Teac A-400 Service Manual page 23

6. TROUBLE-SHOOTING
NOTE
REF. NOQ's indicated in the following table refer to the left
channel, for the right channel REF. NO. identification, see
schematic diagram.
TAPE TRANSPORT SECTION
1. Fuse blows when POWER is switched ON
— Defective Power Transformer
2. Auto End-stop will not work in Play and/or Fast Wind.
Sound cannot be heard during recording.
— Defective Transistor 0101, 0102, 0103, 0104, 0105
— Defective Dolby IC Unit
— Defective Parts associated with parts indicated above
. Level Meter will not indicate in playback mode.
+B voltage not present between terminal A of SCR and GND.
— Defective Resistor R313
— Defective Diode D310
Solenoid will not energize when SCR terminals A and K are
switched ON.
~— Defective Switch $408
— Defective Solenoid
Solenoid will not work when SCR terminals A and G are shorted
together. .
— Defective SCR
3. Tape winds onto Capstan Shaft.
— Defective Pinch Roller
~ Defective Take-up Reel Table Assy
— Idler slipping
— Tape path wrong (improper Tape Guide position bad
Head mounting)
4. Excessive Wow and Flutter
— Defective Pinch Roller, Pinch Roller pressure incorrect
— Capstan Belt stretched or oily
5. Capstan does not rotate
— Capstan Belt off
— Defective Motor
6. Index Counter will not count
— Counter reset button not fully depressed.
— Counter Belt off
AMPLIFIER SECTION
1. No sound in playback mode
Noise (hum or clicking noise) appear when touching head wires.
— Poor soldering of head terminations
— Defective Head .
Sound can be heard. during-recording
— Defective Switch $101
— Defective Transistor 0103, 0104
—. Defective Parts associated with parts indicated above
— Defective Level Meter
Defective Transistor 0108
Defective Semi-fixed Resistor VR103
Defective Parts associated with parts indicated above
. Loss of high frequencies in playback mode
High frequencies too low
— Defective Transistor 0102
— Playback equalizer circuit wrong
High frequencies are several dB below specified response limits
— Head dirty or defective
Loss of high frequencies including level variation
~ Improper head-to-tape contact
— Unstable functioning of tape transport mechanism
. Poor playback signal-to-noise ratio
Excessive hum — gets better when Capacitor C108 is removed.
— Defective Head
Excessive hum —.reduced when changing Record/Playback PC
Board's location
— Defective Power Transformer
Excessive white noise (hiss and circuit noise)
— Defective Head :
— Defective Transistor 0103, 0104
— Associated circuitry of Transistor 0103, 0104
Wave form varies continuously
— Defective Transistor 0103, 0104
— Defective Capacitor C109, C113
— Defective Parts associated with parts indicated above
. Does not record
Can record when changing Bias Switch setting
— Defective Bias Switch
— Defective Semi-fixed Resistor VR104, VR105
— Defective Parts associated with parts indicated above
Cannot erase, also
— Bias Oscillator Assy faulty
Can erase — sound from record monitor mode is normal
— Head dirty
— Defective Transistor 0107
— Defective Switch $101
~ Defective Circuitry of 0107, $101
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