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54
NODE (+)
NODE (-)
MEASUREMENT
SOURCE
A2J3-26(PWM-ON)
VM
waveform #1
A2Ul7-6,A2P1-7, A4P1-24,C
A2J3-25(PWM-OFF)
VM
waveform #2
A2U13-5,A2P1-13,A4P1-26,A
A4Q3-D
A4Q4-S
39Vdc
A1C4 ( + ),A4P1-10,A,C
A1C4 ( - ),A4P1-4,A,C
Outputs:
NODE (+)
NODE (-)
MEASUREMENT
A4Q3-G
A4Q3-S
waveform #3
A4Q4-G
A4Q4-S
waveform #3
A4Q3-D
A4Q3-S
waveform #4
A4Q4-D
A4Q4-S
waveform #4
A2J3-18
A2J3-4
waveform #5
Note:
The Gate (G) and Source (S) leads of PFETs A4Q3 and A4Q4 can be accessed from the circuit side of the
board and used as test points. The Drain (D) of A4Q3 can be picked up at its case or from the cathode of
A4CR13. The Drain of A4Q4 can be picked up at its case or from the anode of A4CR14.
If all the INPUT measurements are correct but the OUTPUT Vgs waveform (3) is incorrect, the problem may be caused by
weak PFETs. Two 6800pF capacitors (HP PN 0160-0159) can be substituted for the PFETs (G to S) to check waveform 3.
If the waveform is still incorrect, the problem may be located in the drive components. If you replace the PFETs, replace
both the PFETs and associated drive components as furnished in PFET Service Kit. HP Part No. 5060-2860.
The PFETs are static sensitive and can be destroyed by relatively low levels of electrostatic voltage.
Handle the A4 power mesh board and the PFETs only after you, your work surface and your equipment
are properly grounded with appropriate resistive grounding straps. Avoid touching the PFET’s gate and
source pins.
Troubleshooting Bias Supplies
+5V On A2 Control Board. The PWM A2U6 includes a clock generator (45KHz set by A2R53 and A2C26), and a
current limit (2Adc set by 0.15Vdc across A2R50). It turns off each output pulse using the difference between the voltage
at voltage divider A2R46-A2R47 and the 2.5Vdc set by voltage regulator A2U5.
Circuit Included. +5Vdc bias supply circuitry from connector pins A2P1-15 through jumper A2W3 on A2 control board.
Setup. The Main Troubleshooting Setup, Page 48. Apply the ac mains voltage to the bias transformer, and set the external
supply to 0Vdc.
Input:
NODE
MEASUREMENT
SOURCE
A2J3-22
≈
20Vdc
A1CR6,A1CR7
Outputs:
NODE
MEASUREMENT
A2U6-6
≈
2 to 4Vdc sawtooth, 45KHz
A2U6-12,13
≈
19V pk, 15
µ
s pulses, 45KHz
Summary of Contents for 6038A
Page 4: ......
Page 8: ......
Page 34: ...34 Figure 3 1 Troubleshooting Isolation ...
Page 35: ...35 Figure 3 1 Troubleshooting Isolation continued ...
Page 37: ...37 Figure 3 3 Clock and Primary SA Waveforms ...
Page 40: ...40 Figure 3 4 Readback and Secondary SA Waveforms ...
Page 56: ...56 Figure 3 7 Waveforms ...
Page 62: ...62 Figure 4 1 HP IB Block Diagram ...
Page 65: ...65 Figure 4 2 Front Panel Block Diagram ...
Page 90: ......
Page 93: ...93 Figure 6 1 Top View Top Covers Removed ...
Page 94: ...94 Figure 6 2 Main Board A1 Component Location ...
Page 95: ...95 Figure 6 3 Control Board A2 Component Location ...
Page 96: ...96 Figure 6 4 Front Panel Board A3 Component Location ...
Page 97: ...97 Figure 6 5 Power Mesh Board A4 Component Location ...
Page 98: ...98 Figure 6 6 HP IB Board A8 Component Location ...
Page 105: ...105 Figure 3 1 Troubleshooting Isolation option 001 ...
Page 106: ......