Agilent Technologies 4352B, Service Manual

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If the A50 SHUTDOWN LED is o, check the cable connection between A50J2 and A2J4.
If the connection is good, continue with the FIND OUT WHY THE A50 SHUTDO WN LED
IS OFF in this chapter .
If the A50 SHUTDOWN LED is on, continue with the Check the A1 +5 VD LED in this
procedure .
Figure 5-1. A50 SHUTDO WN LED Location
A50 Shutdown LED
The A50 SHUTDOWN LED turning o indicates some of A50 power supply is shut down by the
A50 shutdown circuitry .
There are two F AN conditions , rotating and not rotating when the SHUTDOWN LED turns
o. When the fan is rotating, the shutdown circuit is probably activated by the over current
condition on the power lines in the A50 DC-DC Convereter or the A2 P ost Regulator . In this
condition, though the A50 power supplies , +5 VD , +18 V , +7.8 V , -7.8 V , and -18 V are shut
down, the F an P ower +24 V is still supplied to the fan. When the fan is not rotating, the
shutdown circuit is probably activated by the F AN LOCK signal missing.
F or more information about the A50 shutdown circuit operation, see the Figure 5-11 P ower
Supply Block Diagram 1.
Note
Once the A50 shutdown circuit is activated, the only way to reset the circuit is
turning the analyzer power o. W ait a minute after turning the analyzer o.
Then turn it on.
P ower Supply T roubleshooting 5-3