HP 6033A series Service Manual page 52

SYMPTOMS
unexplained OVP shutdowns
no current limit
max current < 10Adc (6038A)
< 30Adc (6033A)
max power < specified
max voltage < 60Vdc (6038A)
< 20Vdc (6033A)
cycles on & off randomly
CV overshoots
output noise (<1KHz)
output noise (>1KHz)
CV regulation, transient
response, programming time
CC regulation
CV oscillates with capacitive
loads
CC oscillates with inductive
loads
Status of FET On/Off-Pulses
PWM-ON PWM-OFF
A2J3-26 A2J3-25
Lo Lo
Lo Hi
Hi Lo
Hi Hi
Lo N
N Lo
Hi N
N Hi
N N
Lo= TTL low Hi= TTL high
* 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.
52
Table 3-10. Performance Failure Symptoms
DEFECTIVE
BOARD
A2
A2
A2
A2, A1
A2, A1
A2, A1
A2
A2,A1
A1, A4
A2, A1
A2
A2
A2
Table 3-11. No-Output Failures
(Bias supplies and AC turn-on circuit functioning)
DEFECTIVE
BOARD
A2 Control ckts: CV & CC thru On- & Off-Pulse Oneshots *
A2&A4 PWM and DC-to-DC Converter: A4Q3 and A4Q4 probably failed
A2&A4 PWM and DC-to-DC Converter: A4Q3 and A4Q4 probably failed
A2&A4 PWM and DC-to-DC Converter: A4Q3 and A4Q4 probably failed
A2 A2U17B, On-Pulse Oneshot and A2Q6A
A2&A4 Off-Pulse Oneshot and DC-to-DC: A4Q3 and A4Q4 probably failed
A2&A4 A2U17B, On-Pulse Oneshot & DC-to-DC: A4Q3 and A4Q4 probably
failed
A2&A4 Off-Pulse Oneshot and DC-to-DC: A4Q3 and A4Q4 probably failed
A2&A4 Power-Limit Comparator and DC-to-DC: A4Q3 and A4Q4 probably
failed
N= normal 20KHz pulse train, TTL levels
CHECK FUNCTIONAL CIRCUITS
OVP circuit, CV circuit
CC circuit
CC Clamp, CC circuit
Power Limit, 20KHz clock, transformer AlT1
CV Circuit, diodes A1CR1-CR4
AC-Surge-&-Dropout Detector, Mains Voltage
Select switch A1S2
A2U10A, A2CR20, A2R94
CV circuit, input filter
transformer AlT1, Output Filter, snubbers
A4R7/R8/C5/CR5/, A4R13/
R14/C6/CR6, A4R33/C13
wrong sensing
low ac mains voltage, CV circuit
low ac mains voltage, CC circuit
A2R10, A2C51, A2R95, A2R96, A2R86,
A2C47, A2R71, A2C36
A2U10, A2R86, A2C47, A2C43, A2R77, A2U3D
A2U3D, A2R30, A2C44, A2R76, A2R75,
A2C42, A2C41, A2R1
CHECK FUNCTIONAL CIRCUITS