Troubleshooting Hints By Diagram - Tektronix 2246 1Y Service Manual

Error Label

TROUBLESHOOTING HINTS BY DIAGRAM

Vertical SELF CAL—Checks Cursor and
Preamplifier Outputs
The circuitry listed below must be operational for
Vertical SELF CAL to work. Troubleshoot these cir­
cuits if voltage measurements or tracking cursors
are not correct.
1. DAC system (U2303,
Diagram 11).
2. Trigger Level Comparators (U431 and U421,
Diagram 3).
3. VERT COMP feedback (U702, Diagram 2).
4. ECL-to-CMOS translators (Q604, Q605, Q606,
Q607, Q602, and Q603) between U600 and U602
(Diagram 4).
5. Data to Measurement Processor (data bus and
bus transceivers, Diagram 8).
6. VOLTS CAL signal (U931, Diagram 7).
Table 6-6 (cont)
DIAGNOSE ROUTINES
Path, devices tested, and troubleshooting actions
Time Base
Cal Signal
128 AS
8.192 ms
256 AS
4.096 ms
2.048 ms
512 AS
32.768 ms
1.024 ms
64 AS
32 AS
Check U421, U431, U1106A, and associated circuitry, Diagram 3.
SLIC (Display Logic 1C, U600) and FLIC (Trigger Logic 1C, U602) gate
outputs and level shifters, Diagram 4.
U2304, and U2305,
Maintenance—2246 1Y and 2246 Mod A Service
Code
0
1
2
3
4
5
6
7
13
14
7. Vertical Preamps (U210,
U240), Delay Line Drivers (Q250, Q251, Q252,
and Q253), and Vertical
circuitry (U203, U801B, U201, U202, U280, Q284
and Q285, Diagram 2).
HORIZONTAL SELF CAL-Checks Sweep Timing
1. Put the oscilloscope into Self Cal and check at
U421A pin 4 (Diagram 3) for changing width
calibration signals.
2. Run the " EXERCISE TIME REF" exerciser and
check for correct TB CAL signal at U421A pin 4,
Diagram 3 (see Table 6-5).
Schematic Diagram 1—Vertical INPUTS
1. Run DIAGNOSE to check for shift register failure.
2. Run the shift register exerciser for Shift Register
0. Check for clock, data, and strobe signals.
Check the shift register outputs.
NOTE
The outputs of U171 and U172 are at 15 V;
the outputs from U173 are at 5 V.
U220, U230, and
Position Switching
6-19