Furuno 42a12d Manuales De Servicio

03-TM-0038 REV 00 PAGE 5 of 5

3.3.3.  ADJUSTING FREQUENCY RANGE.
A.  The frequency range for the Test Set is 30 to 45 kHz.
The audio output is tuned for approximately 3200 Hz.

B.  Set the TUNING knob to the maximum frequency (45
kHz).  Place an oscilloscope probe or frequency counter on
the output of the local oscillator circuit, pin 14 of U2.  See
Figure 3.3.

C.  Monitoring the frequency, adjust R16 for the maximum
L.O., approximately 42 kHz or as high as possible.

D.  Set the TUNING to the minimum frequency (30 kHz).

E.  Tune R22 for the minimum L.O., approximately 27 kHz.

F.  Repeat steps C through E as many times as necessary
until both ends are tuned.

Figure 3.2. is the schematic diagram for the 42A12D Ultra-
sonic Test Set.

A.  Tuning or Gain
      1 control knob....................P/N 809-440-0004
B.  GAIN control R13.......................P/N 601-315
C.  TUNING control R23..................P/N 601-372
D.  Battery.............................NEDA Type  1604A

BT1

9V

SW

1

SW

  POW

ER

R13

10K

C1

68

R1

33. 2K

R7

15K

R5

68. 1K

R6

221K

Q3

2N5086

C3

. 01

Q2

2N5088

R29

75K

R9

68. 1K

Q4

2N5088

C6

. 01

C15

. 01

R8

100K

L1

2. 7MH

R17

750

R19

75K

T2

1408

L2

2. 7MH

R30

2. 7

C10

68

C18

68

AUDI O OUTPUT

R31

10

R32

10

LS1

SPEAKER

J2

C11

10

C12

330

C13

68

C14

. 02

R20

10

C7

. 1

C9

. 047

R18

120

6

4

1

7

  5

    2

    3

8U?

LM386M

R11

6. 8

R10

47. 5K

R12

4. 75K

C8

22

C2

. 01

R3

3. 16K

R4

3. 32K

C4

22

D2

1N4005 T1

1408

Q1

2N5088

R2

150

D1

1N4005

Y1

TRANSDUCER

R24

2. 00K

D4

1N4454

D3

1N4454

R28

7. 15K

  12

  13

14

4

1

1

U2D

LF444

R27

22. 6K

    5

    6

  7

4

1

1

U2B

LF444

C17

470pF

R26

56. 2K

R25

56. 2K

  10

    9

  8

4

1

1

U2C

LF444

R22

10K

R15

511K

R14

511K

C5

560pF

    3
    2

  1

4

1

1

U2A

LF444

C16

. 1

R23

100K

R16

50K

R21

47. 5K

UNLESS  OTHERW

I SE  SPECI FI ED;

1.   ALL  RESI STORS  ARE  I N  OHMS,   K=1, 000,

2.   CAPACI TORS  ARE  I N  MICROFARADS.

M=1, 000, 000,   1/ 3  W

ATT  +/ -   1%.

NOTES: