Tektronix TG8000 Service Manual

GPS7 module troubleshooting
Internal mode oven test
Perform this pr
ocedure to determine if the oven oscillator is working and within
specifications.
1. Set the GPS7 module under test to internal reference mode.
a. Press the Module button to select GPS7 [1].
b. Press the up (▲)ordown
(▼) arrow buttons to select REFERENCE,
and then press the ENTER button.
c. If necessary, press the up (▲)ordown(▼) arrow buttons to select
SOURCE.
d. Press the left (◄)orright(►) arrow buttons to select Internal,andthen
press the ENTER button.
2. Use the frequency accuracy setup from the TG8000 Specifications and
Performance Verification Technical Reference manual (available on the Web
at www.tektronix.com/downloads) to compare the Black Burst signals from
the instrument under test to the reference unit. An alternate way to check
frequency accuracy follo
ws step 4.
3. Since the instrument under test is in internal mode the timing may shift. The
vector will probably spin relative to the reference unit, which is locked to GPS.
4. Use the timing display to measure how fast the timing is shifting. A 1 μsshift
per second equates to a 1 ppm difference in the time bases of the two units.
Measure the timing shift for a reasonable time and then calculate the frequency
error. For example, a 25 μsshiftin10seconds=25/10=a2.5ppmerror.
Go to step 7.
Alternate procedure:
As an alternative to using a reference TG8000/GPS7 unit, you can use a
frequency counter to determine the frequency error.
5. Connect the frequency counter to the BLACK 3 output.
6. Configure the BLACK 3 output to produce a 10 MHz CW signal.
a. Press the MODULE button to select GPS7.
b. Use the up (▲)ordown(▼) arrow buttons to select SELECT OUTPUT.
c. Press the left (◄
)orright(►) arrow buttons to select BLACK 3.Press
the ENTER button to confirm this selection.
d. If necessary, press the up (▲)ordown(▼) arrow buttons to choose
SELECT FORMAT.
e. Use the left (◄)orright(►) arrow buttons to choose CW 10 MHz. Press
the ENTER button to confirm this selection.
f. Measure the frequency accuracy directly. At 10 MHz, 1 ppm = 10 Hz, so
a measured frequency of 10,000,010 Hz is 1 ppm high.
TG8000 Multiformat Test Signal Generator Service Manual 10–19

Tektronix TG8000 Specifications

General

Brand	Tektronix
Model	TG8000
Category	Portable Generator
Language	English