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13

YES

YES

YES

NO

NO

NO

Can the DTMF
sound be monitored?

Does the DTMF signal
appear at base of Q424?

Check Q424,Q108.

Does the DTMF signal
appear at Pin62 of IC801?

Check
R482, C481 and Q406, D401.

Check
R921, R922, R923, R924, 
R925 and C923.

Check IC801, X801 and X802.

YES

YES

YES

YES

NO

NO

NO

NO

Call the unit from
another telephone.

Does a sine wave of
approximately 60V or more
appear across Tip and Ring?

Check the telephone line
and the telephone line cord.

Is the voltage at the anode
and cathod of D1 30V?

Check C1, C2, R1, D1, D2,  
D3, D4, D5 and D6

.

Is the voltage across Pins 1
and 5 of IC1 30V

Check IC1.

Does the tone ringer
output signal appear
across Pin 8 and 5 of IC1?

Check
IC1, R2, R3,  R4, C3 and C5.

Check the SW1, Q1 and T1.

14

Ref. No.

Procedure

Shown in Fig —.

To remove —.

Remove —.

1

1

1

Lower Cabinet

Screws (2.6

× 12) . . . . . . . . . . . . . (A)× 5

2

1 ~ 2

2

Printed Circuit Board

Remove the P.C.Board

Remove the P.C. Board

Fig 1

Fig 2

When assembling,
check the boss
inserted completely

A

15

Vcc 1

RSL 2

LFI 3

LFO 4

OUT

8

HFI

7

HFO

6

GND

5

LOW FREQ
OSC

HIGH FREQ
OSC

POWER SUPPLY

WITH

HYSTERISIS

AMP

Pin descriptions

1

2

3

4

5

6

7

8

Vcc

RSL

LFI

LFO

GND

HFO

HFI

OUT

Power supply pin

   RSL pin

Low-frequency time

constant connector pin

 GND pin

High-frequency time

constant connector pin

Output pin

This is the power supply pin for the lC. It is connected to the (     ) pin of the diode bridge.

This is used to change the operation initiation current when connected to the GND pin.

This is connected to the time constant that determines the oscillation frequency
on the warble.

This pin has the lowest potential on the lC. It is connected to the (     ) pin of the diode bridge.

This is connected to the time constant that determines the oscillation frequency
on the tone side (the audible frequency side).

This is used to connect a piezoelectric buzzer, or to connect a dynamic speaker through a 
transformer.

16

Even if you do not have the special tools (for example, a spot heater) to remove the Flat IC, with some solder (large amount), a
soldering iron and a cutter knife, you can easily remove the ICs that have more than 100 pins.

• PbF (: Pb free) Solder
• Soldering Iron

Tip Temperature of 700 

° F ± 20 ° F (370 ° C ± 10 ° C)

Note: We recommend a 30 to 40 Watt soldering iron. An expert may be able to use a 60 to 80 Watt iron where someone with
less experience could overheat and damage the PCB foil.

• Flux

Recommended Flux: Specific Gravity 

→ 0.82.

Type 

→ RMA (lower residue, non-cleaning type)

Note: See About Lead Free Solder (Pbf: Pb free) (P.4)

1. Put plenty of solder on the IC pins so that the pins can be completely covered.

If the IC pins are not soldered enough, you may give pressure to the P.C. board when cutting the pins with a cutter.

2. Make a few cuts into the joint (between the IC and its pins) first and then cut off the pins thoroughly.

3. While the solder melts, remove it together with the IC pins.

When you attach a new IC to the board, remove all solder left on the board with some tools like a soldering wire. If some solder is
left at the joint on the board, the new IC will not be attached properly.