Tektronix 7B51 Instruction Manual page 42

2. Check Associated Equipment. 8efore proceeding
with troubleshooting of the Type 7851, check that the
equipment used with this instrument is operating correctly.
Check that the signal is properly connected and that the
probe cable is not defective. The indicator oscilloscope and
vertical plug·in unit can be checked for proper operation by
substituting another time·base unit which is known to be
operating properly (perferably another Type 7851 or simi-
lar unit). If the trouble persists after substitution, the indi-
cator oscilloscope and/or vertical plug-in unit is defective.
3. Check Instrument Calibration. Check the calibration
of this instrument, or the affected circuit if the trouble
exists in one circuit. The apparent trouble may only be a
result of misadjustment and may be corrected by calibra-
tion. Complete calibration instructions are given in the Cali-
bration section.
4. Visual Check. Visually check the portion of the in-
strument in which the trouble is located. Many troubles can
be located by visual indications such as unsoldered con-
nections, broken wires, damaged components, etc.
Composition Resistors:
Ceramic Capacitors:
00
and
0
-1 st, 2nd and 3rd significant figures;
®
-multiplier;
CD
-tolerance;
Maintenance-Type 7851
5. Isolate Trouble to a Circuit. To isolate a trouble to a
circuit, note the trouble symptom. The symptom often in-
dicates the circuit in which the trouble is located. For ex-
ample, if normal triggering can be obtained in the EXT
mode but cannot be obtained in the INT mode, the trigger
pre-amp or the input coupling circuit is probably at fault.
When trouble symptoms appear, use the front-panel con-
trols and the CRT display to try to isolate the trouble to
one circuit. When the trouble appears in more than one
circuit, check all affected circuits by taking voltage and
waveform readings.
Fig. 4-2 provides a guide to aid in locating a defective
circuit. This chart does not include checks for all possible
defects; use steps 6 and 7 for further troubleshooting. Start
from the top of the chart and perform the given checks on
the left side of the page until a step is found which is not
correct. Further checks and/or the circuit in which the
trouble is probably located are listed to the right of this
step.
After the defective circuit has been located, proceed
with steps 6 and 7 to locate the defective component(s).
Color
Resistor and Capacitor Color Code
Signifi-
1 _ _
Multiplier
I
.cant I Resis- I Capaci-j
Figures
_t~
tors
Tolerance
Resis- Capaci-
tors tors
Silver
I I
10-
2
I
+10%
:-------r--~~-r---------
Gold
I I
10.
1
I
+5%
Black I 0
:1-
--=-1--I---=---+------'-=--:-+-2::-:0:-:%-:-0-o-r-
2 pF*
Brown I I 10 10 + 1 % + 1 % or
0.1 pF*
~-I
2
I
10 2 10 2 +2% +2%
Orange
I
3
I
10
3
10
3
+3% ±3%
::~:~
I I : II::
L:::
1:~:1
__
: _ - ; _ l ~ - ' - ~ - = - ~ - r -
I~I
0.5pF*
Blue
I
6
1~:_10_6_:
_____
1 _ - - - _ 1
Violet
I
7
I~
Gray
-20%
8 I 10.
2
+80%
or 0.25 pF*
White 9
1:---'--
1
---c
0 --
1
,-----j1:----1--+-:cc 1
0=-%-:-0
'--o-r- I
-(n-o-ne-)--:----+I----:---:
~~~% I - - ± - - - c - ~ o - c - - P o - - - C ~ o * - o - r - I
1 pF*
*For capacitance of 10 pF or less.
®
-temperature coefficient. NOTE:
0
and/or
@
color code for capacitors depends upon
manufacturer and capacitor type. May not be present in some cases.
Fig. 4·1. Color-code for resistors and ceramic capacitors.
®
4-3