Agilent Technologies AGILENT MODELS 6023A and 6028A service manual A2J7-26 A2J7-25, Board

Table 3-2. No-Output Failures

(Bias supplies and AC turn-on circuit functioning)

Status of PFET on/off-Pulses

PWM-ON	PWM-OFF	DEFECTIVE	CHECK FUNCTIONAL CIRCUITS
A2J7-26	A2J7-25	BOARD
lo	lo	A2	Control ckts: CV & CC thru on- & off-Pulse Oneshots *
lo	hi	A2 & A4	PWM and DC-to-DC Converter: A4Q3 and A4Q4 probably failed
hi	lo	A2 & A4	PWM and DC-to-DC Converter: A4Q3 and A4Q4 probably failed
hi	hi	A2 & A4	PWM and DC-to-DC Converter: A4Q3 and A4Q4 probably failed
lo	N	A2	A2U17B,on-Pulse Oneshot and A2Q6A
N	lo	A2 & A4	Off-Pulse Oneshot and DC-to-DC: A4Q3 and A4Q4 probably failed
hi	N	A2 & A4	A2U17A, on-Pulse Oneshot & DC-to-DC: A4Q3, and A4Q4 probably
			failed
N	hi	A2 & A4	off-Pulse Oneshot and DC-to-DC: A4Q3 and A4Q4 probably failed
N	N	A2 & A4	Power-Limit Comparator and DC-to-DC: A4Q3 and A4Q4 probably
			failed
lo= TTL low	hi= TTL high	N = normal 20KHz pulse train, TTL levels

*Decide which to troubleshoot -- the CV Circuit, the CC Circuit, or the PWM and Off-Pulse & On-Pulse Oneshots -- by measuring the CV CONTROL (A2CR24, cathode) and the CC CONTROL (A2CR19 cathode) voltages. Troubleshoot whichever is negative, and if neither is negative, troubleshoot the PWM. Make these voltage measurements after you have implemented the Main Troubleshooting Setup.

Table 3-3. Front-Panel Board Tests

.

Pin	Signal Name	Measureme	Description	Source
No		nt
1	+7.5V	7.5V	Derived from + 15V bias.	A3VR2, A3R3
2	-1V	-1.0V	Derived from –15V bias.	A3R86, A3R85, A3C17
*3	CV VOLTAGE	0-5V	For 0 to full scale output voltage.	A3U2-2, A3R1, A3R87.
*4	CC VOLTAGE	0-5V	For 0 to full scale output current.	A3U3A-1, A3R67
5	VOLTS test	-1888 on	Jumper to + 5V on A3 board.	A3U4-37
		volts display
6	AMPS test	-1888 on	Jumper to + 5V on A3 board.	A3U5-37
		amps display
*7	VOLTS input	0-1V	For 0 to full scale output voltage.	A3R8,A3U7-2,3,10
8	VOLTS low range	TTL high	If VOLTS display is below 20 volts	A3U9C-13, A3U6B
			(press DISPLAY SETTINGS).
9	DISPLAY	TTL high	If DISPLAY SETTINGS switch on	A3S1,A3R80
	SETTINGS		front-panel is depressed.
10	DISPLAY OVP	TTL high	If DISPLAY OVP switch on front-	A3S2,A3R82, A3U6C-8
			panel is depressed.
*11	AMPS input	0-150mV	For 0 to full scale output current.	A3R65,A3R66,A3R67
12	-5 V	-5.0V	Derived from -15 V bias.	A3VR1, A3R2
13	buffered OVP	0-2.2V	1/10 of OVP voltage setting when	A3U3B-6,A3CR5,A3R72
			DISPLAY OVP switch is
			depressed. Varies with OVP
			ADJUST pot.

* Switch A1S4 should be in the NORM position for these tests.

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