Troubleshooting Aids; Troubleshooting Techniques - Tektronix 1S1 Instruction Manual

Installation:
1. Reverse the order of removal to install a new etched-
wiring board.
2. Resolder all wires to the board according to the sol-
dering technique described previously. Wire locations and
color-coding of all wires are shown in Figs. 4-3, 4-4 and 4-5.
Gate Diodes. The diodes in the sampler gate and mem-
ory gate are special gallium arsenide diodes manufactured by
Tektronix. The sampler gate diodes occasionally cause
poor risetime or system noise. The memory gate diodes
sometimes cause memory dot slash. None of these diodes
should be replaced, however, unless all other possible
sources of trouble have been eliminated. Close matching is
required and several of the critical characteristics of the
system are affected.
Each diode has a colored dot on the cathode end. The
color of the dot identifies its use in the instrument, as indi-
cated in Table 4-1.
The circuit number and polarity of each diode is shown
on the schematic diagram and is also marked on the etched-
wiring board near the diode mounting assembly.
If it is necessary to remove or replace any of the gallium
arsenide diodes, use a pair of tweezers or a tweezer-type
tool. Do not solder the diodes into their clips.
Gallium Arsenide Diodes
Dot Color Circuit Number
Yellow D11B, D11C
Orange D11A, D11D
Red D110, D112(pair)
*D11A and D11C supplied by Tektronix as a matched pair;
D11B and D11D supplied as a matched pair
Rotary Switches. Individual parts or sections of rotary
switches normally are not replaced separately. If a switch
is defective, the entire assembly should be replaced. Order
the switch either with or without the associated components
wired in place. Part numbers are given in the electrical
portion of the Parts List.
Tag the leads and switch contacts with corresponding
identification tags as the leads are disconnected, then use
the old switch as a model for installing the new one. When
soldering the leads to the new switch, do not let the solder
flow beyond the rivet on the switch terminal. Spring tension
of the switch contact will be destroyed by excess solder.
TROUBLESHOOTING
This portion of the Maintenance section is provided to
aid in locating and correcting trouble in the Type 1S1.
Information contained in the circuit description, the calibra-
tion procedure and the schematic diagrams is also helpful
when troubleshooting the instrument.

Troubleshooting Aids

Diagrams. Circuit schematic diagrams are given on fold-
out pages in Section 6. The circuit numbers and electrical
Table 4-1
Tektronix
Part No.
152-0216-00*
152-0083-00
.
values of all components, as well as significant voltages
and waveforms, are shown on the diagrams. All front-panel
and internal control names are given and all coax con-
nectors and input and output leads are indicated. The
components of each subcircuit are assigned related circuit
numbers so they can be easily located on the diagram.
The sections of rotary switches are coded on the diagrams
to indicate the physical positions of the switch contacts.
The sections are numbered from the front panel to the rear
of the assembly. If two switches (such as the TIME/CM
and TIME POSITION RANGE) are mounted as a single
unit, a single sequence of numbers is used for the entire
assembly. The letters F and R indicate whether the front
or rear of the section is used to perform the particular
switching function. For example, 3R refers to the rear side
of the third switching section back from the front panel.
Etched-Wiring Boards. Due to the high-density spacing
of components on the etched-wiring boards, only a few
component circuit numbers are printed on the boards.
However, all components and connections on the boards
are shown in Figs. 4-3 through 4-5. Test points can be
located where they connect to one or more of the com-
ponents.
Wiring Color-Code. All insulated wire in the Type 1S1
is color-coded for convenience in circuit tracing. Signal-
carrying leads are identified with one or two colored stripes.
Voltage-supply leads are coded with three stripes to indicate
the approximate voltage carried by the lead, using the
standard EIA resistor color code. The code is read starting with
the widest stripe and proceeding in order of decreasing
width. A white background indicates a positive voltage and
a tan background indicates a negative voltage. As an
example, coding on the -19-volt lead is red (widest stripe),
black and black (narrowest stripe) on a tan background.
Note that this coding reads -20 volts, which is the closest
value that can be easily identified with the color code.
Resistor Color-Code. In addition to the brown compo-
sition resistors, some metal-film resistors (identifiable by their
gray body color) are used in the Type 1S1. Both of these
types are coded for resistance value with the EIA color-
code, which is read starting with the stripe nearest the
end of the resistor. The composition resistors have four
stripes which consist of two significant figures, a multiplier
and a tolerance value. The metal-film resistors have five
strips which consist of three significant figures, a multiplier
and a tolerance value. The values of wire-wound resistors
(light blue or gray-green) are marked on the body of the
component.

Troubleshooting Techniques

The following procedure is arranged in a sequence to
check operational troubles before proceeding with extensive
troubleshooting. If the trouble is not located by the checks,
the remaining steps will help locate the defective part or
parts. When replacing any defective parts, follow the re-
placement procedures described earlier in this section.
1. Check Control Settings. Incorrect control settings can
indicate trouble that does not exist. For example, incorrect
setting of the triggering controls for the particular input
signal may seem to indicate a defective trigger circuit. If
there is any question about the correct purpose and use of
Maintenance – Type 1S1
4-3