine the correct power level and the proper length of time
it will take to cook the food.
NOTE: Auto Sensor Cooking is successful with the foods and recipes
found in the Auto Sensor Cooking Guide. Because of the vast
differences in food composition, items not mentioned in the
Cooking Guide should be prepared in the microwave oven using
power select and time features. Please consult Variable Power
Microwave Cookbook for procedures.
Explanation of the Auto Sensor Cooking process (See Fig. 14A)
1) The shaded columns in Fig. 14A indicate when the humidity sensor
heater is on.
2) During the first 30 period there is microwave activity at Pi power.
This period is included to T1 time. During the next 30 second period is
no microwave activity. When calculating the T2 time, by using the for-
mula below, make sure this 30 seconds is subtracted from TO time.
3) T1 time:-:--The total amount of time it takes the microwave oven to
switch to T2 time. During this time one of the Auto Senser programs
will be shown in display.
4) T2 time-----When the steam escapes from the cooking container
placed in the oven, the humidity sensor detects it and the microp-
rocessor calculates the balance of cooking time. This T2 time is then
shown in the display and begins counting down.
Balance of cooking time (T2 time)
The balance of cooking time which is called T2 time, can be calcu-
lated by the following formula.
T2 time (in sec.) =T1 time X K factor
NOTE: Remember, the T1 time starts after the 50 second period. The
coefficient K is programmed into the microprocessor memory
and they are listed in the following tables along with the P1 and
P2 powers. (See Fig. 14B)
Some examples of calculating the T2 time
Example 1: If the T1 time is measured to be 2 minutes and 40 seconds
and the Auto program selected is COOK 6:
T2=T1i XK
= 2 min. and 40 sec. X 0.1
= 160 sec. X 0.1
= 16 sec.
2. Auto Sensor Reheat
With Auto Sensor Reheat, you can accurately reheat foods in accord-
ance with their current state of preparation. This allows you to set the
oven to reheat either: 1) Room temperature foods, 2) Refrigerated
foods and 3) Frozen foods at their appropriate power levels and times.
Best of all, Auto Sensor automatically does it all at the touch of a
button!
NOTE: The Auto Sensor Reheat process is same as Auto Sensor Cook-
Ing process. (See Fig. 14A)
15 SEC!
AUTO SENSOR COOK
CATEGORY
Pe [wee [we [a
Pe fee [ow [ee
Fig. 14B
AUTO SENSOR REHEAT
P1 P2 K factor
CATEGORY
es
Fig.14C

NN-8508, NN-8558
NN-8808, NN-8858
NN-8808P
CAUTIONS TO BE OBSERVED WHEN TROUBLESHOOTING
Unlike
many
other
appliances,
the
microwave
oven
is
high-voltage,
high-current
equipment.
Though
it
is
free
from
danger
in
ordinary
use,
.
extreme
care
should
be
taken
during
repair.
CAUTION
Servicemen
should
remove
their
watches
whenever
working
close
to
or
replacing
the
magnetron.
1. Check the grounding
Do
not
operate
on
a
2-wire
extension
cord.
The
microwave
oven
is
designed
to
be
used
when
grounded.
It
is
imperative,
therefore,
to
make
sure
it
is
grounded
properly
before
beginning
repair
work.
2.
Warning
about
the
electric
charge
in
the
high
voltage
capacitor
(Fig.
15)
For
about
30
seconds
after
the
oven
is
turned
off,
an
electric
charge
remains
in
the
high
voltage
capacitor.
When
replacing
or
checking
parts,
remove
the
power
plug
from
the
outlet
and
short
the
terminal
of
the
high
voltage
capacitor
(terminal
of
lead
wire
from
diode)
to
chassis
ground
with
an
insulated
handle
screwdriver
to
discharge.
WARNING
There
is
high-voltage
present,
with
high-current
capa-
bilities
in
the
circuits
of
the
high
voltage
winding
and
filament
winding
of
the
high
voltage
transformer.
It
is
extremely
dangerous
to
work
on
or
near
these
circuits
with
oven
energized.
DO
NOT
measure
the
voltage
in
the
high
voltage
circuit
including
filament
voltage
of
magnetron.
WARNING
Never
touch
any
circuit
wiring
with
your
hand
nor
with
an
insulated
too!
during
operation.
3.
When
parts
must
be
replaced,
remove
the
power
plug
from
the
outlet.
4.
When
the
15
Amp
fuse
is
blown
due
to
the
operation
of
short
switch:
WARNING
When
the
15
Amp.
fuse
is
blown
due
to
the
operation
of
short
switch,
you
must
replace
latch
switch
A
and
short
switch.
For
U.S.A.
models,
also
replace
power
relay
B
when
the
continuity
check
reads
shorted
contacts (1-2).
(A)
This
is
mandatory.
Refer
to
page
23
for
the
necessary adjustments
for
these switches.
(B)
When
replacing
the
fuse,
confirm
that
it
has
the
appropriate
rating
for
these models.
(C)
When
replacing
faulty
switches,
be
sure
mounting
tabs
are
not
bent,
broken
or
otherwise
deficient
in
their
ability
to
hold
the
switches.
5.
Avoid
inserting
nails,
wire,
etc.
through
any
holes
in
the
unit
during
operation.
Never insert a wire, nail or any other metal object through the lamp
holes on the cavity or any other holes or gaps, because such objects
may
work
as
an
antenna
and
cause
microwave
leakage.
15A
FUSE
HIGH
VOLTAGE
CAPACI TOR
Touch chassis side first then short to the high voltage capacitor
terminal.
6. Confirm after repair Bes?
(A) After repair or replacement of parts, make sure that the screws of the
oven, etc. are neither loose nor missing.
Microwaves might leak if screws are not properly tightened.
(B) Make sure that all electrical connections are tight before inserting the
plug into the wall outlet.
(C) Check for microwave energy leakage. (Refer to procedure for
measuring microwave energy leakage on page 24.)

NN-8508, NN-8558
NN-8808, NN-8858
NN-8808P
-DISASSEMBLY AND PARTS REPLACEMENT PROCEDURE
1. Replacement of the magnetron
CAUTION
Servicemen should remove their watches whenever
working close to or replacing the magnetron.
(A) Discharge the high voltage capacitor. (See page 15)
(B) Remove 2 screws holding air guide A. (Fig. 16)
(C)
Remove
2
high
voltage
leads
from
filament
terminals.
(F,
FA)
(D)
Remove
4
screws
holding
the
magnetron.
(Fig.
16)
NOTE:
To
prevent
microwave
leakage,
tighten
mounting
screws
proper-
ly
making
sure
there
is
no
gap
between
the
waveguide
and
the
magnetron.
CAUTION
When connecting 2 filament lead wires to the mag-
netron terminals, be sure to connect the lead wires in
the
correct
position.
The
lead
wire
of
high
voltage
transformer
should
be
connected
to
“F
terminal”
and
the
lead
wire
from
high
voltage
capacitor
should
be
connected
to
“FA
terminal”.
(See
Fig.
16)
2.
citor.
(A)
Disconnect
2
lead
wires
from
fan
motor
terminals.
(Fig.
17)
(B)
Disconnect
2
lead
wires
from
fuse
holder
terminals.
(Fig.
17)
(C)
Disconnect
4
high
voltage
lead
wires
from
high
voltage
capacitor
ter-
minals. (Fig. 17)
(D)
Remove
4
screws
holding
fan
motor
and
orifice
assy
and
detach
the
orifice assy with fan motor from oven assy. (Fig. 18)
(E)
Remove
fan
blade
from
the
fan
motor
shaft
by
pulling
it
straight
out.
(F)
Separate
the
fan
motor
from
the
orifice
assy
by
freeing
2
catch
hooks
on the orifice assy.
To replace high voltage capacitor
(G) Remove 1 screw holding high voltage capacitor.
Replacement of the fan motor and high voltage capa-
AIR
GUIDE A
THERMAL
CUTOUT MAGNE TRON
roe /
C$
—\—
9
arp
te
my]
|
—— =s
Of
j
Fig. 16
FAN MOTOR
TERMINALS
15A
FUSE
HIGH
VOLTAGE
CAPACITOR
Fig. 17
Fig. 18

NN-8508, NN-8558
NN-8808, NN-8858
NN-8808P
3.
Replacement
of
the
digital
programmer
circuit
(D.P.C.)
and
membrane
key
board.
NOTE:
Be
sure
to
ground
any
static
electric
charge
built
up
on
your
body,
before
handling
the
D.P.C..
(A)
Disconnect
all
connectors
from
D.P.C..
(Fig.
19)
(B)
Disconnect
all
lead
wires
from
the
power
relay
B,
C
and
D.
(C)
Remove
1
screw
holding
the
escutcheon
base.
(Fig.
19)
(D}
Disconnect
flat
cable
of
membrane
switch
by
pushing
connector
lever
and
pull
it
(Fig.
20).
(E)
Remove
2
screws
holding
the
D.P.C..
(Fig.
20)
To replace membrane key board
(F)
Remove
escutcheon
bracket
from
escutcheon
base
by
freeing
4
catch hooks on the escutcheon base.
(G)
Peel
off
the
membrane
key
board
from
escutcheon
bracket.
NOTE
1:
The
membrane
key
board
is
attached
to
the
escutcheon
brack-
et
with
double
faced
adhesive
tape.
NOTE
2:
When
installing
new
membrane
key
board,
make
sure
that
the
surface
of
the
escutcheon
bracket
is
cleaned
sufficiently
so
that
any
problem
(shorted
contacts
or
uneven
surface)
can
be
avoided.
NOTE
3:
Make
sure
new
membrane
keyboard
is
aligned
to
the
left
and
lower
edges
of
the
escutcheon
bracket.
(Fig.
21)
4.
Replacement
of
the
low
voltage
transformer
and/or
Fig.
19
power
relays
(RY
A,
RY
B,
RY
C,
RY
D,
RY
E)
(Fig.
20)
NOTE:
Be
sure
to
ground
any
static
electric
charge
built
up
on
your
body
before
handling
the
D.P.C.
(A)
Using
solder
wick
or
a
desoldering
tool
and
30W
soldering
iron,
care-
fully
remove
all
solder
from
the
terminal
pins
of
the
low
voltage
trans-
former
or
power
relays
(RY
A,
RY
B,
RY
C,
RY
D,
RY
E).
CN
5
NOTE:
Do
not
use
a
soldering
iron
or
desoldering
tool
of
more
than
30
Low
watts
on
D.P.C.
board.
VOL
TAGE
(B)
With
ail
the
terminal
pins
cleaned
and
separated
from
D.P.C.
con-
TRANSFORMER
tacts,
remove
the
defective
transformer/power
relay
and
install
new
transformer/power
relay
making
sure
all
terminal
pins
are
inserted
completely.
Resolder
all
terminal
contacts
carefully.
Fig. 20
ESCUTCHEON
BRACKET
MEMBRANE
KEY BOARD
LEFT €DGE
LOWER EDGE
Fig. 21

NN-8508, NN-8558
NN-8808, NN-8858
NN-8808P
5. Disassembly of the door assembly.
(A)
Open
the
door
and
remove
4
screws
holding
door
C.
(Fig.
22)
(B)
Remove
the
door
C
from
door
E
by
carefully
pulling
outward
starting
from
upper
right
hand
corner.
(Fig.
22)
(C)
Remove
door
key
spring
and
remove
3
screws
holding
door
handle.
(Fig.
23)
(D)
Separate
the
door
A
from
the
door
E
by
freeing
6
catch
hooks
on
the
door
A.
(Fig.
24)
(E)
Remove
door
keys,
door
key
lever,
door
key
spring
and
door
key
pins. (Fig. 23)
Fig. 22
a ee
DOOR KEY A
DOOR KEY
LEVER
DOOR KEY
SPRING
Fig. 23
Fig. 24

NN-8508, NN-8558
NN-8808, NN-8858
NN-8808P
6.
Replacement
of
the
upper
heater
(Heater
B)
(A)
Release
humidity
sensor
wires
from
3
lead
wire
holders
and
discon-
nect
sensor
connector
from
D.P.C..
(B)
Remove
2
nuts
holding
2
heater
terminals.
(Fig.
25)
(C)
Remove
a
screw
holding
heater
terminal
plate
bracket.
(D)
Remove
2
screws
holding
heater
panel
A
and
lift
off
the
panel.
(E)
Remove
4
screws
holding
inner
heater
panel
and
lift
out.
(Fig.
26)
(F) Remove adiabatic material B.
(G)
Remove
the
upper
heater
(heater
B)
by
carefully
freeing
the
2
hooks
holding
the
center
portion
of
heater
and
removing
2
screws.
(Fig.
27)
NOTE
:
Special
screws
are
used
to
hold
the
inner
heater
panel
and
hea-
ter
B.
(Fig.
26
&
27)
;
OUTER HEATER HEATER TERMINAL
PLATE BRACKET
HEATER
TERMINALS
Fig. 25
SPECI AL
SCREWS
(FRONT)
INNER HEATER PANEL
Fig. 26
UPPER HEATER
Fig. 27

NN-8508, NN-8558
NN-8808, NN-8858
NN-8808P
7. Replacement of the lower heater (Heater A)
(A) Remove the tray and the turntable from oven cavity.
(B) Carefully turn the oven up side down.
(C) Remove the base C by removing 2 screws. (Fig. 28)
(D) Disconnect the turntable motor connector.
(E) Remove 2 screws holding 2 heater terminalis. (Fig. 29)
(F) Remove the motor bracket by removing 3 screws. (Fig. 30)
(G)
Remove
the
lower
heater
panel
by
removing
5
screws.
(Fig.
34)
(H) Remove the adiabatic material A.
(I) Remove the lower heater (heater A) by freeing the 4 hooks and re-
moving 2 screws. (Fig. 35)
Fig. 28
TURNTABLE
MOTOR
MOTOR
BRACKET
HEATER TERMINALS
Fig. 29
LOWER HEATER PANEL
HEATER
TERMINALS
LOWER HEATER
(HEATER A)
Fig. 31 Fig. 30