230 Chapter4
Troubleshooting the Analyzer
Troubleshooting the A2 Display Assembly
4. Verify the High-Power-Up signal from the A8 power supply by
checking for the +5 V TTL WRUP signal at pin 54 on the A16J1. The
A16J1 connector is on the trace side of the A16 processor/video
assembly. Refer to Figure 4-5 for the numbering order of A16J1
connector-pins accessible from the component side of the A16
processor/video assembly.
Note that the A8 power supply assembly sends the high-power-up
(WRUP) signal to the A16 processor/video assembly after it receives
the low-power-on (LPWRON) signal and the +5 V supply has
stabilized. If WRUP is low, the display remains blank and the A16
failure LEDs (DS1 through DS16) will not come on during power-up.
• If the WRUP signal is missing, trace the signal back through the
A15 motherboard to the A8 power supply assembly, pin 37 on
A8J1. Refer to “A15 Motherboard Assembly” in Chapter 5 for the
connector-pin designation of the WRUP signal path.
Note that if your analyzer is an 8590 E-Series, 8591C, or 8594Q
QAM analyzer, the WRUP signal can be measured on pin 55 of
each card-cage slot on the A15 motherboard. Refer to Figure 4-6
for the numbering order of the connector pins on A15J3 through
A15J6.
• If the WRUP signal is present, yet one or more of the A16
processor/video assembly outputs is incorrect, suspect a defective
A16 processor/video assembly. Before replacing the A16
processor/video assembly, refer to Chapter 3 in this service guide.
• If all the A16 display outputs are correct, suspect a defective A2
display.
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