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5

Changed from the Original Service Manual section 12.3.23.1.

Check the following parts first: F1, F101, RC1, C2, Q1 and IC1.
This comes from our experience with experimental test. For example: power supply and lightning surge voltage test, with standing
voltage test, intentional short circuit test, etc.
Caution:

If you find a melted fuse in the unit, do not turn on the power until you located and repair the faulty parts (except for the fuse);
otherwise the fuse will melt again and you cannot pinpoint the faulty point.

In most cases, the symptom is that nothing is output. It is more likely that the fault is in the primary side rather than the secondary
side. Check the primary side first.

: Volt Meter

7 +24V

3 +12V

2 HTRCTL

1 NC

6 +24V

5 GND

4 GND

V

21.6V-27.6V

V

6.5V-13.2V

220

4W

120

3W

V

When you check voltage in
a power supply unit alone,
use this dummy load.
If the dummy load is not
available, connect the main
P.C.B. to the analog P.C.B.

Input
Circuit

AC
Input

RC1

VDD

G

H

24V

Kick-on
Voltage
Circuit

E

F

12V

HTRCTL

GND

Control
Circuit

Converter
Circuit

C

D

Rectifier
Circuit

A

B

+

Error Detecting
Circuit  PH1

O.C.P

O.L.P

Q1

A-B Voltage Wave Form

C-D Voltage Wave Form

E-F

G-H Voltage Wave Form

0

0

0

T1

Triac
CR1

Heat Lamp

Photo Triac
Coupler  PHT1

+

+

C2

6

Changed from the Original Service Manual section 12.3.23.3.

(RC1)
If RC1 is short-circuit, F1 will melt (open).
In this case, replace the parts (RC1 and F1).
(Q1)
The worst case of Q1 is a short-circuit between the Drain and Gate because damage expands to the peripheral
circuit of Q1. This is due to a very high voltage through the Gate circuit, which is composed of IC1. You should
change all of the parts listed as follows. 

• F1, Q1, IC1

(C2)
If over voltage (more than AC320V) was supplied for a Low Voltage Power Supply board (SMPS Board), C2 will be broken. 
(F2)
If F2 is melted (open), check the 24V lines of the Main board and others. 

7

Changed from the Original Service Manual section 16.11.

L1

L6

F

101

R1
8

R2
1

R2
0

RC

2

T1

Z1

C1

R1
1

A

IC
1

Q1

C9

L2

R2
B

R2
A

R1
A

R1
B

1

8

2

3

4

5

6

7

3

4

R1
1

B

R7

R5

D6

R6
B

R6
A

D5

C4

C8

R3

C5

C6

C7

PH

1

IC
2

R1
9

C1
3

R2
4

R2
2

C1
0

A

(R
2

8

)

PH

1

(C
2

6

A

)

(C
2

6

B

)

F1

R4
2

R4
3

CR

1

C2
7

C2
8

PH

T

1

2H

T

R

C

T

L

GN

D

PH

T

1

C3

5

1

CN

2

+2
4

V

GN

D

RC

1

D1
0

C1
5

R2
5

C1
1

C1
2

NC

7

6

CN

3

1

3

F2

R4
1

TH
1

C2

R4

(C
1

4

)

Ir

a

te

d

=

2

.4

A

Ip

e

a

k

=

3

.6

A

+1
2

V

Ir

a

te

d

=

0

.7

5

A

Ip

e

a

k

=

0

.8

0

A

R2
9

A R2

9

B

R2
9

C

CN

1-

L

(Q
2

)

DZ
1

(D
Z

2

)

R3
0

AC

 O
U

T

(D
1

1

)

(R
1

0

)

(C
2

9

)

(D
1

2

A

)

(D
1

2

B

)

R3
1A
,B

,

(R
3

2

)

L3

C1
6

CN

1-

N

(TB

1

)

(L
5

)

(C17

)

(C
1

9

)

(C
2

0

)

(C
1

8

)

(L
4

)

(2

2

k

Ω

)

(3

.6

k

Ω

)

(C
),

(D
),

(E

)

8

Changed from the Original Service Manual section 17.6.