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Model 415E
Section V
Paragraphs 5-23 to 5-31
5-23. ETCHED CONDUCTOR REPAIR.
A broken or
burned section of conductor can be repaired by bridging
the damaged section with a length of tinned copper
wire.
Allow adequate overlap and remove any var¬
nish from etched conductor before soldering wire
into place.
5-24. TRANSISTOR REPLACEMENT.
a. Do not apply excessive heat. See Table 5-3 for
soldering tool specifications.
b. Use a heat sink such as pliers or hemostat be¬
tween transistor body and hot soldering iron.
c. When installing a replacement transistor, ensure
sufficient lead length to dissipate heat of soldering by
maintaining about the same length of exposed lead as
used for original transistor.
5-25. DIODE REPLACEMENT.
5-26. Solid state diodes are in many physical forms.
This sometimes results in confusion as to which lead
or connection is for the cathode (negative) or anode
(positive), since not all diodes are marked with the
standard symbols. Figure 5-2 shows examples of some
diode marking methods. If doubt exists as to polarity,
an ohmmeter may be used to determine the proper
connection. It is necessary to know the polarity of the
ohms lead with respect to the common lead for the
ohmmeter used. (For the hp Model 410B Vacuum Tube
Voltmeter, the ohms lead is negative with respect to
the common; for the hp Model 412A DC Vacuum Tube
Voltmeter, the ohms lead is positive with respect to the
common.) When the ohmmeter indicates the least diode
resistance, the cathode of the diode is connected to the
ohmmeter lead which is negative with respect to the
other lead.
Note: Replacement instructions are the same
as those listed for transistor replacement.
5-27. SWITCH REPAIR OR REPLACEMENT.
5-28. The EXPAND and RANGE switches are on the
same assembly, as are the GAIN and VERNIER con¬
trols.
These assemblies, along with the POWER
switch and the INPUT switch, may be removed by first
taking off all instrument covers and using the appli¬
cable instructions which follow.
Note:
For general soldering instructions,
refer to Paragraph 5-24 and 5-25.
5-29. GAIN/VERNIER.
Refer to Figure 5-3 and the
schematic diagrams for component identification and
location.
a. Loosen setscrews in knobs and remove from
shaft.
b. Loosen and remove shaft nut from front panel.
c. Pull assembly back and out of instrument re¬
moving lock washer and grounding lug from shaft.
Also remove white GAIN/VERNIER instruction plate
from front panel.
d. Unsolder connecting wires. Mark each to indicate
which lugs to resolder wires to.
e. Replacement is reverse of removal.
5-30. RANGE-DB/EXPAND. Refer to Figure 5-3 and
the schematic diagram for component identification
and location.
a. Loosen setscrews in knobs and remove from
shaft.
b. Loosen and remove shaft nut from front panel.
c. Loosen the BANDWIDTH potentiometer to allow
the switch assembly to be pulled free of the front panel.
d. Unsolder connecting wires. Mark each to indicate
which lugs to resolder wires to.
e. Replacement is reverse of removal.
5-31. INPUT. Refer to Figure 5-3 and the schematic
diagrams for component identification and location.
a. Loosen setscrews in knob and remove fromshaft.
b. Loosen and remove shaft nut from front panel.
c. Pull switch assembly free from front panel and
unsolder connecting wires.
Mark each to indicate
which lugs to resolder wires to.
d. Replacement is reverse of removal.
5-32. POWER. Refer to Figure 5-3 and the schematic
diagrams for component identification and location.
a. Loosen the two nuts holding circuit board in place
and remove circuit board from instrument.
b. Loosen setscrews in knob and remove from shaft.
c. Loosen and remove shaft nut from front panel.
d. Pull switch assembly free from front panel and
unsolder connecting wires.
Mark each to indicate
which lugs to resolder wires to.
e. Replacement is reverse of removal.
DIODE SYMBOL
ANODE-H-CATHODE
Figure 5-2. Examples of Diode Marking Methods
02152-1
5-9
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