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Maintenance— Type 1L40

‘P’ W h t-v io -b lk

'O ' W h t-b lu -b lk

‘ N ’ W H f-grn-blk

•M’ W h t-o rn -b lk

W ht-vio

‘K ’ W h t-b lu

‘J’ W ht-g rn

W ht-o rn

‘H’ W ht-red

*G’ W h t-b lk

•F' W h t-b rn -b lk

'E' T a n -b rn-b lk

‘ D* (no connection)

*C* (no connection)

*B’ C oaxial

‘A ’ Shield

Fig. 4 -6 . W ire and cable color code to the honeycomb pin connectors.

2. Remove the two screws securing the DISPERSION

RANGE switch mounting hardware to the rear plate and

swing the switch assembly out of the way behind the rear

plate.

3. Remove the fourteen Phillips head screws fastening the

IF chassis to the base assembly (top plate).

4. Swing the chassis up and out, to rest on the instruments

spacer  bars  (see  Fig.  4-5).  It  may  be  necessary  to  disconnect
the  coaxial  cable  from  J147.  Do  not  use  force,  as  some  of
the  parts  are  critically  positioned  and  should  not  be  moved
out  of  adjustment.

5. Insure that none of the terminals and tie points are

shorted  or  grounded.  Reconnect  any  cables  or  wires  that
may  be  disconnected.  Fig.  4-6  illustrates  wiring  color  code.
A pply  power  if desired.  The  ground-wire  on  the  DISPERSION

RANGE  switch  must  be  grounded  for  proper  operation  of
the  instrument.  Fig.  4-2  illustrates  the  component  layout
and  circuit  layout  on  the  honeycomb  chassis.

6. Remount the chassis using the reverse procedure of

steps  1  through  5.  Do  not  force  the  chassis  into  place.  Check
for  pinched  or  undue  strain  on  the  wires  and  connectors.
When  replacing  the  DISPERSION  RANGE  switch,  make
certain  its  shaft  is  properly  coupled  to  SW365.  Check  the
operation  of  the  DISPERSION  RANGE  switch  and  insure  that
the  knob  is  properly  indexed  with  the  front  panel  markings.

Removing the Phase Lock Assembly

1. Switch the power to OFF and remove the instrument

from the plug-in oscilloscope.

2. Unplug the signal lead (J885) from the phase-lock

assembly.

3. Loosen the set screw for the FINE RF CENTER FREQ

control and remove the knob.

4. Use a

5/u

inch nut driver to remove the mounting nuts

securing the front panel phase-lock controls (FINE RF FREQ,

LOCK  CHECK  and  INT  FREQ  control).  Keep  the  nut  for  the
INT  REF  FREQ  control  separate  from  the  others,  because  it
has  a  different  thread  and  w ill  bind  if  it  is  placed  on  the
wrong  control.

CAUTION

Do  not  loosen  o r  move  the  pickup  p robe  in  the
o s c illa to r  assembly.  Its  position  is  c ritica l  fo r  proper
o p e ra tio n   o f  the  o scilla to r.

5. Remove the six Phillip head screws located along the

edge of the "U " shaped phase-lock assembly cover.

6. Slide the assembly back and out of the "U " shaped

cover. Be careful that the mounting screws fo r the low pass

filter do not catch the chassis.

7. Support the phase-lock assembly on a small block (see

Fig.  4-7),  then  connect  the  signal  lead  from  the  oscillator  to
J855.  Check  the  lead  dress  and  all  connectors  to  insure  that
no  short  circuit  exists  and  all  connections  are  correct  (see

Fig. 4-8). Power can now be applied and the phase-lock circuit

checked for correct voltages and waveforms. Fig. 4-11 il
lustrates component layout on the circuit board.

Fig. 4 -7 . Phase lock assembly removed and ready to troubleshoot.

8. If the circuit board is to be replaced, proceed as follows:

a. Disconnect all the signal and voltage leads to the

assembly. Disconnect the Sealectro connector to the phase
detector at the board.

b. Remove the mounting nuts for the three controls.

Push the FINE RF CENTER FREQ potentiometer and the
LOCK CHECK switch into the box. Unsolder the lead to the

BNC connector. Remove the circuit board mounting screws

and the mounting screws to the square pin connector.

c. Slip the circuit board out of the box. Repair or

replace.