HP 70908A, Service Manual

Page: 66 / 335

If Hardware Error Messages (7000{7999) Occur
If Hardware Error Messages (7000{7999) Occur
Hardware errors are generated when a module in the HP 70000 Series modular spectrum
analyzer system is not working properly . These errors can occur at any time . Hardware errors
range from 7000{7999. Troubleshoot these errors in the order reported by the HP 70900B local
oscillator source .
One or more of the following hardware error messages may appear on your system display:
7000 ROM check error
This hardware error occurs when there is a dierence between the programmed
checksum and the computed checksum for the lower 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.)
7002 1st LO unleveled
This hardware error indicates an unleveled 1st LO signal. It occurs when the voltage
at A13U4 pin 1 on the A13 ALC/bias goes positive . If that point goes slightly positive ,
it will cause the output of A13U4 to swing all the way to its positive rail. This voltage
is sent to the A12 controller where it is monitored by A12U19 (TTL low = error
condition).
T o solve this problem:
1. Check that the LO IN signal is actually getting power to the RF section. This
normally comes from the HP 70900B local oscillator source LO . The power level
should be between +4 and +12 dBm.
2. Check that the power into the A1 leveling amplier is between +4 and +12 dBm.
3. If correct, troubleshoot the A1 leveling amplier . (Refer to \Troubleshooting the
A1 Leveling Amplier ".)
4. 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.)
7003 2nd LO unlocked
This hardware error occurs when the voltage at A9TP1 (A9 2nd converter PLL)
exceeds a 08.8 V to +8.6 V range . This voltage is sent to A12TP2-1 (A12 controller )
where it is sensed, translated to TTL, and read by the controller . A TTL low measured
at A12TP2-1 indicates a locked condition.
T o solve this problem:
1. P erform the 2nd converter alignment adjustments .
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.)
T roubleshooting 4-5