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HYDRA
Service Manual
5A-6
Table 5A-1. Error Codes (2635A) (cont)
Error Description
Error 9 A/D Converter Not Responding
This error is displayed if communication cannot be established with the 6301Y Microcomputer
(A3U9).
Error A A/D Converter ROM Test Failure (A3U9)
All bytes of internal ROM for the 6301Y Microcomputer (A3U9) (including the checksum byte) are
summed.
Error b A/D Converter RAM Test Failure (A3U9)
Complementary patterns are alternately written to and read from each location of the 256 bytes of
RAM internal to the 6301Y Microcomputer (A3U9).
Error C A/D Converter Self Test Failure
The Analog Measurement Processor (A3U8) is programmed to do self test measurements.
Error d Memory Card Interface Not Installed
The Microprocessor checks the system at power-up to determine whether the Memory Card
Interface is installed.
5A-4. General Troubleshooting Procedures
Hydra allows for some fault isolation using self-diagnostic routines and descriptive error
codes. However, these features are somewhat limited and do not provide in-depth
troubleshooting tools.
Hydra incorporates a semi-modular design; determining modules not related to a
problem constitutes the first step in the troubleshooting process.
As a first step, remove the Memory Card Interface (A6) from the Hydra Databucket
(2635A). Refer to Section 3 of this manual for removal procedures. If removal of this
assembly results in improved instrument operation, refer to the Memory Card Interface
troubleshooting found later in this section.
Measuring the power supplies helps to isolate a problem further. Refer to Table 5A-2
and Figure 5A-1 for test point identification and readings. If power supply loading is
suspected, disconnect the Display PCA at A1J2. If this action solves the loading
problem, proceed to Display Assembly Troubleshooting elsewhere in this section.
Otherwise, refer to Power Supply Troubleshooting.
Table 5A-2. Preregulated Power Supplies (2635A)
Preregulated Voltage Measurement Points Resulting Supply
-8.9V
-30.9V
+9.2V
-8.6V
A1CR13-2 to A1TP1
A1TP4 to A1TP1
A1CR5 cathode to A1TP30
A1CR7 anode and A1TP30
VEE
VLOAD
VDD, VDDR
VSS
If the power supplies appear to be good, check the Display clock signal (DCLK (A1R85)
and E clock signal (A2U4-1)). This clock signal is not symmetrical; it should be about
+5.0 volts for about 325 nanoseconds and then near 0 volts for about 651 nanoseconds. If
it is not correct at either measurement point, remove the Display Assembly and check
the Display clock again at A1R85. If it is now correct, the problem is most likely on the
Display Assembly. If it is still incorrect, the problem is probably in the Digital Kernel on
the Main Assembly.