Kenwood TR-7400A - TROUBLESHOOTING; Receiver Malfunctions

Malfunction in Receiver
Malfunction in Others
Remedy
Set squelch to
OFF.
Set itto OFF.
Check voltages.
Check
Check
Check
Readjustment
Replacement
Readjustment
Symptom
(1) No noise.
(2) Low sensitivity
Cause
Squelch in ON setting.
Tone switch
set to tone squelch position.
Malfunction in audio circuit.
Speaker lead wires defective. (in particular, connecting parts).
Ear phone jack broken.
Antenna system defecitve (M-type connector, antenna wires,
etc.)
RF cavity tuning shifted.
D6 defective in VCO unit.
Improper adjustment for L9 in RX unit.
(3) Defective deflection at S
meter.
(4) Noise generated, but recep-
tion impossible.
Remedy
Check
Replacement
Replacement
Check
Check
Check
Provide fuses.
Check
Replacement
Check.
Symptom
(1) F display LED not lit or
letter trouble.
\
(2) No power supply.
(3) Fuses blowing out.
Cause
No 5V AVR output
LED defective.
Driving IC (IC1
- IC3) defective.
Rotary switch for F in trouble.
Poor contact around sockets in display and LED printed
circuit boards.
Poor contact between pin and connector with lead wire of
display printed circuit board.
No fuse in fuse holder.
Disconnection or improper soldering in power cable.
Power switch broken.
Power circuit connected reversely.
Meter defective.
Improper adjustment for VR1 for meter sensitivity adjustment.
10.245 MHz (L1 1) crystal defective.
Each TR defective in receiver (RF and IF stages).
Improper adjustment for each coil in receiver (RF and IF stages).
Replacement
Readjustment
Replacement
Replacement
Readjustment
(5) Squelch malfunction.
(6)
Zzz.. . noise generated with
squelch switched ON and
in the mode of TX
+ RX.
(7) Tone squelch malfunction
(in RX setting).
(8) Howling caused near AF
VR MAX.
(9) Howling near AF VR
MAX.
Tone squelch set to ON position.
Noise amplifier malfunction or 012,013 defective in RX unit.
Improper adjustment for VR2 in RX unit.
Set it to OFF.
Replacement
Readjustment
Dl 5 defective in
RX unit.
lmproper insertion of printed circuit board of active filter in
RX unit.
011, 019
- 21, or Dl 1 - Dl4 defective in RX unit.
Insufficient tightening of bolts for case, printed circuit boards,
speaker, etc.
C16 coming too close to C22 in VCO unit.
VCO coil is loose on coil form.
Replacement
Check
Replacement
Check
Separate them.
Reseal with
glue.