Troubleshooting Equipment; Troubleshooting Procedure - Tektronix 7D11 DIGITAL DELAY Service Instructions Manual

Maintenance-7D11 Service
The insulated wires used for interconnection in the
7Dll are color coded to facilitate tracing a wire from one
point to another in the unit.
Semiconductor Lead Configuration. Fig. 6-1 shows the
lead configuration of the sem iconductor devices used in this
instrument.
Troubleshooting Equipment
The following equipment is useful for troubleshooting
the 7Dll:
1. Semiconductor Tester-Some means of testing the
transistors, diodes, and FET's used in this instrument is
helpful. A transistor-curve tracer such as the Tektronix
Type 576 will give the most complete information.
2. DC Voltmeter and Ohmmeter-A voltmeter for
checking voltages within the circuit and an ohmmeter for
checking resistors and diodes are required.
3. Test Oscilloscope-A test oscilloscope is required to
view waveforms at different points in the circuit.
A Tektronix 7000-series Oscilloscope with 7D 13 Digital
Multimeter unit, 7B-series Time-Base unit, and a 7 A-series
Amplifier unit with a lOX probe will meet the needs for
items 2 and 3.
Troubleshooting Procedure
This troubleshooting procedure is arranged in an order
which checks the simple trouble possibilities before pro-
ceeding with extensive troubleshooting.
1. Check Control Settings. I ncorrect settings of the
7Dll controls can indicate a trouble that does not exist. If
there is any question about the correct function or
operation of a control or front-panel connector, see the
Operating I nstructions section.
2. Check Associated Equipment. Before proceeding
with troubleshooting of the 7Dll, check that the equip-
ment used with this instrument is operating correctly. If
possible, substitute a 7D 11 known to be operating correctly
into the indicator unit and see if the problem persists.
Check that the inputs are properly connected and that the
interconnecting cables are not defective.
3-2
3. Visual Check. Visually check the portion of the
instrument in which the trouble is suspected. Many troubles
can be located by visual indications, such as unsoldered
connections, broken wires, damaged circuit boards, dam-
aged components, etc.
4. Check Instrument Performance. Check the cali-
bration of the unit, or the affected circuit by performing
the performance check of Section 4. The apparent trouble
may only be a result of misadjustment and may be
corrected by calibration. Complete calibration instructions
are given in Section 4.
5. Check Voltages and Waveforms_ Often the defective
component or stage can be located by checking for the
correct voltage or waveform in the circuit. Typical voltages
and waveforms are given on the diagrams; however, these
are not absolute and may vary slightly between instru-
ments. To obtain operating conditions similar to those used
to take these readings, see the instructions in the Diagrams
section.
6. Check Individual Components. The following
methods are provided for checking the individual compo-
nents in the 7 D 11. Components wh ich are soldered in place
are best checked by disconnecting one end to isolate the
measurement from the effects of surrounding circuitry.
A. TRANSISTORS AND INTEGRATED CIRCUITS.
The best check of transistor and integrated circuit oper-
ation is actual performance under operating conditions. If a
transistor or integrated circuit is suspected of being
defective, it can best be checked by substituting a compo-
nent known to be good; however, be sure that circuit
conditions are not such that a replacement might also be
damaged. If substitute transistors are not available, use a
dynamic tester (such as Tektronix Type 576). Static-type
testers may be used, but since they do not check operation
under simulated operating conditions, some defects may go
unnoticed. Be sure the power is off before attempting to
remove or replace any transistor or integrated circuit.
Integrated circu its can be checked with a voltmeter, test
oscilloscope, or by direct substitution. A good under-
stand ing of the circuit description is essential to trouble-
shooting circuits using integrated circuits. Use care when
checking voltages and waveforms around the integrated
circuits so that adjacent leads are not shorted together. An
integrated-circuit test clip provides a convenient means of
clipping a test probe to the 14- and 16-pin integrated
circuits. This device also doubles as an integrated-circuit
extraction tool.
B. DIODES. A diode can be checked for an open or for
a short circuit by measuring the resistance between termi-
REV. B, AUG. 1975