Tektronix 434, Instruction Manual

Page: 77 / 222

Ma i nten ance—434
4. T o replace the b o a rd , reverse th e o rder o f rem oval.
C o rre c t lo c a tio n o f th e pin co n n e cto rs is show n in Figs. 8-1
th ro u g h 8-23. Replace th e pin co nnectors c a re fu lly so th e y
mate c o rre c tly w ith the pins. I f fo rce d in to place in c o r­
re c tly p o s itio n e d , the p in co n n e cto rs m ay be damaged.
T ra n s is to r R eplacem ent. T ransistors should n o t be
replaced unless a c tu a lly d e fe ctive . If rem oved fro m th e ir
sockets d u rin g ro u tin e m aintenance, re tu rn them to th e ir
o rig in a l sockets. Unnecessary replacem ent o f transistors
m ay a ffe c t the c a lib ra tio n o f th is in s tru m e n t. W hen tra n ­
sistors are replaced, check th e o p e ra tio n o f th a t p a rt o f the
in s tru m e n t w h ic h m ay be affected.
POW ER s w itc h m u s t be tu rn e d o f f b e fo re re m o vin g
o r re p la cin g transistors.
R eplacem ent transistors should be o f the o rig in a l ty p e or
a d ire c t re placem ent. Fig. 4-4 shows th e lead c o n fig u ra tio n
o f the transistors used in th is in s tru m e n t. Some plastic case
transistors have lead c o n fig u ra tio n s w h ic h do n o t agree w ith
those shown here. I f a tra n sisto r is replaced b y a tra n s is to r
made by a d iffe r e n t m a n u fa c tu re r than the o rig in a l, check
the m a n u fa c tu re r's basing diagram fo r c o rre c t basing. A ll
tra n sisto r sockets in th is in s tru m e n t are w ired fo r the basing
used fo r metal-case tra n sisto rs. Transistors w h ic h have heat
rad ia to rs or are m o u n te d on the chassis use silicone grease
to increase heat tra n sfe r. Replace th e silicone grease w hen
replacing these transistors.
W A R N I N G
H a n d le s ilic o n e grease w ith care. A v o id g e ttin g s ili­
cone grease in the eyes. Wash hands th o ro u g h ly a fte r
use.
C a th o d e -R a y T u b e Replacement.
Use care w hen
h andling a C R T . P ro te ctive c lo th in g and safety glasses
should be w o rn . A v o id s trik in g it on any o b je c t w h ic h
m ig h t cause it to crack o r im p lo d e . W hen s to rin g a C R T ,
place it face d o w n on a sm o o th surface w ith a p ro te c tiv e
cover o r s o ft m a t under the faceplate to p ro te c t it fro m
scratches.
The C R T shield shpuld also be handled c a re fu lly . T h is
shield p ro te cts th e C R T d is p la y fro m d is to rtio n due to
m agnetic in te rfe re n ce . I f th e shield is drop p e d o r s tru c k
sh a rp ly, it m ay lose its shielding a b ility .
The fo llo w in g p rocedure o u tlin e s th e rem oval and
replacem ent o f th e cathode-ray tu b e :
A . R E M O V A L :
1. R e m o v e the w ra p -a ro u n d c a b in et as described
p re vio u sly.
2. Remove the lig h t filte r .
3. Remove the cover pla te fro m th e rear casting.
4. Remove the socket fro m the base o f th e C R T.
5. Remove the 2 A x is C irc u it Board fro m the in s tru ­
m ent.
6. D isco n n e ct th e d e fle c tio n plate leads fro m th e neck
o f th e C R T . Be ca re fu l n o t to bend or excessively squeeze
th e pins.
7. Remove the tw o screws securing th e rear o f th e CRT
shield to the rear casting.
8. Remove the d e la y-lin e assembly fro m the C R T shield
by re m o vin g th e lone screw in th e m id d le o f the delay line.
9. Remove the tw o screws securing th e C R T shield to
th e f r o n t casting.
10. Remove th e C R T assembly fro m the in s tru m e n t.
11. Loosen th e C R T clam p at th e rear o f the CRT
shield.
12. H old one hand on th e C RT faceplate and push
fo rw a rd on th e C R T base w ith the o th e r. As the C R T starts
o u t o f th e shield, grasp i t fir m ly . When th e C R T is free o f
th e c la m p , slide th e shield c o m p le te ly o f f the C R T.
B. R E P L A C E M E N T :
1. Loosen the fo u r hex-head screws on the f r o n t p a rt o f
th e C R T shield.
2. Insert th e C R T in to the shield. Loosen the tw o
securing screws inside the rear o f the C R T shield. Be sure
th e faceplate o f the C R T is flu sh o r s lig h tly recessed w ith
th e fr o n t opening o f th e C R T shield. D o n o t tig h te n the
C R T cla m p y e t.
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