Tektronix 491 Product Modification

product

modification

050

-

0692

:

()2

(' )

M21303

,

M22940

BAND

11

C

11

OSCILLATOR

REPLACEMENT

For

TEKTRONIX®

Type

491

Spectrum Analyzers

Serial

Numbers

B010000-B272355

I l O

11

Solid

State

Band

11

C

11

Oscillator

Assembly

119-0108-01

replaces

vacuum

tube

oscillator

119-0108-00

which

is

no

longer

available.

Use

of

the

new

solid

state

oscillator

necessitates

the following changes:

1)

The

dial tape

is

replaced

to

assure

oscillator

tracking

on

all

bands.

2)

A -20 Volt

Power

Supply

is

added

for

use with

the

new

oscillator.

3)

Di

al

coupling

and

osci

11

a

tor

mounting brackets

and

hardware are replaced to

accommodate

the

changed dimension

of

the

new

oscillator

assembly.

©

1974

, Tekt

ronix,

Inc.

All

Rights Reserved.

7-23-75

Supersedes

050-0692-01

TEKTRONIX

,

SCOPE-MOBILE

and

~

are

registered trademarks

of

T

ektron

i

x,

Inc.

"-

4

"'?

9

3

1~1

Type

Page

1

of

9

PARTS

INCLUDED

IN

PARTS

REPLACEMENT

KIT:

Quantity

Part

Number

Description

( 1 ea)

1

ea

l ea

ea

4 ea

l ea

1 ea

( l ea)

1 ea

l ea

ea

l ea

2 ea

l ea

l

ea

2 ea

1 ea

l

ea

l

ea

1

ea

1

ea

1

ea

*NOTE:

119-0108-01

1 75-1529-00

175-1530-00

211-0008-00

407-1545-00

407-1546-00

670-0523-08

175-1531-00

175-0998-00

175-0999-00

210-0203-00

211-0021-00

211-0098-00

331-0376-00

361-0525-00

376-0029-00

376-0099-00

384-1265-00

386-1135-01

670-3500-01

670-4193-01

Assembly

Oscillator*

consisting

of:

Osci1lator

9

RF

Cable,

50~

coax, 175-0323-00, 9 inches

w/131-0375-00

and

w/131-0977-00

Cable,

50~

coax, 175-0323-00, 6 inches

w/131-0375-00

and

w/131-0977-00

Screw, 4-40

X .250

Barcket, angle,

oscillator

front

Bracket, angle,

oscillator

rear

Wire,

#22

stranded 175-0527-00 4 inch white

Wire,

#22

stranded 175-0527-00 3 inches white-black

Assembly,

Oscillator

Connector

Circuit

Board,

consisting

of:

Circuit

Board,

Oscillator

Connector

Wire,

ribbon

w/3

wires

#26

stranded

w/3

131-0707-00

connectors

and

w/l 352-0161-00 holder

on

one

end

only.

White-brown

and

White-red

15

inches long soldered

to

circuit

board

and

White-orange 7 inches long

from

holder end.

Wire,

#22

stranded 175-0527-00 4 inch White-red

Wire,

#22

stranded 2 3/4 inches Wht-blk-yel

w/2

131-0371-00 connectors

Wire,

#22

stranded 2 inches

Wh

t-brn

w/l

131-0707-00 connector

Lug,

so 1

de

r S

E-6

long

Screw, 4-40 1.250

Screw,

button

head

4-40 x .375

Tape, Frequency

Di

al

Spacer, Delrin®

.781

inches long x .25

OD

Coupling

shaft,

rigid

.312

OD

x .5

lg

x .128

ID

Coupling

shaft,

flex

.437 long x .250

Shaft

extension,

.450 long x .125

OD

Plate,

Oscillator

mounting

Circuit

Board, -20 Volt

Power

Supply

Circuit

Board, Connector

The

front

and

rear

angle brackets are fastened to the

Band

11

C

11

Osci1lator

for

purposes

of

identification

and

orientation.

They

must

be

removed

before the

oscillator

can

be

insta1led.

Save

hardware.

® Delrin

is

a

registered

trademark

of

E.

I.

Dupont

de

Nemours

Inc.

Page

2 of 9 050-0692-02

INSTRUCTIONS:

DISCONNECT

THE

INSTRUMENT

FROM

ITS

POWER

SOURCE!

CAUTION

Removing

or

reinstalling

the instrument dust cover

may

be

hazardous

when

the

instrument

is

slid

in or out

of

the dust cover.

Remove

or

reinstall

the dust

cover

as

follows:

Pl

ace

the accessory cover

on

the instrument. Stand the instrument

vertically

on

the

front

cover.

Remove

the four

plastic

feet

and

the

two

thumbscrews

and

slide

the cover

off

of

the instrument.

A.

TO

REMOVE

OSCILLATOR

ASSEMBLY

( )

l.

Remove

the

Tuning

knob

and

the

Band

Selector

Switch

knob.

Remove

the screw

below

the tuning

shaft.

Disconnect the following wires

from

the pin connectors

on

the

connector block

on

the

chassis:

( ) 2. White-blue wire

from

J.

()

3. White-violet wire

from

I.

( ) 4. White-black wire

from

E.

Disconnect the wires

from

the

Oscillator

connector

Circuit

Board

that

connect to the

TIME/DIV

Switch

as

follows:

( ) 5.

White

wire. (Unsolder

shield

of

white-black

coax

from

pin connector).

( ) 6. White-black-brown wire.

( )

7.

White-brown-green-brown.

( ) 8. White-black wire. (Unsolder

center

of white-black

coax

from

Pin connector).

()

9. Disconnect

all

of

the sub-miniature

right

angle coaxial connectors

from

the

oscillator

assembly.

To

facilitate

reassembly label the

coax

cables

and

connectors.

( )

10.

Remove

the

Band

Switch bracket mounting screws

which

are

accessible

from

the bottom, (Note:

You

may

have

to

remove

the

rail

mounting bracket in

order to reach the top screw)

and

the

two

nuts

that

fasten the

driver

gear assembly

to

the

front

panel,

and

remove

the

oscillator

assembly.

Page

3

of

9 050-0692-02

B.

TO

REMOVE

THE

BAND

11

C

11

OSCILLATOR

( )

(

)

( )

1.

Unsolder

the

Band

11

C

11

oscillator

filament

leads*.

One

from

the

Band

'B'

oscillator

and

one

from the

oscillator

connector board.

2.

Unsolder band C

B+

lead

(orange wire) from connector board.

3. Loosen the

set

screws

on

the

Band

11

C

11

oscillator

.drive

flexible

coupler*.

4.

Loosen

the

collet

on

the

Band

11

A

11

oscillator

tuning

shaft.

5. Loosen the

set

screw (j) (See Fig. 2 page 9)

that

fastens

the

front

band svJitch

lever

to

the

coupling rod. @ .

6.

Remove

the

four

4-40 screws

@,;

that

fasten

the

dial

housing to the

front

oscillator

mounting

plate*

;3·,

and

remove

the

dial

housing.

7.

Remove

the

two

screws

that

fas

ten

the

back end

of

the

Band

11

C

11

osci

11

a

tor

to

the

rear

sup

port

bracket

(6--;.

,_...,

8. Observe

the

orientation

of

the

front

mounting

plate

(3J

,

and

remove

two

screws,

one

flat

head and

one

pan

head,

that

fasten

the

Band

11

C

11

oscillator

to

the

front

mounting

bracket.

9.

Remove

the

two

socket

head screws

~6)

that

fasten

the

front

mounting

Plate

to

the

Band

11

A

11

oscillator,

and

remove

the

Band

11

C

11

oscillator,

and

the

front

mounting

plate*.

C.

TO

INSTALL

NEW

BAND

11

C

11

OSCILLATOR

( )

1.

Temporari k

remove

the

two

screws

r28J

that

fas

ten the band switch

bracket

®

to

the

Band

11

B

11

osci

l'lftor

rear

support.

®

Fas

ten the

Band

11

C

11

osci

11

a

tor

rear

support

angle

bracket

@

over

the

band switch

bracket

with the hardware

just

removed.

( ) 2. Fasten the

new

front

oscillator

mountil']g

plate

m to the

Band

11

A

11

oscillator

using the hardware removed

in

Step

B..:-g:

( ) 3. Reins

tall

the

di

al housing

by

ins

tall

i

ng

the

two

top screws

that

fas

ten

the di al housing to the

new

front

oscil

1 a

tor

mounting pl

ate.

DO

NOT

TIGHTEN

COLLET

ON

BAND

A

OSCILLATOR.

( ) 4. Fasten the

Band

C

oscillator

front

angle

bracket

to

the

bottom holes

of

the

dial

housing and

replace

the bottom

left

mounting screw with

the button head screw.

~

* Discard.

Part

will

not

be

used in

new

assembly.

Page

4

of

9 050-0692- O 2

INSTRUCTIONS

: (Cont I d)

( )

(

)

5.

Slide

the

new

shaft

coupler

@

over

the

Band

A"

oscillator

dial

assembly

drive

shaft,

put

the

extension

shaft

~

into

the

shaft

coupler.

@

6.

Install

half

of

the

new

flexible

coupler

@.

on

the

shaft

extension

@ and

the

other

half

on

the

Band

"C"

oscillator

drive

shaft.

7.

Install

the

Band

"C"

oscillator*

as

follows:

*

NOTE:

Be

sure

the

os

ci

ll

a

tor

is

turned

to

the

high end

(fully

clockwise)

of

the

Band.

a)

b)

Align

the

two

halves

of

the

flexible

coupler@

and

insert

the

center

part

of

the

flexible

coupler.

Fasten

the

Band

"C"

oscillator

in

place

with

the

4-40 X .250 inch

screws

@·

( ) 8. Reconnect

the

band

switch

lever

to

the

coupling

rod @

on

the

dial

housing.

()

9. Align the

Band

"C"

Oscillator

as

follows:

a.

Temporarily

reinstall

the

Tuning

knob

on

the

main

dial

drive

shaft

and check

for

smooth

operation

of

the

Tuning knob.

b.

The

Band

"C"

Oscillator

rear

support

is

fastened

to

the

back end

of

the

Band

"B"

Osei

ll

a

tor

by

a

1

u•

shaped

bracket.

This

bracket

allows

mechanical

adjustment

in

two

directions.

c.

Side

to

Side

adjustment

is

accomplished

by

loosening

the

set

screw,

one

on

each

side,

and

tightening

the

set

screw

on

the

other

side.

D.

TO

REPLACE

DIAL

TAPE

( )

1.

Turn

the

Tuning di al**

all

the

way

to

the

high

end,

fully

clockwise.

( ) 2.

Remove

the

dial

window

mounting screws

and

remove

the

dial

window.

( ) 3. Manually run

the

dial

tape

off

of

the

right

hand

spool,

and

pull

the

tape

off

of

the

left

hand

spool.

( )

4.

Wind

the

new

dial

tape

so

the

low

end

is

on

the

outside.

Thread

the

dial

tape

onto

the

left

hand spool and wind

all

of

the

tape

on.

Then

slip

the

high end

over

the

right

hand spool and

turn

until

the

high end

of

the

dial

is

in

the

center

of

the

window, and

reinstall

the

di a 1 w i n

dow.

**The

collet

on

the

Band

"A"

Oscillator

and the

set

screws

in

the

Band

"C"

Oscillator

shaft

coupler

should

both

be

loose.

Page 5

of

9

050-0692- 0 2

-------------------~---------

-----------

INSTRUCTIONS:

(Cont

1

d)

E.

TO

REPLACE

CONNECTOR

CIRCUIT

BOARD

( )

l.

Unsolder

all

of

the wires

from

the

connector

circuit

board

on

the

Phase

lock chassis

and

replace the connector

circuit

board with the

new

Connector

circuit

board,

from

the

kit,

and

wire

as

follows:

--

Wire

Color

Wire

Color

----·

A

white

and

#22

bare

E*

white-black

wire to pin B

F white-brown-red

B

Shield for pins G

white-brown-green

C & D

H

white-black-brown

c

Red

I*

white-vi o 1

et

D

Black

J*

white-blue

F.

TO

REPLACE

OSCILLATOR

CONNECTOR

BOARD.

SEE

FIG.

1

( )

1.

Unsolder

all

of

the wires

from

the

oscillator

connector

circuit

board.

( )

2.

Remove

the

oscillator

circuit

board

mounting

screws

and

replace the

circuit

board with the

new

board

and

wire

as

follows:

( ) 3.

Solder the White-red wire

(See

Ftg. 1) to the

-20VDC

termina1

on

the

Band

11

C

11

osci1

lator.

( ) 4. Solder the white wire

from

the

ground

connection

on

the

Band

11

C

11

oscillator

to the

grounded**

side

of

the

Band

11

B

11

filament.

( ) 5.

Solder the white-black wire

from

the

AFC

terminal

on

the

Band

1

C

1

oscillator

to the

AFC

terminal

on

the

Band

1

B

1

oscillator.

( )

6.

Connect

the remaining wires

as

shown

in the drawing.

FIGURE

1.

WHT-BLK--

*

The

white-black,

white-violet,

and

white-blue wires will

be

connected in

step G 4-6.

**

Terminal

toward

the back.

CHECK

WITH

OHMETER

TO

BE

SURE.

Page

6 of 9 050-0692-02

INSTRUCTIONS:

(Cont'd)

G.

TO

REINSTALL

OSCILLATOR

ASSEMBLY

( ) 1. Reinstall the

oscillator

assembly in the instrument using the hard-

ware

removed

in Step

A-10.

Two

6-32

screws in the

back

end

and

two

6-32

nuts in the

front.

( ) 2. Reinstall the 4-40 screw

below

the tuning

shaft

that

fastens the

dial housing to the

front

panel.

( )

3.

Reinstall the

Tuning

knob

and

the

Band

Switch Lever,

and

switch the

Band

Switch to

check

for proper

knob

position.

The

knob

position

can

be

adjusted

by

moving

the switch

lever

on

the coupling rod.

Reconnect wires to connector block

on

chassis

as

follows:

( ) 4. White-blue wire to

J.

( )

5.

White-violet wire to

I.

( )

6.

White-black wire to

E.

Connect

wires to

oscillator

connector board terminals

from

top to

bottom

as

follows:

( )

7.

White

wire (ground).

( ) 8. White-black-brown wire.

( )

9.

White-brown-green wire.

( )

10. White-black wire.

( ) 11. Reconnect the sub-miniature coaxes

removed

in Step

A-9

and

connect the

coax

from

the

LO

output

on

the

Band

11

C

11

oscillator

to

J45

on

the

IF

Multiplexer

and

connect the

Phase

Lock

connector

on

the

Band

11

C

11

osc-

illator

to Jll40

on

the

Phase

Lock

Assembly.

( ) 12.

Dress

the three wire ribbon cable

from

the

oscillator

circuit

board

back

and

through the chassis. Solder the white-orange wire to the

ground

solder

lug

on

the

power

supply chassis near

C954.

The

connector will

be

connected to the

new

-20 Volt

Power

Supply in

Step

H-8.

Page

7

of

9

050-0692-02

INSTRUCTIONS:

(Cont'd)

H.

INSTALL

THE

-20VOLT

POWER

SUPPLY

AS

FOLLOWS:

( ) 1. Place the instrument

on

the

workbench

bottom side up, release the lock

on

the

IF

Control

Circuit

Board

and

swing

it

open

to gain access to

the

Power

Supply

Circuit

Board.

{ ) 2.

Add

the

#6

solder

lug to the bottom

mounting

screw of the

RFI

filter.

Solder the white-brown wire,

from

the

kit,

to

this

solder lug. Other

end

will

be

connected in Step

H-7.

( ) 3.

Remove

the

two

mounting

screws

from

the

Power

Supply

Circuit

Board

near the

RFI

filter.

( ) 4. Disconnect the white-black-yellow wire

from

AA

on

the

Power

Supply

Circuit

Board.

Connect

the 2 3/4 inch white-black-yellow wire

from

the

kit

to

AA.

These

b-10 wires

wi

11

connect to the

new

circuit

board in Step

H-6.

( ) 5.

Mount

the -20Volt

Power

Supply Circuit

Board

above

the

Power

Supply

Circuit

Board

on

the

.781

inch spacers

and

fasten in place with the

1.250 inch

4-40

screws in the holes vacated in Step

D-1.

( )

6.

Connect

the

two

white-black-yellow wires mentioned in Step

H-4

to

A

and

B

of

the -20Volt

Power

Supply.

( )

7.

Connect

the white-brown wire

installed

in Step

H-2

to

C of the

-20Volt

Power

Supply.

( ) 8.

Connect

the

two

wire ribbon connector

from

the

oscillator

connector

board to

P920

on

the -20Volt

circuit

board.

( ) Refer to the

Calibration Procedure in your

Instruct~on

Manual

and

the supplemental Calibration procedure in the Instruction

Manual

Modificat.ion

Insert

at

the

back

of

thjs

kit

and

recalibrate

as

required.

( )

For

future reference fasten the Modification

Insert

in your Instruction

Manual.

Page

8

Of

9

050-0692-02

ITEM

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

PART

NUMBER

331-0176-03

175-1529-00

386-1139-00

119-0108-01

407-0295-00

407-0294-00

213-0075-00

260-0821-00

337-0880-00

119-0063-01

175-1530-00

407-1545-00

384-0425-00

211-0062-00

211-0012-00

210-0004-00

211-0504-00

407-1546-00

210-0006-00

211-0098-00

213-0004-00

210-0405-00

210-0053-00

131-0391-00

176-0124-00

211-0564-00

175-1531-00

211-0008-00

670-0523-08

211-0116-00

376-0029-00

376-0099-00

384

..

1265-00

QUANTITY

1

4

1

3

8

2

1

6

1

2

3

4

As

Req.

2

1

4

1

2

1

DESCRIPTION

Dial

Assembly

Tape

Cable

Assembly,

Elec

(LO)

Plate

Mounting

Oscillator

Assembly,

RF

Support,

Oscillator

Bracket, Oscillator

Screw,

4-40 x .094 Socket

Head

Switch

Lever

Shield

Rotary

Switch

Oscillator,

Cavity

Cable

Assembly,

Elec

(Lock)

Bracket,

Angle

(Oscillator Front)

Rod,

Coupling

Screw, 2-56 x .312

PH

Screw,

4-40 x .375

PH

Lockwasher,

#4

Internal

Screw,

6-32 x

250

Bracket,

Angle

(Oscillator

Rear)

Lockwasher,

#6

Internal

Screw,

4-40 x .375 Button

Head

Screw,

6-32 x .188 Socket

Head

Set

Hex

Nut,

2-56 x

.188.

Lockwasher,

#2

Split

Connector,

coax

Wire, .0508

#16

AWG

Dia,

Tinned

CU

Screw,

6-32 x .375 Socket

Head

Cable,

Assembly,

Elec.

Screw,

4-40 x .250

PH

Oscillator Connector Circuit

Board

Screw,

4-40 x .312

Assembly

washer

Coupler

Shaft

I

II

r.;:vL.o...icr

u~.

CN-,..)

~·~

FIG.

1 A

Fig. 2

050-0692-01

Page

9

of

9

INSTRUCTION

MANUAL

MODIFICATION

INSERT

BAND

11

C

11

OSCILLATOR

REPLACEMENT

Type

491

SN

B010000-B269999

Installed

in

Type

SN

Date

~~~~ ~~~~

~~~~

This modification

insert

is

provided to supplement the

Instruction

Manual

for

the

above

listed

products.

The

information given in

this

insert

supersedes

that

given

in the

Manual.

by

Tektronix,

Inc.,

Beaverton,

Oregon.

Printed in the United States of America.

All

rights

reserved. Contents of

this

insert

may

not

be

reproduced

in

any

form

without the permission of the copyright

owner.

GENERAL

INFORMATION

Solid

State

Band

"C"

Oscillator

Assembly

119-0108-01 replaced

vacuum

tube

oscillator

119-0108-00

which

is

no

longer

available.

050-0692-02

050-0701-00

Page

1

of

11

TEXT

CORRECTION

SECTION

3

CIRCUIT

DESCRIPTION

Page

3-1

Su~-Title,

RF

Section, second paragraph,

first

sentence

CHANGE

TO

READ:

Page

3-3

Heater voltage for the

oscillators

is

supplied

by

the

+10

Volt

regulated supply,

(SN

B270000-up,

Band

C

is

a

solid

state

oscillator).

Sub-Title,

Band

C,

first

sentence

CHANGE

TO

READ:

Page

3-14

Band

C:

The

oscillator

for

Band

C

is

a triode

oscillator

(solid

state

for

SN

B270000

and

up)

connected to tunable transmission

lines

which

are tuned

by

the

RF

CENTER

FREQUENCY

control.

Sub-Title,

Low

Voltage

Power

Supply, paragraph one,

line

five

Insert

the following sentence

after

the sentence ending with the word,

volts.

Page

3

-15

For

SN

B270000

and

up:

A regulated -20 volt

power

supply,

provides the

power

for the

Band

C

oscillator.

Insert

the following paragraph

after

the

-10

Volt

Supply

description.

SECTION

4

Page

4-14

SN

B270000-up:

-20 Volt Regulated Supply.

The

-20 Volt

supply consists of

an

integrated

circuit

voltage regulator

U925,

series

pass

transistor

Q926

and

a voltage doubler

comprised

of

D920, D921,

C920

and

C921.

When

the

RF

CENTER

FREQUENCY

band

selector

is

set

to

band

C,

K927

closes

and

the

-20 volts

is

connected to the

Band

C

oscillator.

MAINTENANCE

Step 2 under the Sub-Title

Oscillator

Tube

Replacerrent

CHANGE

TO

READ:

Page

4-16

2.

Band

C

oscillator

tube replacerrent (V42),

SN

B269999

and

below.

CHANGE

Fig.

4-20A

to

Read:

Page

2 of

11

Tube

subassembly

removal

procedure,

SN

B269999

and

below.

050-0692-

02

050-0701-00

(

Page

4-17

CHANGE

Fig.

4-20B

to

Read:

Page

4-18

Tube

subassembly

installation

procedure,

SN

B269999

and

below.

Sub-Title,

TROUBLESHOOTING,

paragraph

three,

line

two

CHANGE

TO

READ:

In

Section 9 of the

Manual,

Fig. 4-23 through 4-28 provide

ADD:

Page

4-28

SECTION

6

Page

6-5

Fig. 4-28.

-20

Volt

Power

Supply

Board

with

component

callouts,

SN

B270000

and

UP.

0 5 7

FL

3 3

1U0

5 0 B +

C921

3 3

0MFD

50VDC

+

658

·7

l Stf +

'"

..

CALIBRATION

c .

'11

CHAN

GE Step 2 to

Read:

Page

6-9

2.

Check

the

+10

Volt, (-20 Volt

SN

B270000

and

U

p),

and

+150

Volt Supplies.

Part

B.

under the Sub-Title, Adjust -10 Volt Supply

CHANGE

the reference to Fig.

6-5

to Fig.

6-5A.

CHANGE

To:

2.

Check

+10

Volt, (-20 Volt

SN

B270000

and

Up),

and

+150

Volt

Power

Supplies.

050-0692-02

050-0701-00

Page

3

of

11

Step 2b:

ADD

Step 2d:

Change

the reference

to

Fig. 6-5 to Fig.

6-5A.

d.

SN

B270000

and

Up.

Set the

Band

selector

to C

and

check

the

-20 Volt

Supply

at

K927

(See

Fig. 6-5B).

Must

read

between

-19.4

and

-20.6 Volts

(-20V

±3%).

Return the

band

selector

to

Band

B.

CHANGE

Fig. 6-5 to Fig.

6-5A.

ADD:

Fig. 6-5B: Fig.

6-5B.

-20

Volt

test

point,

SN

B270000

and

Up.

Page

6-11

TABLE

6-2

ADD

the following:

-20V

-19.4V to -20.6V

<

5mV

Page

6-46

CHANGE

Fig. 6-48 to read:

Local

oscillator

assembly

showing

voltage

and

signal connections,

SN

B269999

and

below.

ADD:

Fig.

6-48B.

Local

oscillator

assembly

showing

voltage

and

signal connections,

SN

B270000

and

Up.

Page

4

of

11

050-0692-

02

050-0701-00

(

Output

to

Phase

Lock

Band

A

Inductance

Adjustment

To

T

Connector

Page

6-47

CHANGE

the Fig. 6-49 to

Read:

Fig.

6-49A.

Local

oscillator

assembly

showing

drive

shaft

coupling

and

tunig adjustments,

SN

8269999

and

below.

ADD:

Fig.

6-498

Local

oscillator

assembly

showing

drive

shaft

coupling

and

shaft

coupling

and

tuning adjustments,

SN

8270000

and

Up.

050-0692-02

050-0701-00

Page

5

of

·

11

Page

6-48

Band

A

trimmer

capacitor

adjustment

Band

C

drive

shaft

Setscrews

that

lock

drive

coupler

to

band

B

drive

shaft

Band

B

capacitance

adjustment

CHANGE:

Fig. 6-50 to

Read:

Band

C

Assembly

Alignment

Diagram

SN

B269999

and

below.

Sub-Title,

BAND

C

OSCILLATOR

CALIBRATION

CHANGE

TO

READ:

BAND

C

OSCILLATOR

CALIBRATION

(SN

B269999

and

below).

Page

6-50

Insert

the following

after

the

last

paragraph

on

the page.

Page

6

of

11

TRACKING

THE

BAND

C

OSCILLATOR

TO

THE

DIAL

ASSEMBLY,

SN

B270000

and

Up.

NOTE

This

procedure should only

be

required

after

the

Band

C

oscillator

has

been

replaced.

The

oscillator

assembly

must

be

removed

from

the instrument.

See

Maintenance Section.

050-0692-02

050-0701-00

(

FINAL

CHECK

Calibration

of

this

oscillator

is

very

critical

and

should

only

be

attempted

by

qualified

personnel with adequate

facilitaties.

The

complete

oscillator

assembly

is

listed

in the

Mechanical

Parts

List.

We

recommend

exchanging the

complete assembly under the Tektronix exchange

program.

Contact your local Tektronix Field Office

or

representative

for exchange

rates.

a.

Tune

the

oscillator

to

4.2GHz.

Set dial assembly to

4.0GHz

and

lock the dial assembly to the

oscillator

tuning

shaft.

b.

Check

oscillator

tracking through the frequency range.

Must

track

within±

(1%

of

the indicated dial reading

+200MHz).

It

may

be

necessary to introduce

some

error

at

the upper or

lower frequency

limits

to bring the tracking within the

±1%

specification.

c.

Check

the

phase

lock operation over the frequency range.

Check

for the presence

of

beat frequency signals

and

stable

locking operation.

d.

Tune

to the

low

end

insuring the

oscillator

assembly

is

operating

and

no

internal stops are encountered.

a.

Install

the

oscillator

assembly into the

unit.

b.

Check

the

oscillator

tracking over the frequency range, the

proper operation

of

the phase lock

circuit,

and

analyzer

sensitivity.

Page

7

of

11

050-0692-02

050-0701-00

ELECTRICAL

PARTS

LIST:

Ckt.

C40

C920

C921

C926

C1176

D920

D921

K927

Q926

R42

R43

R47

R920

R921

R922

R923

R926

R927

U925

V42

No.

Part

Number

290-0409-00

290..;0325-00

290-0325-00

281-0523-00

285-1123-00

152-0061-00

108-0405-00

151-0364-00

DELETE

321-0311-00

321-0247-00

315-0302-00

315-0202-00

308-0565-00

156-0071-00

DELETE

Description

CAPACITORS

lOOOµF

25V

330µF

50V

330µF

50V

lOOpF

350V

lµF

200V

DIODES

Silicon

200V

5µA

Silicon

200V

5µA

RELAYS

Cai

1 ,

Fixed

reed

drive,

12

V

TRANSISTORS

Silicon,

NPN

RESISTORS

16.

9k

3.65k

3k

2k

15k

1/8W

1%

l/8W

1%

l/4W

5%

l/4W

5%

l/4W

5%

4W

1%

INTEGRATED

CIRCUITS

Voltage regulator

VACUUM

TUBES

MECHANICAL

PARTS

LIST

CHANGES

ADD:

CHANGE

TO:

Fig. 5-28

Fig. 5-31

670-3500-01

670-4193-01

119-0106-03

670-0523-08

*

179-1099-02

119-0108-01

Circuit

board, -20 Volt

Power

Supply

Circuit

board, Connector

1

OSCILLATOR

ASSEMBLY

ASSEMBLY,

Circuit

Board

OSCILLATOR

CONNECTOR

CABLE

HARNESS

OSCILLATOR

ASSEMBLY

RF

BAND

C

331-0176-03**

1 Fig. 5-33

DIAL

ASSEMBLY,

Tape

*

Opt.

2 instruments

use

670-0523-07.

**

Opt.

2 instruments

use

331-0176-04.

Page

8

of

11

050-0692-02

050-0701-00

RE

51STOR'21"0N

OSC

ILLAIOR

PC

BOARD

'\

G

R4s•+

1

::b

\

rT0040:

LO

rt~~~SE

:

LOCK.

1-/f'~r-

-

-1'-r1

:

I

~

BANDC

~

1

I

OOSCILLATOR

I

~

1

,

I

1.7-4

.ZGHz.

I \

I_

- - -

__J

',,

-20V

\

-t-l~OV

C40

I000""1,F~

CCR.REC.

TIVE

-2ov

FROM~

SIG-NA~R.OM

K92.7~

Qll80~

PARTIAL-

0

RF

SECTION

'

A

MHz.

\

B

MHz.

c

TO

RI

17~

0

TO

J920,

<&

*

Not

present

on

Opt. 2 instruments.

050-0692-02

050-0701-00

Page 9

of

11

<O

''

~

PWR

SP

LY --< I A

l!.R.00

ili

FROl.A

I

C92.0

TERM

I!>

--(

~30,.F

OF

T900

<f9

8 +

r-:.----

L/1

092.0

C92.I

3'.30rF

U925

.-----"

,uA1?.'.3C

...,

Page

10

of

11

-20V

PO

U925

FREQ.

COMP

C9'Z.<o

I!

IOOpF

WER

SU

PPLY

SN

B270000-UP

050-0692-02

050-0701

-00

Q9Z"

+150V

FROM

BND

0L

SW

l

y..oJ9'Z.0

-z.ov

TO

OSC

0

·,

(

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Tektronix 491 Product Modification

Tektronix 491 Product Modification

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