TM
11-5835-243-34/EE641-AA-MMI-010/E154
MTT/TO
31S3-4-110-1
Table 3-2. Tape Transport Troubleshooting ChartContinued
Trouble
Probable cause
Action
Instantaneous speed variation excessive
Motor/tach dirty.
Check tack ripple voltage (table 3-3)
(ISV not within tolerance).
(should be less than 200 mV). Clean
tach and/or motor commutators.
Replace motor assembly.
Power cycle test failed.
Ground wire loose.
Check ground points.
Tape transport current excessive.
Check power circuitry.
Short circuit.
Tape cartridge bad.
Replace cartridge.
Clean capstan.
Start/stop time excessive.
Capstan shaft dirty.
Replace cartridge.
Tape cartridge bad.
Table 3-3. Power Amplifier Operating Voltages
Speed and direction
Reference
FAST FWD
FAST REV.
FWD
Signal
Remarks
STOP
REV.
(Note 3)
+ 1.2
+1.4
A9A1B
0.5
0.6
0.6
Note 4 DRIVE A
GROUND
+1.3
+ 1.9
+1.9
Note 4 DRIVE B
0.2
0.4
A9Q7B
GROUND
4.1
+ 3.6
+5.7
A9Q5C
A9Q6C
0.0
6.3
Note 5 MOTOR DR
0.0
+ 0.9
+0.9
A9Q1E
0.0
0.0
GROUND
Note 6
+27.1
+27.0
+ 27.8
+27.5
+27.5
GROUND
A9Q2B
Note 6
+ 0.4
+0.4
A9Q3E
Note 6
0.0
0.0
0.0
GROUND
+ 0.1
+0.0
+ 1.3
+1.3
+0.7
A9Q7E
Note 6
GROUND
+ 0.6
+0.6
+ 5.2
+7.3
+0.6
A9Q6C
GROUND
Note 6
0.0
+0.6
GROUND
0.0
Note 6
+ 0.6
+0.1
A9Q5E
+6.2
+ 4.1
+ 0.9
+1.0
+0.2
A9Q6C
GROUND
Note 6
+4.8
+ 2.5
4.7
2.4
TP5A5
Note 7 TACH DR
TP6A5
0.0
NOTES
1.
Use power amplifier schematic diagram (fig. FO-5) in conduction with this table.
2.
All readings in vdc with cartridge near BOT. These voltages are approximate and only in-
dicate general operating levels.
3.
Ground is R6, pin 1.
4.
If DRIVE A or DRIVE B signals are absent, check input circuitry.
5.
If motor drive signal (output) is incorrect, check motor winding for short to ground or open
winding. If motor is OK, refer to note 6.
6.
If input signals are present but motor drive signals are incorrect, use these signal levels to
isolate the fault y piece part(s). Repair by replacing faulty component(s). If necessary, com-
ponents may be removed from card in order to test.
7.
Tach drive voltage is shown for reference only.
CAUTION
d. When BOT is reported, turn off TRANSPORT
When replacing power transistor, apply
power and reinstall cards A1, A2 and A3.
heat sync compound (Dow Corning #340
e. Set WRITE switch on exerciser off. Depress
Silicone) to the base of component.
RUN FORWARD. Observe that the signal present
at TP1, 2 and 3 of A1, A2 and A3 is broadband noise
3-21. Erase Verification
at an amplitude of approximately 0.5v peak-to-peak.
a. Turn off TRANSPORT power on exerciser and
3-22. Magnetic Tape Cartridge Troubleshooting
remove digital read/write circuit cards A 1, A2 and
A3.
When a magnetic tape cartridge fails any of the
b. Turn on TRANSPORT power.
functional troubleshooting tests in paragraph 3-19,
c. Depress WRITE (on) and RUN FORWARD
locate failure in "Trouble" column of table 3-4 and
take the specified action. When a repair has been
switches on exerciser. Mow tape transport to run
for one minute. Depress STOP then REWIND
completed, perform entire test to verify the repair.
switch on exerciser.
3-14
