Panasonic Ju4755 Service Manual

							r 
/ 
r / 
1/ 
1 
r  
\, 
Fig. 9.2 
-
1-. / I 
1 / -
A  B  
/ i J 
V  -
V  L-V 
-
Radial Alignment  Waveforms (CATS EYE) 
A> B 
B>A 
_l -A _ A -S 
)( 100 
II lOa 
Nota: Sides 0 and 1 a,.. adjusted to agree at the actofY. If they disagree, adju them to meet the specifintions of Table 8.1 
• DAD (Dynamic Alignment Diskette) 3.5-inch 
(4) Watch  the output waveforms for sides 0 and 1.  The y should  appear as shown in Fig.  9.3. 
(S) Measure the timing level s Al to A4 and  81 to 84 in Fig.  9.3,  and calculate the lobe ratio  from  the following 
formulas. EB }:A x100% 
EA ~ A
						

							9.6 Azimuth Verification 
(1 ) Insert an alignment diskette.  Seek  to the  trac k specifie d in the azimu th column of Table B.l . 
(2)  Set the 
oscillosco pe in the same  conditions as in B.3,  and set  horizontal deflection to 0 ,5 ms /division. 
(3)  Meas u
re as shown below . 
(4)  Confirm that the measured value meets the specificat ion s in the azimuth  column  of Table  B.l, 
B c 
B C c o A B 
A 0 
A 
:! 
A)!,m u(h  0  wave form$ 
CaseofB> C C_ofB( (AI C- B Azimurh ,. ---x (AI C- A 
9.7 Index Burst  Verificat ion 
3 .5·inch IAI : CE -30 
DAD -15 
Fig.  9.4  Azimuth  Waveform , 
S.2S·inch 1M: 12 
(1) I nsert an alignment diskette. Seek  to th e  track  spec if ied  in  the li B  column of Table B.l . 
(2)  Set the 
oscillosco pe time base as follows: 
S.2S
·inch: 50 ps /divisio n 
3.5-inch :  1 m s/d ivisio n 
(3)  Check 
that the time from oscillosco pe sta rt to  the  first  data pulse mee ts the 1/ 8 speci fications  o f Tabl e 8.1. (DAD 
system) 
(4) 
It the speci fications  are not met,  adjus t as follows. (No adjustme nt  necessary  fo r 3.5 ·i nc h models) 
• 
Loosen the i ndex  detector m ounti ng  screws  enough to free the asse mbly . 
• Adjust the timin g to 200 ± 200 psec. 
• 
Reti g hten the screw . 
• Check the timing  again. 
I I ndell. Burst .. / 
v 
Fig . 9.5 Index Timing 
- 10  - 
						

							• • 
• 
• 
• 
9 .8  Track 00 Sen sor  Adjustment 
(1 ) Set the oscilloscope as follows. 
Set horizontal deflection  to  1 mYdivision . 
CH1 EX T 
S.2S-i nch TP-8 Tp·12 
3.5·in ch zp SP 
(21 Step between specified  tracks at in the FLAG 0 item ofTable 8.1 (Turn the seek delay  switch on the exer ciser to adjust  12 
ms seek.) 
(3) loosen  the track 0 sensor  screw and adjust until the waveform  on the oscilloscope appears  as shown  in Fig.  9 .6 . 
A 
--+----sv 
'---------~------GND 
ADJUST A :B TO 1: 1 
Fig. 9 .6  Track 0 Waveform 
g,g limiter V eri fication (S;)S:inchr 
(a.) 
(b) 
Seek to track 00. 
Push the carr iage outwllrd until it contacts the limiter, and recOlIlibrate . 
Make sure that the carriage  moves inward and returns to track  00. 
{el If the  carriage  does not return to track 00 in Step (b), or if it contacts the limiter  of the stepper motor. the stepper motor 
assembly must  be replated  because  adjustment is u§eless. 
9.10 limiter Adjustment  (3.5-inchl 
(11 Seek to t rack O . 
(21 Write  2F data on track 0, and measure  read level. 
(31 Loosen the limi ter mounting screw to free the limiter. 
1 4 1 
M ove the limi ter  until it just touches the head  carriage on -1 track . and retighten the limiter mounting screw 
sec urely. 
(5) Check that,  when  the A E CAL switch on the exerciser is pushed ON, the head  return s to track 0 and that the 2F 
output level is the same as that measured  in Step (21. 
9.11  Asymmetry  Verification 
(1 ) I nsert  a work  diskette. 
(2) 
Step to the  track  specifie d in the sym metry item of Table 8.1 . 
(3) 
Set the oscilloscope as follows: 
CH1  CH2 
S
.2S-inc h TP-6 .. II TP/ 
3.5·inch RD T1 
-11 - 
						

							(4) Write If. 
(5) A read walle form is displayed on the oscilloscope as shown  in Fig . 9.7. 
(6) Confirm  if it  1atisfies the villue as shown in Fig . 8.1. 
-
						

							• • 
• 
PART .11 
11.  REMOVALS  AND INSTALLATIONS 
11.1 P C B Removal and Installation (See Fig. 11.1) 
(1)  Remove the two printed circuit board 
mounting screws . 
(2)  Disconnect the connectors (J3 CON, J4 CON, 
J6 CON,)5  CON,J8CON) from the printed 
circuit board. 
(3)  Remove the printed circuit  board by sliding it 
aslant. 
(4) To reinstall , reverse the above  procedure . 
(5) Readjustment is not  necessary after printed 
circuit board replacement . 
Printed Circuit Board 
8 
Fig_ 11.1  Pri nted Circuit Boa rd  Remo val 
11 .1 - 
J6CON 
Note: :::elese connect ion prevention pin is not p rovided in 13 and J6. ,,-e::  install ing the P  .e.e . board, connect them so that the white ·c or. !n e B (onnector is facing upwards  and J6 connector pin ,: . - .a:t.,es the p.e. B. side pin No. 
-13 -
11.2  Front  plate  Removal and Installat ion 
(See Fig.1 1.2) 
(1 ) Operate the  lock  cam  of the clamp  assembly, 
and 
turn the damp handl e in the direction  of 
clamping . 
(2) Remove the clamp handle . 
(3) Remove the two front plate mounting  screws, 
and 
take o ff the front  plate. 
(4) Reverse the  above  procedure to rein stall. 
Clamp 
Lock Cam (Clamp  Assvl 
Fig.11.2 Front Plate Removal 
11.3  Track 00 Assemb ly  Re m ova l and Insta llatio n 
(See Fig.11.3) 
(1) Remo ve  the  track 00 assembly  mounting 
screw and take out the track 00 assembly. 
(2) Pull out the whit e, yellOW, and green wires 
f rom 
J6CON (lOP) . 
(3) Reverse the above  procedure to reinsta ll. 
(4) After reinstal lation,  adjust the track 00 sensor 
as 
describ ed  in 9.B . 
Trac::k....o Assemb lv 
J6CON 
Fig.11.3 Track 00 Assembly Removal  
						

							11.4 Collet Assembly Removal, Inst allation. and 
Adjustment  (See Fig.11.4) 
(1) Remove the Cartridge  Guide Assembly  as 
desc
ribed in 11. 7 
(2) Remove the lifter  spring  from the lifter. 
(3) Remove the E-ring  from the lifter shaft. 
(4) Remove the lifter from the Cartridge  Guide. 
(5) Remove the Collet Assembly  from the Guide 
shaft. 
(6) Reverse the above proced ure to reinstall. 
(7) After  reinstallation,  perform collet assembly 
center adjustment. 
(B) Collet assembly center adjustment. 
a) Temporaril y fasten the Cartridge  Guide 
Assembly . 
b) Insert a diskette  or dummy  diskette and 
damp it. 
c) Clamp repeatedly  a few  times to find  a 
good  fit 
between the collet  and the 
inside diameter of the DO motor. 
d)  Bind 
the screw ofthe Cartr idge Guide . 
e) Check step c) again, if not good repeat 
steps a) through d) unti l the correct 
center adjustment is achieved. 
Col!et A~sembly _____ • 
~ 
• 
Fig.  , 1.4 Collet Assembly  Removal  , 
1.5 
Clamp Assembly  Removal and Installation 
-14  -
(1) Remove the front plate as descr ibed in 11.2 . 
(2) Remove the two damp assembly  mounting 
screws. 
(3) Remove the damp assemb ly . 
(4) Reverse the above  procedure to reinstall. 
@ 
Fig. 1.5 Clamp Assembly Removal 
•  
						

							• • 
• 
11.6 Write Protect Sensor/Index Detector  Assembly 
Removal 
and Installation  (See Fig. 11.6) 
(1) Remove the front plate as described in 11.2. 
(2) Remove the write protect senso r mou nting  g 
screw 
and index detector mounting  screw 
respectively. 
(3) Remove the wr ite protect sensor/index 
detector assembly. 
(4) Reverse the above  procedure to reinsta ll. 
(5) When reinstalling the write protect sensor, 
exercise 
care so that the leads  and write 
protect sensor will not project  from the 
bottom and side  of the base. 
(6) After  index detector installation,  adjust the 
index timing  as described in 9.7 . 
@ 
Fig.11.6 Write Protect Senso r/ Index Detector 
Assemb ly  Removal 
11.7  Cartridge  Guide Assemb ly  Removal  and 
Installation  (See 
Fig. 11.7) 
-15 -
(1) Remove the printed  circuit board as described 
in 
11.1. 
(2) Remove the front  plate as described in 1 1.2. 
(3) Remove the shield plate mounting  screw and 
take the shield  plate off. 
(4) Remove the write protect  sensor as described 
in 11.6. It is not nece ssary to remove the 
index detector. 
(5) Remo ve the four cartridge  guide mounting 
screws  and 
take out the cartridge  guide 
assembly. 
(6) After  reinstallation,  adjust the collet assemb ly 
as 
in 11. 4 step (6) and  adjust the index  timing 
as 
in 9.7 . 
(7) When remo ving or reinstalling , be careful not 
to damage the carriage  arm with the lifter . 
Insulat ing Paper 
Shi,dPlot, ~ 
~,t--' 
Cartridge Guide 
Assembly 
~ 
						

							11.8 Stepper Motor Assembly  Removal and 
Installation (See Fig. 11.8) 
(1) Remove the insulating paper and shiel d 
plate. 
(2) Remove the track 00 sensor as described in 
11.3 . 
(3) Remove the two (M2 x 4) actuator screws that 
fasten the actuator to the carriage  arm 
assembly . 
(4)  Remove 
the two (M3 x 6) stepper motor 
asse mbly mounting  screws and then the 
stepper·motor. 
(5) Reverse the above procedure  to r einstall. 
(6) After  reinstalla tion , perform  limiter chec k as 
i n 
9 .10 and  radial alignment adjustment as in 
9 .5 . 
(7) Adjust the  track 00 senso r accordin g to the 
instruction  in 9.8 . 
Fii- .8 Stepper Motor  Assembly  Removal 
-16 -
11.9 Carr iage Arm  Assembly  Removal and 
Installation (Se e Fig.11 .9) 
(1) Remove the printed circuit  board  as described 
in 11.1 . 
(2) Remove the insulating paper and shield  plate. 
(3) Remo ve the track 00 assemb ly  as  descr jbed in 
11.3. 
(4) Remove the stepper motor assemb ly as 
descr ibed in 11.8 . 
(5) Remove the two guide  rod clamp mounting 
screws. 
(6) 
Remove the carriage  arm assembly, guide 
rod 
damp, a nd guide rod . 
(7) Pullout the guide  rod from the carriage arm 
assemb
ly. 
(8)  Reverse 
the above proce dure to reinstall. 
(9) After replacement, perform  limiter 
adjustment as described in 9.10, track 00 
sensor adjustment as  described  in 9.8 , a nd 
r a dia l al i
gnment adj ustment as desc ribed  in 
9 .5 . 
Gu ~eR.'~C-_____ . __ ~' 
Fig. .9 Carriage Arm Anembly Removal  
						

							• 
• 
• 
• 
• 
1.10 Drive  Motor  Removal and Installation 
(See Fig.11.10) 
(1) Remove the printed circuit board as 
described in 11.1. 
(2)  Remove the insulating paper and shield 
plate. 
(3) Remove the front plate as  described in 11.2 . 
(4)  Remove the write protect senso r as describ ed 
in 11.6. 
(5)  Remove the cartridge guide assembly as 
described in 11.7. 
(6)  Remo ve 
the three drive motor mounting 
screws and take off the drive motor from the 
base . 
(7)  Disconnect the drive motor connector pins 
from  the connector. 
(8) 
Rev erse the above procedure to re install . 
(9) When reinstalling, make sure that the drive 
motor connector is connected  in the correct 
direction . 
(lO)After 
reinstallation. perform motor speed 
adjustment as  described in 9. and also the 
adjustments  necessary upon reinstallation of 
the cartridge guide as des cribed in 11.7 . 
Drive  Motor 
Fig. 11.10 Drive  Motor RlHTloMi 
-17-
11. LED Assembly Removal and Installation 
(1) Remove the clamp  handle and front plate. 
(2) Disconnect the connectors J8 CON from the 
printed circuit board . 
(3) Remove the lED Assembly by  sliding it aslant 
from the Cartridge  Guide Assembly. 
(4) Reverse the above procedure to reinstall. 
LED Assembly • 
Fig.11. LED Assembly  Removal  
						

							12. TEST POINTS 
Printed  Circuit Board 
(Top view) 
GND lNTTRK00 
Vout(-) Vout(+) + READ DATA 
STEP 
-18  -