Tektronix 2467B - Page 463

Sweep Troubleshooting
STATE PROBABLE CAUSES
1 Trigger signal or Trigger circuit.
2 AUXTRIG input, U700 or U900 pin 3, HI (>3.56 V), or Sweep circuit.
3 Timing current supply to ITREF input (U700 or U900 pin 24). Current mirror comprising U910 and the IT,
ITRR, ITF, and ITR terminals (U700 or U900 pins 12-15). Sweep circuit, U700 or U900.
4 (Floating between -1.25 V and +1.4 V): See state 3.
5 Sweep circuit, U700 or U900. Temporarily exchange U700 and U900.
6 NOTE: In state 6, the sweep will recover to -1.25 V, even though THO (or DG-THOB) remains LO.
A Sweep: SGA path to U650, U650 response to SGA, or THO path.
B Sweep: DG path or generation in U700 (if B Sweep stuck
in state 6).
7 NOTE: If trigger is in a free-run mode, state 8 follows state 6 immediately.
Trigger circuit response to THOA or THOB.
8 THO timer: circuits between U165C and U650 inclusive (A Sweep). Normal rest state for B Sweep.
2465B/2467B Service
The following state table, and timing diagram show the sequence of events from initiation through the execution of the A
sweep. They can be used to troubleshoot a non-operable sweep. If no sweep is present, use an oscilloscope to observe
control signals TGA , TGB , SGA , SGB , THO, DG , and the A or B SWEEP ramp. Note the condition of the signals and
refer to the state table to determine where the sweep is stuck. Then, refer to the probable cause table. Probable cause is
listed by sweep state.
State
0
1
2
3
4
5
6
7
8
Action
Initialize (only
at front-panel
change).
Wait for Trigger
Initiate Sweep Gate
Initate Ramp Up
Run Ramp Up
Nominal
Duration
at 2 /is/div
Indefinite
<20ns
<200 ns
22^s
Terminate Sweep Gate <2 us
Initiate Holdoff
Reset Trigger
RESET SWEEP
(Then return to
state 1 or 2.)
<100ns
<10 ns
2 MS
Sweep States
TGA or,
TGB
(not Trigger
Gate)
U500-18 and
U500-42
HI
LO
LO
LO
LO
LO
LO
HI
SGA or
SGB
(not Sweep
Gate)
U650-15 and
U650-14
HI with THO
HI
HI
LO
LO
LO
HI
HI
HI
THO or
DG
(AorB
Trigger
Holdoff)
U650-13
HI for
5 ms
(Last of
three
pulses
in 240 ms
sequence)
LO
LO
LO
LO
LO
LO
HI
HI
RAMP
U735-9
-1.25 V
-1.25 V
-1.25 V
Slew to
+ 1.36 V
+ 1.36 V
+ 1.36 V
+ 1.36 V
Slew to
-1.25 V
NOTE
When sweep free runs, as in AUTO Mode, STATES 1 and 7 are omitted and TGA remains LO in state 8.
6019-31