HP 70908A, Service Manual

Page: 67 / 335

If Hardware Error Messages (7000{7999) Occur
7004 300 MHz error
This hardware error occurs when the detected level of 300 MHz at A11J2 falls below
the reference voltage set by A11CR5 (about 0.3 V). Capacitor A11C46 charges up
to a voltage proportional to the 300 MHz input power , and that voltage is sensed
at A11U4A. The output of A11U4A is sent to the A12 controller where the error
condition (TTL low) is reported to the master module of the spectrum analyzer .
T o solve this problem:
1. V erify that the 300 MHz signal is actually getting to the RF section. This normally
comes from the HP 70900B local oscillator source LO . The power level should be 0
62 dBm.
2. Troubleshoot the A11 last converter . (Refer to \Troubleshooting the
A11 Last Converter ".)
3. If necessary , obtain service from Hewlett-P ackard. (Refer to \If Y ou W ant
Hewlett-P ackard to Service Y our RF Section " in Chapter 1.)
7009 ROM #2 check error
This hardware error occurs when there is a dierence between the computed
checksum and programmed checksum of the upper half of the addresses of A12U7.
T o solve this problem:
1. Replace A12U7.
2. If problem remains , troubleshoot the A12 controller . (Refer to \Troubleshooting the
A12 Controller".)
3. If necessary , obtain service from Hewlett-P ackard. (Refer to \If Y ou W ant
Hewlett-P ackard to Service Y our RF Section " in Chapter 1.)
7033 P ower supply fault
This hardware error occurs when any of the power supply sense lines to A10U191 or
U192 fall below +2.5 V . This happens when a supply is loaded down.
T o solve this problem:
1. Troubleshoot the A10 power supply/driver . (Refer to \Troubleshooting the
A10 P ower Supply/Driver".)
2. If necessary , obtain service from Hewlett-P ackard. (Refer to \If Y ou W ant
Hewlett-P ackard to Service Y our RF Section " in Chapter 1.)
4-6 T roubleshooting