Measurement Error Troubleshooting Hints - Tektronix 2246 1Y Service Manual

Maintenance—2246 1Y and 2246 Mod A Service
Conditions:
All vertical channels can be successfully dis­
played and positioned independently.
The A and B sweeps both free-run and trigger
successfully.
Both A and B Trigger COUPLING and SOURCE
operate properly.
Normal-appearing readout text and cursors can
be displayed.
Definition of terms:
Type 1 volts measurements are:
l<- VOLTS-H and rk VOLTS-H
Type 2 volts measurements are:
DC
Type 3 volts m easurem ents are:
Circuit
Problem
Ground relay stuck in
signal position
Defective X I 0, X I 00,
X I, X2, X5 Relays
and Attenuators
ZERO HYST line stuck
low (U173-13)
6-26
Table 6-9

Measurement Error Troubleshooting Hints

VERTICAL INPUTS (schem atic Diagram 1)
Gross value problems for Types 1-4 volts measurements.
Gross value problems A TL and B TL.
Test: Use " EXERCISE VOLT REF." Check that the ground relay is in
ground position.
Gross value problems for affected channel for Types 1-4 volts
measurements.
Gross value problems in A TL and B TL.
Test: Check channel accuracy at all VOLTS/DIV settings.
In Type 4 measurements, minor value problems for +PK cursors
when gating interval is at negative end of waveform, and for
-PK cursors when gating interval is at positive end of waveform.
Test: Turn off all measurements; use the A Horizontal Mode. U431
pin 28 should be -3 .0 volts.
Switch to ALT Horizontal Mode. U431 pin 28 should be -0 .7 volts.
+PEAK, -PEAK, PK-PK
Type 4 volts measurements are:
GATED +PEAK, GATED -PEAK, and GATED
PK-PK
Measurement value accuracy is the accuracy of
number displayed in top line of readout on the
crt.
Measurement cursor accuracy is the accuracy
of the match between cursor position and the
measurement value.
Trigger value accuracy is the accuracy of the
number displayed on the trigger level cursor.
Trigger cursor accuracy is the accuracy of the
match between cursor position the value dis­
played on the cursor.
A TL is the A trigger level measurement system.
B TL is the B trigger level measurement system.
Symptoms