Tektronix 7A19 Instruction Manual page 16

Maintenance---7A19
Semiconductor Replacement . Transistors and integrated
circuits (IC's) should not be replaced unless actually
defective if removed from their sockets during routine
maintenance, return them to their original sockets . Unnec-
essary replacement of semiconductors may affect the
calibration of this instrument . When semiconductors are
replaced, check the performance of the part of the
instrument which may be affected .
Replacement semiconductors should be of the original
type or a direct replacement . Lead configuration of the
semiconductors used in this instrument are shown on the
schematic diagrams . If the replacement semiconductor is
not of the original type, check the manufacturer's basing
diagram for proper basing .
TEKTRONIX Integrated Circuits . If it should become
necessary to replace the TEKTRONIX integrated circuits
U40 and U100 use the following procedures :
1 . Remove the common heat sink (No . 64 in Fig . 1
EXPLODED of the Mechanical Parts List section) .
2 . Unsolder the two ground straps from either side of
the integrated circuit case and unplug the integrated circuit .
3 . To install, align the tab of the integrated circuit with
the dot, marked on the circuit board . Then, making sure
pins are aligned with their sockets, gently push into the
socket .
Inductor Replacement
(L21, L22, L81, L82, L124,
L125) . Inductors are replaced as a pair along with their
associated capacitor (e .g ., L21, L22, and C20) . The
inductors are formed by the leads of the capacitor, see Fig .
4-1 . To replace a pair of inductors, proceed as follows :
Fig . 4-1 . Inductor ("T" coil) replacement .
4-4
NOTE
The leads of the integrated circuit are cut at the
factory to prevent the integrated circuit from resting
directly on the circuit board. Defeating this purpose
may allow the pin sockets to short against the
integrated circuit case. Solder the ground leads to the
case and replace the heat sink .
1 . Remove the inductors and associated capacitor by
using a low wattage soldering iron and a vacuum type
desoldering device .
2 . Insert the replacement capacitor on the circuit board
and bend the leads to form a loop approximately 3/8 inch
high .
3 . Solder the capacitor and inductors to the circuit
board .
Replacement of any of the inductors will affect the high
frequency characteristics of the 7A19 and re-calibration
will be necessary .
REPACKAGING FOR SHIPMENT
If the Tektronix instrument is to be shipped to a Tektronix
Service Center for service or repair, attach a tag showing :
owner (with address) and the name of an individual at your
firm that can be contacted, complete instrument serial
number and a description of the service required .
Save and re-use the package in which your instrumentwas
shipped . If the original packaging is unfit for use or not
available, repackage the instrument as follows :
1 . Obtain a carton of corrugated cardboard having inside
dimensions of no less than six inches more than the
instrument dimensions ; this will allow for cushioning .
Refer to the following table for carton test strength
requirements .
2 . Surround the instrument with polyethylene sheeting to
protect the finish of the instrument .
3 . Cushion the instrument on all sides by tightly packing
dunnage or urethane foam between carton and instru-
ment, allowing three inches on all sides .
4 . Seal carton with shipping tape or industrial stapler .
SHIPPING CARTON TEST STRENGTH
REV . A, AUG . 1976
Gross Weight (lb) Carton Test Strength (lb)
0-10 200
10-30 275
30-120 375
120-140 500
140-160 600