General Maintenance
Frequencies ar
e shown in the Top Section – read carefully! These tests do not
show a pass/fail result, even if zero. Measurements are relative to the 25 MHz
VGA clock. Refer to Table below to see the limits for the frequencies. (See
Table 4-8.)
The Middle section shows pass/fail tests. These are mainly bus tests between
FPGAs, Memory, CPU, etc. Some tests cover buss es from an option board to
the main board. In this case it is difficult to tell which end is at fault. Generally
there will be multiple failures, so the most likely cause is evident. If not, the
best path m
ay be to replace the option card first. If that does not fix the problem
then replace the main board.
The botto
m section of the diagnostics results screen shows bus activity for the
SDI input bus and the display bus from the processor to the FPGA. The SDI
bus activity indicators may not move for some test signals; use 10 bit bars or
sweep. Also, SD inputs only have 10 active bits on the Deserializer bus, while
HD has 20 bits. The unit will stay in SD or HD mode, a s it was before the ADV
diagnostic mode was initiated.
The last section of the Advanced Diagnostic Screen are the color ramps at the top
and bottom of the screen. These can be used to check the bits provided to the
LCD. I
f any bits are missing then you will see banding in the ramps. It is normal
to see some bands about
1
/
8
inch (2 mm) wide, especia lly near the lower intensity
regions of the ramp. This is because the LCD is only 6 bits, s o there are 64 steps
in the ramp. However, any larger steps or any non-monotonic regions indicate a
problem. Check the cable to the LCD, perform the LCD diagnostic procedure,
or replace the display assembly. It is also possible for the m ain board to cause
pro
blems in this area.
Table 4-8: Advanced diagnostic measurements
Measurement Min Max
VGA Clock
64.4375 MHz 64.4575 MHz
QDR Clock
25.1650 MHz 25.1850 MHz
SD Eye
35.9844 MHz 36.0564 MHz
HD Eye 59.3106 MHz 59.4924 MHz
Audio PLL 1 12.2780 MHz 12.2980 MHz
Audio PLL 2 12.2780 MHz 12.2980 MHz
HSYNC PW
20.4 μs 20.8 μs
VSYNC PW
18974.9 μs 19174.9 μs
Lissajous 61.3900 MHz 61.4900 MHz
Isolating Advanced
Diagnostic Lissajous
Errors
The advanced diagnostics tests the lissajous data path between the audio and main
boards. A failure in this data path can be due to a problem on either board.
Perform the following tests to isolate the problem to one board or the other.
4–20 WFM6120, WFM7020, and WFM7120 Waveform Monitors Service Manual
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