Tektronix 7A26 User manual

040-0785-01

VERTICAL AMPLIFIER MICROCIRCUIT REPLACEMENT

For the following TEKTRONIX ®instruments:

7A26 Serial Numbers BOlOlOO -B139377

This kit provides parts and instructions to replace one of the

vertical amplifier microcircu«‘s. For serial numbers below

B1 10000, the emitter compensation networks for U1750 and

U2750 need to be modified. In order to optimize the lOOHz

to lOOkHz square wave response (low-frequency

compensation) .selection of several components may be

necessary.

Tektronix, Inc. Supersedes: 13-JUL-1979

TEKTRONIX, SCOPE-MOBILE and are registered trademarks of Tektronix, Inc. SONY /TEKTRONIX is aregistered trademark of Sony /Tektronix, Inc.

CAUTION

STATIC SENSITIVE DEVICES

Static discharge can damage any semiconductor component

in this instrument. Static voltages of IkV to 30kV are

common in unprotected environments.

TO AVOID DAMAGE. OBSERVE THE FOLLOWING:

1. Minimize handling of static-sensitive components.

2. Transport and store static-sensitive components or

assemblies in their original containers, on ametal

rail, or on conductive foam. Label any package that

contain^ static-sensitive assemblies or components,

3. Discharge the static voltage from your body by

wearing awrist-strap while handling these

components. Servicing static-sensitive assemblies or

components should be performed only at astatic-free

work station by qualified service personnel.

4. Nothing capable of generating or holding astatic

charge should be allowed on the work station

surface.

5. Keep the component leads shorted together whenever

possible.

6. Pick up components by the body, never by the

leads.

7. Do not slide the components over any surface.

8. Avoid handling components in areas that have afloor

or work-surface covering capable of retaining a

static-charge,

9. Use asoldering iron that is connected to earth

ground.

10.

Use only approved. anti-static type. desoldering

tools.

040-0785-01 page 2

KIT PARTS UST:

Ckt, Number Quantity Part Number

A1ea 155-0078-10

C1/21

C2721 2ea 281-0123-00

R1722

R1724

R2722 4ea 315-0150-00

R2724

1ea

*U1350, U1450, U1550. U1750. U2350

Description

Microcircuit, li. vertical amplifier

Capacitor, var. cer. 5-25pF. lOOV

Resistor, cmpsn. 15n. 5%. 0. 25W

Label. 040-kit

U2450. U2550 or U2750

Fig. 1. Partial -Amplifier circuit board (solder side)

040-0785-01 page 3

INSTRUCTIONS;

WARNING

Before proceeding, ensure the mainframe power

switch is in the off position, then remove the

amplifier plug-in from the mainframe.

()1. Remove the left and right side electrical shields.

NOTE

The emitter compensation networks for U1750

and U2750 were modified at serial number

B1 10000. Steps 2through 16 are instructions

to add this modification to the *7A26.

Therfore. these instructions (steps 2through

16) may be disregarded for amplifiers in

serial number range B1 10000 to B139377 or

in Instruments which have already had this kit

installed.

Steps 2through 8involve the removal of

Cl 721. C2721. R1721 and R2721. These

components were added to the 7A26 at serial

number B050000. Instruments in serial

number range BOlOlOO to B049999 may

disregard steps 2through 8.

()2. Remove the CHI Readout circuit board (A3) mounting screws -one

near the rear and six near the front.

()3. Swing the CHI Readout circuit board out of the way to gain access to

the back of the Amplifier circuit board (A2)

()4. Amplifiers in the serial number range B050000 to B109999 only: Cut

and remove the two runs on the back of the Amplifier circuit board

as shown in Fig. 1.

040-0785-01 page A

NOTE

The runs to be removed are located under

the CHI VARIABLE (CAL IN)/ GAIN

potentiometer-switch combination. Removal of

the combination will facilitate access to the

circuit board runs.

Fig. 2. Partial -Amplifier circuit board (component side)

Place the CHI Readout circuit board on the Volts/DIv cam switch

bearings and secure the circuit board with the seven screws removed

above.

For steps 6through 15, refer to Fig. 2.

On the front (component) side of the Amplifier circuit board, cut and

remove the run between C2721, a5-25pF variable capacitor, and

R2721, a27n, 0. 25W resistor.

040-0785-01 page 5

Remove C2721 and R272K

Remove Cl 721. a5-25pF variable capacitor, and R1721. a25n.

0.25W resistor, located near U1750,

Unsolder and lift the ends of R1720 and R1723 (both 1.37kn

resistors) which connect to pin 2and 3. respectively, of U1750.

Trim the leads of the four 15n resistors. Included In the kit. to about

3/16 (0. 1875) Inch.

Add R1722 and R1724. two of the 15n resistors. In series between

the lifted ends of R1720/R1723 and the circuit board pads from which

the ends were lifted.

Add Cl 721. one of the 5-25pF variable capacitors included In the kit.

between the junctions of R1720/R1722 and R1723/R1724.

Unsolder and lift the ends of R2720 and R2723 (both l,3kn) nearest

U2750.

Add R2722 and R2724. the two remaining 15n resistors. In series

between the lifted ends of R2720 and R2723 and the circuit board

pads from which the resistors were lifted.

Add C2721. the remaining 5-25pF variable capacitor, between the

junctions of R2720/R2722 and R2723/R2724.

Replace the faulty amplifier microcircuit (U1350. U1450. U1550,

U1750. U2350. U2450. U2550 or U2750) with the microcircuit

provided In the kit.

Refer to the Calibration Section (5) In the 7A26 Instruction Manual

and check instrument performance. making any necessary

adjustments. The attached manual Insert contains supplemental

calibration Information.

NOTE

In order to optimize the lOOHz to lOOkHz

square wave response (low-frequency

compensation) .several components may need

to be selected. If U1350. U1450 or U1550

has been replaced. C1332. R1332. C1431.

R1341 or Cl 436 may need to be selected.

Replacement of U2350. U2450 or U2550 may

require selection of C2332. R2332. C2431.

R2431 or C2436. In some cases, removal of

C2533 may be desirable.

040-0785-01 page 6

()18. Remove the protective backing from the 040-kit label (included in the

kit) and apply It to the top frame section. The label indicates the

installation of this kit for future reference,

()19. Install the electrical shields.

()20. Attach the included manual insert to the Instruction Manual.

REH:rh

040-0785-01 page 7

Product Modification Kit

SUGGESTION/CORRECTIOIM FORM

DATE

KIT NUMBER STEP/PAGE

FIGURE NUMBER PUBLICATION DATE

DISCREPANCY

SUGGESTED CORRECTION /COMMENTS

SUGGESTED BY; NAME /ORGANIZATION

DREPLY REQUESTED

RETURN TO LOCAL FIELD OFFICE /SERVICE CENTER

FIELD OFFICE /SERVICE CENTER /DEL. STA.

SERVICE CENTER: RETURN TO FIELD MODS 73-860

im WILL MAKE CHANGE IMMEDIATELY

[H WILL MAKE CHANGE AT NEXT PRINTING

nOTHER

SIGNED DATE

TEKTRONIX

MANUAL MODIFICATION INSERT

VERTICAL AMPLIFIER MICROCIRCUIT REPLACEMENT

for

7A26 Serial Numbers BOlOlOO -B139377

Installed in SN Date

This modification Insert is provided to supplement the manual

for the above listed product(s). The Information given in

this insert supersedes that given in the manual.

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

This kit provided parts and instructions to replace one of the

vertical amplifier microcircuits. For instruments in serial

number range B010100 to B109999. the emitter compensation

networks for U1750 and U2750 were modified.

In order to optimize the lOOHz to lOOkHz square wave

response (low-frequency compensation), several components

may have been selected. For Replacement of U1350. U1450

or U1550. changes in the values of C1332. R1332. C1431.

R1431 or Cl 436 may have been required. Selection of

C2332. R2332. C2431 or C2436 may have been necessary if

U2350. U2450 or U2550 was replaced. In some cases,

removal of C2533 may have been beneficial.

040-0785-01 page 1

REPLACEABLE ELECTRICAL PARTS

CKT. NO.

C1721

C2721

R1721

R1 722

R1724

R2721

R2722

R2724

*U1350,

PART NUMBER DESCRIPTION

Capacitor, var. cer. 5-25pF lOOV

281-0123-00

DELETE

315-0150-00

DELETE

315-0150-00

155-0078-10

Resistor, cmpsn.

15n 5% 0.25W

150 5% 0.25W

Microcircuit, linear, vertical amplifier

U1450. U1550. U1750. U2350. U2450. U2550 or U2750

—vw /5

C/7Z/

IZIJZ3

Mp/o

UI750

“AAA/—

Partial -CHI AMPLIFIER schematic

Asimilar schematic applies to

channel 2. The first digit in

each circuit number changes

to 2. e.g. C2721,

040-0785-01 page 2

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