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CASSETTE ALIGNMENT
INSTRUCTIONS
Equipment required: Double Beam Oscilloscope; Frequency Counter; RMS Meter;
Non-Metallic Trimming Tool; 6.8KHz Test Tape;
1kHz Test Tape.
FUNCTION
SIGNAL IN
SIGNAL OUT
METHOD
REMARKS
1
Bias frequency
Switch SW 301
to record.
Monitor 'scope or freq.
Adjust L303 to give 625KHz.
Ensure the AFC switch is off.
adjustment.
counter from junction
C328, C331.
2
Bias trap adjustment.
Switch SW 301 to record.
RMS Meter across
Adjust L301/302 to get the same
Voltage should not change if the
R301/302 in turn.
voltage at R301 & R302.
AFC sw is on or off.
3
Bias level adjustment.
Switch SW 301 to record.
RMS Meter across
Adjust VR 301/VR 302 to
Ensure AFC switchis off.
R301/302 in turn.
show 4.5mvV.
4
Head azimuth
6.8KHz Test tape.
Double beam 'scope at
Ensure set switched to tape.
adjustment.
speaker sockets.
5
Tape speed adjustment.
1KHz Test tape.
Frequency counter at
Ensure set switched to tape.
speaker socket.
Adjust azimuth screw for max
amplitude on both channels
ensuring both signals in phase.
Adjust motor with non-metallic
trimming tool for correct frequency.
CASSETTE
DECK MECHANISM - GENERAL
MAINTENANCE
Before attempting any specific fault-finding on the cassette mechanisms, it is recommended
that the
following checks and maintenance procedures be carried out.
1. R/P HEAD (Symbol 14)
Thoroughly clean the head and examine for signs of wear; replace if worn; de-magnetise.
2. PINCH-ROLLER
ASSEMBLY (Symbol! 12)
Thoroughly clean, check general condition.
if rubber roller is in any way distorted, replace the
assembly.
Check the tension of the Pinch-Roller Spring, the tension should be 40 to 60gm.
3. MAIN
BELT (Symbol 5)
Ensure the belt is correctly located.
Check that it is not stretched or worn and replace if necessary.
In
any event, remove the belt and clean with methylated spirits.
4. TAKE-UP SPOOL ASSEMBLY (Symbol 9)
Check the tension of this using a cassette torque meter.
The correct reading should be 40gm per cm.
A reading of between 30 and 50gm per cm may be regarded as within tolerance.
Should the reading fall below 30gm per cm, it must be adjusted to give the correct torque.
lf it cannot be adjusted it should then be replaced.
5. REWIND
IDLER ASSEMBLY (Symbol! 2)
Check the tension with the cassette torque meter using the rewind function.
The torque should be 100gm per cm but a reading of between 80 and 110gm per cm may be
considered within tolerance.
If the torque falls below 80gm per cm, it should be adjusted to give the correct reading.
If it will not adjust sufficiently, it should be replaced.
6. MOTOR
(Symbol! 1)
Ensure that the motor is securely mounted and that the motor rubbers are in good condition.
7. FLY-WHEEL (Symbol 6)
Check that the Fly-wheel spindle is not worn or bent and that it is securely seated in its bearing.
8. INTERNAL
MECHANISM
After prolonged use, the internal mechanism will normally contain substantial deposits of oxide dust.
Ensure that these are thoroughly cleaned.
There are no places on either mechanism which require any oil or grease and the application of any such
lubrication is likely to seriously harm the internal workings of the mechanism.
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