Troubleshooting Down Programmer - HP 6033A series Service Manual

-15 V On A2 Control Board. Voltage regulator A2U4 regulates the voltage across resistor A2R32 to be 1.25Vdc.
Circuit Included. -15 Vdc bias supply circuitry from connector pin A2P1-30 through test point A2J3-21 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 (+)
A2U4(IN), A2C16 (-)
Outputs:
NODE ( + )
A2U4 (ADJ)
A2VR2 (cath.)
A2R33, A2R34
To check if load on -15V is shorted, remove jumper A2W3.
Refer to Down Programmer, for the + 8.9Vdc bias supply, and refer to OVP Circuit, for the + 2.5V bias supply.

Troubleshooting Down Programmer

The down programmer loads the output when either MASTER ENABLE is low or CV ERROR is more negative than about
- 6Vdc. Comparator A4U3B triggers down programming when the voltage at A4U3B-5 is less than about 3Vdc. The
collector-emitter current through transistor A4Q6 increases as the output voltage decreases because of feedback from
voltage divider A4R24-A4R27 at A4U3A-2
Circuit Included. Down programmer and 8.9V bias supply on A4 power mesh board.
Setup. The Main Troubleshooting Setup, Page 48, except connect the external supply to the unit's + OUT ( + ) and - OUT
( - ) terminals. Apply the ac mains voltage to the bias transformer. Set the external supply (EXTERNAL) and adjust the
unit's voltage setting (INTERNAL) as instructed below.
Outputs:
NODE
A4U4 (OUT)
A4U3B-7
A4U3B-7
A4U3B-7
A4U3A-2
A4R26
A4Q6 (base)
A4U3A-1
A4R26
MEASUREMENT
≈ - 24Vdc
NODE (-)
A2U24 (OUT)
A2VR2 (anode)
A2VR2 (cath.)
Set Voltage (Vdc)
External Internal
- -
0 2
10 0
0 2
0 2
0 2
20 2
20 2
20 2
SOURCE
A1U1, A1C1(+)
MEASUREMENT
l.25Vdc
11.7Vdc
2.05Vdc
Setup
unplug TS1
reconnect TS1
unplug TS1
Measurement
8.9Vdc
0Vdc
0Vdc
7.8Vdc
0.43Vdc
≈0.41Vdc (6038A)
0.2Vdc (6033A)
1.0Vdc
4.0Vdc
≈0.34Vdc (6038A)
≈0.11Vdc (6033A)
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