Bird Technologies 8578B150 Series - Manual (Page 27)

Maintenance
15
Diagnosing the RF Assembly
Note:
The RF section for the Model 8578A100 and 8578B100 is
comprised of a parallel combination of 9 resistors resulting in a total
nominal resistance of 55 ohms.
The RF section for Model 8578A150 and 8578B150 is comprised of a
parallel combination of 12 resistors resulting in a total nominal resis-
tance of 60 ohms.
If there has been a drastic change in the resistance of the load or if you
have reason to suspect a resistor has failed, the following procedure
may be helpful in finding a faulty resistor.
1. Perform a visual inspection for cracks or burned spots on the surface of
each resistor.
Note:
If no visual discrepancies are found to indicate resistor fail-
ure, it will be necessary to take resistance measurements on each resis-
tor individually.
2. Remove the resistors from the load.
Note:
The resistors are held very firmly in their clips. Use caution
and carefully remove one end of the resistors at a time.
3. Connect the test leads across each resistor end using a digital multimeter
or an ohmmeter with an accuracy of 1% at 50 ohms.
•
For Models 8758A100 and 8578B100, individual resistance
measurements at 25°C (77°F) should be 500 ohms ± 20%.
•
For Models 8578A150 and 8578B150, individual resistance
measurements at 25°C (77°F) should be 720 ohms ± 20%.
4. Record the value of the resistance for each resistor.
Note:
If resistors are found that greatly exceed the respective
ranges, they should be replaced. Contact Bird Technologies Group for
replacement resistors. Contact Bird Technologies Group customer ser-
vice for replacement resistors (866) 695-4569.
Replacing the Resistors
Note:
To reassemble the RF assembly and panel, reverse the disas-
sembly instructions given above. Ensure to install all of the screws in
the panels.
Replacing the Blower Assembly
Motor Blower Assembly Replacement, 8578A Series
1. Remove and retain the 22 Phillips head machine screws from the edges of
the right side panel.
2. Remove the panel.
3. Remove, carefully, the resistors behind the right side panel.
CAUTION
Do not use excessive force, as there is the possibility of the resistors chipping
or cracking
WARNING
Disconnect from RF power sources and the AC line before any disassembly
or service. Otherwise, there is a potential for electrical shock.