GE LOGIQ E9 Service Manual page 498

PROPRIETARY TO GE
D 5180483-100, R . 7 LOGIQ E9 P S M
IRECTION EV ROPRIETARY ERVICE ANUAL
7-9-19-7 Visual Inspection of Board (cont'd)
Troubleshooting Step 2 - Upper and Lower Transmit Bank (cont'd)
Figure 7-199 Check in near Field Image
A dark streak in the near field, indicates either a defective Front Plane or the transducer itself has been
damaged. Save image to the clipboard, swap the Front Plane locations, reproduce the saved image and
compare. If images are the same, the transducer is bad. If there is one dark streak and it moved, the
Front Plane is bad. If two dark streaks appear, both the transducer and the Front Plane are most likely
defective.
In very uncommon cases, it has been seen that there was no physical damage apparent and the T/R
Channel Test and Analog Rx diagnostics will pass, but there is a dark streak in the near field of the
image.
In this case, typically only one half of the transmit waveform is being seen at the transducer. This is
caused by one of the blocking diodes on a Front Plane being open.
It is important to use a known, good transducer to troubleshoot this type of failure mode.
Make sure the Front Planes and GTX Boards are marked for their original positions.
Remove GTX1 and GTX2, so only GTX3 is imaging in the system. Install the Front Planes in their
original positions and check the near field image. There should be one dark streak. Save this image to
the clipboard for reference.
Swap the Front Planes and check the near field image. If there are now two dark streaks, this is the
defective GTX Board.
If one dark streak is apparent, rotate the remaining GTX Boards through slot 3 and repeat the test until
the case of two dark streaks is seen.
If two dark streaks are seen with multiple GTX Boards, this may indicate a defective GRX Board.
Chapter 7 Diagnostics/Troubleshooting 7 - 295