14
Baker Instrument Company
The Measure of Quality
2.
See Voltage Busline and Crystal Checkout procedures and correct any voltage
Busline or crystal output and frequency problems.
3.
To determine if the CRT tube is defective a check is needed to ensure that +12VDC is
present on P1 CRT pin 7 and then pins 1 and 10 are grounded.
4.
Check P1 CRT pin 2 with a digital multimeter, this measurement will be adjustable
with the intensity potentiometer, it should range from –14VDC to +5.6VDC, if not
check R9 on the A/D board and its connections.
5.
Check P1 CRT pin 3, this measurement should be approximately –110VDC.
6.
Check P1 CRT pin 4, this measurement will be adjustable with the intensity
potentiometer and will range from –110VDC to +5.6 VDC, if not check R9 on the
A/D board.
7.
Check P1 CRT pin 6 for a 4-volt square waveform pulsing negatively to zero (0)
volts. Repetition rate will be every 30
µ
S and the negative duration will be 4
µ
S. If
signal is not present trace back to U24 pin 4 and then to U1 on the Controller board.
Replace if necessary.
8.
Check P1 CRT pin 9 for a 5-volt positively pulsed waveform. Repetition rate will be
every 17mS and the positive duration should be 500
µ
S. If not present, trace signal
back to U1 on the Controller board. Replace if necessary.
9.
Check P1 CRT pin 8 for 2.4 volt data entering from the Controller board U27 pin 13,
replace if necessary.
10.
If above signals and voltages are correct, replace CRT tube.
N
O
H
IPOT VOLTAGE AT TEST LEADS
1.
Ensure the tester function switch is in the hipot mode at 100
µ
A/Division and that the
test lead select switch is in the Hipot selection.
2.
Measure at T2 pin 2 with a digital multimeter, connect positive lead at this point and
the negative lead to chassis ground. Set the meter to AC volts. This point should be a
line voltage upon turning the on/off switch to the on position.
3.
Measure at T2 pin 3, this point will be variable depending on the position of the
output control knob. At the full counter-clockwise position this voltage will be less
than 3 volts AC. At approximately ½ output turning clockwise this voltage will be ½
line voltage. If not present, check the neutral connection to the variac, if this
connection is present replace T2.
