Tektronix WFM6120 Service Manual

General Maintenance
Detailed Troubleshooting Procedures
The following tests should b e run as indicated in the Symptom and Causes table.
(See Table 4-4 on page 4-7.). The procedures check for specificproblemsor
will help you isolate a problem to a board. You can run them at any time for
informational purposes but if you do not run the procedures in the correct context,
then the fina
l recommendation identifying a root cause might be suspect.
List of detailed troubleshooting procedures:
General Checks
Primary Power Supply Checks
Secondary Power Supplies Checks
Front Panel Troubleshooting
Isolating Audio Problems
Isolating Advanced Diagnostic Lissajous Errors.
General Checks
1. Verify that the p ower cord is connected.
2. Check t hat all internal cables are correctly connected and seated.
3. Check for any discolored or burned components.
Fan Failures
The Fan is controlled by both hardware a nd software. Hardware controls the
fan to a certain speed, but software sets the speed target as a function of the
temperature measured on a variety of temperature sensors.
If the fan fails, then LED DS861 on the Main board will be lit.
The fan failure is sensed through tachometer feedback, thus a fault will be asserted
if the fan is not connected, is stalled, or if the tachometer feedback line is not
working correctly.
If the fan fails, the control circuit will increase the voltage to the 13.5 V max level.
The normal voltage to drive the fans (pin 1) varies from about 6 V to 13.5 V in
response to tempe rature and fan speed.
If the fan is not spinning, measure the voltage on the fan connector J890 pin 1. If
the voltage is near 13 V then replace the fan.
If the voltage is not above 10 V then replace the main board.
If the fan is spinning, but LED DS861 is lit, the problem is probably the tachometer
feedback line on pin 3 of the fan. Inspect the wiring a
nd pull-up resistor R864 on
the main board, and use the oscilloscope to look for a 3.3 V square wave on the
tachometer feedback line. Replace the fan if the pull up is intact but there is no
signal on the tachometer line
WFM6120, WFM7020, and WFM7120 Waveform Monitors Service Manual 4–13

Tektronix WFM6120 Specifications

General

Brand	Tektronix
Model	WFM6120
Category	Monitor
Language	English