19.1. High voltage transformer
1. Remove connections from the transformer terminals and
check continuity.
2. Normal (cold) resistance readings should be as follows:
Secondary winding Approx. 80
Ω
—120
Ω
Filament winding Approx. 0
Ω
Primary winding Approx. 0
Ω
—3
Ω
19.2. High voltage capacitor
1. Check continuity of capacitor with meter on highest OHM
scale.
2. A normal capacitor will show continuity for a short time, and
then indicate 9M
Ω
once the capacitor is charged.
3. A shorted capacitor will show continuous continuity.
4. An open capacitor will show constant 9M
Ω
.
5. Resistance between each terminal and chassis should be
infinite.
19.3. Magnetron
Continuity checks can only indicate an open filament or a
shorted magnetron. To diagnose for an open filament or
shorted magnetron.
1. Isolate magnetron from the circuit by disconnecting the
leads.
2. A continuity check across magnetron filament terminals
should indicate one ohm or less.
3. A continuity check between each filament terminal and
magnetron case should read open.
19.4. Diode
1. Isolate the diode from the circuit by disconnecting the leads.
2. With the ohmmeter set on the highest resistance scale,
measure the 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 resistance of the
diode, otherwise an infinite resistance may be read in both
directions.
A normal diode's resistance will be infinite in one direction
and several hundred k
Ω
in the other direction.
19.5. Membrane key board
(Membrane switch assembly)
Check continuity between switch terminals, by tapping an
appropriate pad on the key board. The contacts assignment of
the respective pads on the key board is as shown in digital
programmer circuit.
19.6. Protector diode
1. Isolate the protector diode assembly from the circuit by
disconnecting its leads.
2. With the ohmmeter set on the highest resistance scale,
measure
the
resistance
across
the
protector
diode
terminals.
Reverse the meter leads and again observe the resistance
reading. A normal protector diode's resistance will be
infinite in both directions. It is faulty if it shows continuity in
19 COMPONENT TEST PROCEDURE
30
NE-1257R/NE-1257CR / NE-1757R/NE-1757CR / NE-2157R/NE-2157CR / NE-1258R
Summary of Contents for NE-1257CR
Page 4: ...1 OUTLINE DIAGRAM 4 NE 1257R NE 1257CR NE 1757R NE 1757CR NE 2157R NE 2157CR NE 1258R ...
Page 5: ...2 OPERATION PROCEDURE 5 NE 1257R NE 1257CR NE 1757R NE 1757CR NE 2157R NE 2157CR NE 1258 ...
Page 6: ...6 NE 1257R NE 1257CR NE 1757R NE 1757CR NE 2157R NE 2157CR NE 1258R ...
Page 7: ...7 NE 1257R NE 1257CR NE 1757R NE 1757CR NE 2157R NE 2157CR NE 1258 ...
Page 8: ...8 NE 1257R NE 1257CR NE 1757R NE 1757CR NE 2157R NE 2157CR NE 1258R ...
Page 9: ...9 NE 1257R NE 1257CR NE 1757R NE 1757CR NE 2157R NE 2157CR NE 1258 ...
Page 34: ...34 NE 1257R NE 1257CR NE 1757R NE 1757CR NE 2157R NE 2157CR NE 1258R ...
Page 35: ...22 TROUBLESHOOTING GUIDE 35 NE 1257R NE 1257CR NE 1757R NE 1757CR NE 2157R NE 2157CR NE 1258 ...
Page 47: ...47 NE 1257R NE 1257CR NE 1757R NE 1757CR NE 2157R NE 2157CR NE 1258 ...