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Teledyne API – Technical Manual - Model 300E Family CO Analyzers Troubleshooting & Repair
289
A voltmeter should be used to verify that the DC voltages are correct per the values in the table below, and an
oscilloscope, in AC mode, with band limiting turned on, can be used to evaluate if the supplies are producing
excessive noise (> 100 mV p-p).
Table 13-7: DC Power Supply Acceptable Levels
CHECK RELAY BOARD TEST POINTS
FROM TEST POINT TO TEST POINT
POWER
SUPPLY
ASSY
VOLTAGE
NAME # NAME #
MIN V MAX V
PS1 +5 Dgnd 1 +5 2 4.8 5.25
PS1 +15 Agnd 3 +15 4 13.5 16V
PS1 -15 Agnd 3 -15V 5 -14V -16V
PS1 Agnd Agnd 3 Dgnd 1 -0.05 0.05
PS1 Chassis Dgnd 1 Chassis N/A -0.05 0.05
PS2 +12 +12V Ret 6 +12V 7 11.75 12.5
PS2 Dgnd +12V Ret 6 Dgnd 1 -0.05 0.05
13.5.3. I
2
C BUS
Operation of the I
2
C bus can be verified by observing the behavior of DS6 and DS7 on the motherboard and D1
on the relay board in conjunction with the performance of the front panel display. Assuming that the DC power
supplies are operating properly and the wiring from the motherboard to the keyboard, and the wiring from the
keyboard to the relay board, is intact, the I
2
C bus is operating properly if:
DS6 and DS7 on the motherboard are flashing at least once every 2 seconds and D1 on the relay board is
flashing, or;
D1 is not flashing but pressing a key on the front panel results in a change to the display.
13.5.4. KEYBOARD/DISPLAY INTERFACE
The front panel keyboard, display and Keyboard Display Interface PCA (P/N 03975 or 04258) can be verified by
observing the operation of the display when power is applied to the instrument and when a key is pressed on the
front panel. Assuming that there are no wiring problems and that the DC power supplies are operating properly:
1. The vacuum fluorescent display is good if on power-up a “-“ character is visible on the upper left hand
corner of the display.
2. The CPU Status LED, DS5, is flashing, see Section 13.1.4.1.
3.
If there is a “-“ cha
racter on the display at power-up and D1 on the relay board is flashing then the
keyboard/display interface PCA is bad.
4. If the analyzer starts operation with a normal display but pressing a key on the front panel does not
change the display, then there are three possible problems:
One or more of the keys is bad,
The interrupt signal between the Keyboard Display interface and the motherboard is broken, or
The Keyboard Display Interface PCA is bad.
04288D DCN5752