Agilent Technologies 6683A CV/CC Status Annunciators Troubleshooting, Static Troubleshooting

CV/CC Status Annunciators Troubleshooting

When troubleshooting the CV/CC status annunciators or status readback circuits, first measure the voltage drop across the gating diodes, which are Al0D651 for the CC circuit and Al0D652 for the CV circuit (see A10, Sheet 2). A conducting diode indicates an active (ON) control circuit. This forward drop is applied to the input of the associated status comparator (A10U502) and drives the output low. The low signal indicates an active status which is sent to the secondary microprocessor A10U506 via Programmed GAL Al0U505 (see schematic Sheet 1). The front panel CV annunciator lights when the CV mode is active (CV is low) and the CC annunciator lights when the CC mode is active (CC is low). If neither is active, the UNREGULATED (Unr) annunciator comes on.

A3 FET Board Troubleshooting

Because test points on the FET board are not accessible when the board is installed, troubleshooting must be performed with the board removed from the power supply. Both static (power removed) and dynamic (power applied) troubleshooting procedures are provided. The location of different test points are shown by encircled numbers on the A3 FET Board schematic and component location diagrams (see Chapter 6). There are two isolated FET bridge assemblies (see schematic in Fig. 6-10 sheets 1 and 2). Test each FET bridge individually.

Note		If any power FET (Q201-204, Q301-304, Q211, Q311, Q222, Q322, Q233, Q333, Q244, Q344) is
		defective, you must replace all eight with a matched set.
		Table 3-4. FET Troubleshooting Chart
		Procedure	Result
		Static Troubleshooting
1.	Turn the power supply off and remove the A3 FET board with its heatsink assembly
	attached (see "Disassembly Procedures").
2.	Measure the resistance between the + Rail (E202 & E302) and the - Rail ( E201 &		≥ 20MΩ.
	E301).
3.	Measure the resistance between the gate of each FET		>15KΩ.

(Q201-204, Q211, Q222, Q233, Q244, and Q301-304, Q311, Q322, Q333, and Q344) and common (-Rail).

4.Measure the resistance across capacitor C201 & C301.

5.Measure the resistance across the 15V bias input (E206 to E207 and E306 to E307).

≈150Ω.

≈1KΩ in the forward direction and 490Ω in the reverse direction.

Continue with Dynamic Troubleshooting on the next page

Troubleshooting 53