Tektronix 1L40, Instruction Manual

Page: 43 / 145

Maintenance— Type 1L40
To Phase Lock
(Low loss cable w ith
clear plastic outside coating)
grn on w ht pin clip wire
CATHODE END TRIMMER SCREW
blu-red on w ht
pin clip w ire
FILAMENT PINS
b lk-b rn on w ht
pin clip w ire
To M ixe r
(Lossy coa xia l cable w ith
w hite outside coating)
1 1 9 -0 1 0 7 -0 0 PROBE
Etched Circuit Board
blu on w ht pin clip wire
Fig. 4 -3 . Assembly align m en t diag ram .
TABLE 4-2
W irin g -C o lo r Code
S upply
Back­
ground
C olor
P o la rity
1st
Stripe
2nd
Stripe
3rd
Stripe
( I f a p p li­
ca b le )
- 1 0 V
Tan Brown Black
+ 1 0 V ^
W hite Brown Black
+ 7 5 V W hite Violet Green Black
+ 100 V W hite Brown Black Brown
— 150 V
Tan Brown Green Brown
+ 2 2 5 V White Red Red Brown
RF cables in the RF and IF sections are miniature coaxial
cables. Some of these cables have a lossy characteristic and
are identified with a white outside coating. The standard
50 ohm low-loss coaxial cables have a clear plastic outside
coating. Do not interchange the lossy type with the standard
50 n type when these coaxial cables are replaced.
Removing and Replacing Assemblies or Sub
Assemblies
W A R N IN G
Disconnect the instrum ent from the p o w e r source
before a tte m p tin g re p a ir a n d /o r replacem ent o f
any assembly or sub assembly.
Oscillator Assembly
The oscillator assembly should not be removed or replaced
until tests indicate the oscillator failure is due to a faulty
tube or varactor. Before removing the assembly, check the
supply voltages and the filament circuit for continuity. The
B-f- voltage is + 1 5 0 V, the filament supply is + 1 0 V and
the voltage to the variable capacitance diode should measure
between + 1 .5 V to + 1 4 V.
1. Disconnect the four push-on clip wires and the two
push-on coaxial cables, see Fig. 4-3.
2. Remove the upper right-hand spacer rod from the plug­
in.
3. Loosen the lower set screw on the rear-panel oscillator
bracket.
4. Remove the tuning knob and retaining nut which holds
the dial mechanism to the front-panel.
5. Pull the rear of the oscillator assembly up and to the
right to remove. The locating pin on the front of the oscil­
lator assembly may bind slightly.
To replace the asssembly, reverse the removal procedure.
The retaining nut should be installed and tightened before
the set screw on the rear-panel oscillator bracket is tightened.
The second set screw on the top of the oscillator bracket
provides assembly alignment to the front-panel.
6. Recalibrate as directed in the Calibration procedure.
4 -3