TU 940 - Harman Kardon Audio Service Manual (repair manual)

LEAKAGE TEST…………………………...…2

SPECIFICATIONS…………………………....3
CONTROL AND FUNCTIONS………………4
BLOCK DIAGRAM……………………………7

DISASSEMBLY PROCEDURES……………8
CIRCUIT DESCRIPTION…………………..13

ALIGNMENT PROCEDURES……………..16

GENERAL UNIT EXPLODED VIEW..…….21

PRINTED CIRCUIT BOARDS…………..…22
ELECTRICAL PARTS LIST……………......24
IC FUNCTIONAL BLOCK DIAGRAM……..32

PACKAGE……………………………………33
WIRING DIAGRAM…………………………35

SCHEMATIC DIAGRAMS………..………..36

                                         

          harman/kardon

Parts and Service Office

80 Crossways Park West, Woodbury, N.Y. 11797

                                                            Printed in Korea

LOCAL DX

RDS PTY RT CT TA EON TUNED STEREO

MONO TUNING

PRESET

RF LEVEL

STANDBYWIDE

NARROW

CLOCKTIMERON OFF SLEEPAUTOMEMORYSCAN

Power

1

2

3

4

5

6

7

8

9

0

Band

Auto/Man

IF Band

Display

Mode

Memory

TU 940 RDS

Tune/Pst

Pst Scan

Remote sensor

Display

PTY

Direct

Character

Tuning

RF Mode FM Mode

Before returning the unit to the user, perform the
following safety checks:
1. Inspect all lead dress to makes certain that leads

are not pinched or that hardware is not lodged
between the chassis and other metallic parts in the
unit.

2. Be sure that any protective devices such as

nonmetallic control knobs, insulating fishpapers,
cabinet backs, adjustment and compartment covers
or shields, isolation resistor-capacity networks
mechanical insulators, etc. Which were removed for
servicing is properly reinstalled.

3. Be sure that no shock hazard exists; check for

leakage current using Simpson Model 229 Leakage
Tester, standard equipment item no. 21641, RCA

model WT 540A or use alternate method as follows:
plug the power cord directly into a 230-volt AC
receptacle ( do not use an isolation transformer for
this test.). Using two clip leads, connects a 1500
ohm, 10-watt resistor paralleled by a 0.15  µF
capacitor, in series with all exposed metal cabinet
parts and a known earth ground such as a water
pipe or conduit. Use a VTVM or VOM with 1000
ohms per volt, or higher sensitivity to measure the
AC voltage drop across the resistor. (This test
should be performed  with the power switch in both
the on and off positions.)
A reading of 0.35 volt RMS or more is excessive
and indicates a potential shock hazard which must
be corrected before returning the unit to the owner

       

Test Condition: 40 kHz DEV., 1kHz Frequency.
Tuning Range/Step                  87.5 MHz –108 MHz/50 kHz
Usable Sensitivity (-26dB S/N)

  Mono                  

[

 8.15 dBf        

[

 12.25 dBf

Limiting Sens at –3 dB     

[

 7.2 dBf         

[

 9.2 dBf

50dB Quieting Sens
  Mono                  

[

 16.2 dBf        

[

 19.2 dBf

  Stereo                 

[

 39.2 dBf        

[

 42.8 dBf

Total Harmonic Distortion

  Mono                  

[

 0.1%           

[

 0.25%

  Stereo                 

[

 0.15%          

[

 0.35%

Signal to Noise Ratio (1mV RF INPUT)
  Mono                  

〈

 80 dB           

〈

 75dB

  Stereo                 

〈

 75 dB           

〈

 70 dB

Stereo Separation at 98 MHz ( NORMAL)

1kHz                  

〈

 50 dB           

〈

 40 dB

10kHz                 

〈

 40 dB           

〈

 35 dB

Muting and Automatic Tereshold at 98 MHz

                        31.2 

6

 2 dBf        31.2 

6

 4 dBf

Auto Stop Level          31.2 

6

 2 dBf        31.2 

6

 4 dBf

Selectivity NORMAL/NARROW  

6

 300 kHz

                         

〈

 50/70 dB         

〈

 34/60 dB

Auto Scan Error           

6

 15 kHz          

6

 20 kHz

Frequency Response at 30 Hz –15 kHz

                          

6

 0.5 dB          + 1/

2

2.5 dB

Image Rejection at 106 MHz   

〈

 80 dB         

〈

 65dB

AM Suppression             

〈

 60 dB          

〈

 50 dB

RDS Sensitivity          31.2 

6

 2 dBf        31.2 

6

 4 dBf

Output Voltage

  Mono                 500

6

100mV        500

6

150mV

⋅ H ⋅ D)                   442 

⋅

 92 

⋅

 350

WEIGHT                                 3.9 Kg

POWER SUPPLIES                       AC 230 V, 5-Hz
POWER CONSUMPTION                  15W

These specifications are service target specs.
Specifications and components are subject to change without notice.
Overall performance will be maintained or improved.

             

Test Condition: 400 Hz, 30% Modulation
Tuning Range/Step
  MW                522 kHz – 1611 kHz/9 kHz

Usable Sensitivity (

2

 20 dB S/N)

  MW: 594 kHz, 1404 kHz      

[

 500 mV            

[

 800 mV

Signal to Noise Ratio (0.1 V INPUT)
   MW: 999 kHz               

〈

 55dB              

〈

 48 dB

Frequency Response at 

2

 6 dB

   MW                     160 Hz ~ 2.5 kHz    150 Hz ~ 2 kHz

Selectivity at 

6

 9 kHz

   MW: 999 kHz               

〈

 35dB               

〈

 30 dB

A.G.C. Figure of merit at 999 kHz
                              

〈

 50 dB              

〈

 45 dB

Image Rejection

   MW: 1404 kHz              

〈

 40 dB              

〈

 35 dB

Total Harmonic Distortion ( 0.1 V INPUT)

    MW: 999 kHz              

[

 0.7%               

[

 1.2 %

Tuned Level

    MW: 999 kHz             800 mV 

6

 3 dB   800 mV 

6

 5 dB

Output Voltage ( 5mV INPUT)

                            165 

6

 30 mV       165 

6

 40 mV

1. POWER
Press to turn the unit on. The ring around the button will glow green. Press again to turn the unit
off. The ring will glow red and the word “STANDBY” will appear in the display.

2. NUMBERIC KEYS
Use to select the preset number of a station that has been entered into the preset memories or
to store a station in the memory in conjunction with MEMORY 

.

To recall a previously programmed station, press the appropriate numeric button(s). For single
digit numbers (1-9), press the number and the station will be tuned at once or in a few seconds.
To recall preset locations 10 though 30, press the desired buttons in order and the station will be
tuned at once.
To use the buttons to enter a station to the preset memory, see page 10.

3. FLUORESCENT DISPLAY
The display panel contains a large display for station frequency information and RDS data, as
well as status indicators for various tuner functions and 5-step RF level indicator bars.

4. BAND
Press to change between FM and AM frequency bands..

5. IF BAND (FM TUNING ONLY)
Press to change the passband of the intermediate frequency to compensate for interference
form adjacent station.
NARROE: When reception is disturbed by interference from other stations, press until
NARROW is lit. This improves reception.
NORMAL: For normal reception, press until NORMAL is lit.

6. DISPLAY MODE
Press to change between bright and dim display lighting or display off.

LOCAL DX

RDS PTY RT CT TA EON TUNED STEREO

MONO TUNING

PRESET

RF LEVEL

STANDBYWIDE

NARROW

CLOCKTIMERON OFF SLEEPAUTOMEMORYSCAN

Power

1

2

3

4

5

6

7

8

9

0

Band

Auto/Man

IF Band

Display

Mode

Memory

TU 940 RDS

Tune/Pst

Pst Scan

Remote sensor

Display

PTY

Direct

Character

Tuning

RF Mode FM Mode

4 5 6

7

8

9

10

11

12

14

13

15

16

17

3

2

1