OSMAC RDR: TRIAC Board Keeps Blowing 4-AMP Fuse
LESSON SUMMARY: This lesson is designed to assist the user in troubleshooting what would cause the 4-AMP fuse on a TRIAC Board to continuously blow.
Special Tools Needed: Digital Multimeter, Flathead Screwdriver
⚠ CAUTION: THIS LESSON MAY INCLUDE INSTRUCTIONS TO TEST HAZARDOUS VOLTAGES (120V-240V) THAT CAN CAUSE SERIOUS INJURY OR DEATH. IT IS RECOMMENDED THAT A LICENSED ELECTRICIAN BE CONTRACTED TO PERFORM SUCH TESTS.
🛑 STOP: ALWAYS TURN OFF THE POWER TO THE SATELLITE BEFORE REMOVING OR INSTALLING COMPONENTS.
If the 4-AMP fuse on a TRIAC Board for OSMAC RDR® repeatedly blows during normal operation, there could be an issue with the TRIAC Board, one or more solenoids in the field, or the Switch & Surge Board. To determine which components require replacement, follow the guided steps below.
Testing the 4-AMP Fuse:
The 4-AMP Fuse on a TRIAC Board for OSMAC RDR® is located directly next to the ribbon cable and screw terminal block. To test the fuse, proceed with the following steps:
*Note: Visually inspecting a fuse is never a trustworthy method to determine the failure or functionality of the fuse.
Start by powering off the satellite.
Remove the fuse from its holders on the TRIAC Board.
Use a digital multimeter on the resistance setting or continuity setting with an audible beep. If using the resistance setting, touch the two multimeter probes together and note the reading on the display; it should be 0 or very close to 0. *Note: Different multimeters will vary slightly.
Proceed to place one probe on each end of the fuse.
If using a digital multimeter on the resistance setting, a working fuse will display a reading close to the reading that was displayed when the two probes were touched together: 0 or very close to 0.
If using a digital multimeter on the continuity setting, a working fuse will create an audible beep.
If the digital multimeter reads Over Limit “OL” on the resistance setting, or no audible beep is heard on the continuity setting, the fuse is damaged and should be replaced.
Replacement 4-AMP Fuses for TRIAC Boards can be purchased here.
Testing Solenoid Resistence:
After replacing the 4-AMP Fuse with a new or known-working fuse, proceed to measure the resistance of each solenoid connected to the TRIAC Board to ensure that there is not a short in one or multiple solenoids. A shorted solenoid will cause the 4-AMP fuse on a TRIAC Board to blow when the system activates the station the solenoid is connected to.
After replacing the 4-AMP Fuse, do not power the satellite back on until the resistance of the corresponding solenoids has been measured and shorted or damaged solenoids have been replaced. To test the solenoids, proceed with the following steps:
Start by making sure power to the satellite is off and proceed to isolate the solenoid(s).
To isolate the solenoid(s), unscrew the station wires from the connector in the satellite. Station wires are screwed into a screw terminal on a Switch & Surge Board or TRIAC Board. The location where your station wires are screwed into (Switch & Surge Board or TRIAC Board) will depend on your individual satellite configuration.
Testing a solenoid can be done at the satellite using the station wires as a test point.
*Note: If you have two or more solenoids wired together and a short is found on the set, and if the wires are spliced together in the field, you will need to dig up the solenoids in order to disconnect and test them individually .
Using a digital multimeter set to the Ohm setting, measure the resistance of the solenoids.
*Note: If the multimeter has a range of settings to chose from, such as 200 Ohms, 2000 Ohms, or 20K Ohms, 200 Ohms should always be used. Do not use the audible continuity function on the multimeter for testing solenoids.
Proceed to place one probe of the multimeter on the Valve Common wire and place the other probe of the multimeter on the station wire.
See the graphic below for an acceptable resistance range based upon your individual configuration:
In-depth instructions on how to check solenoid resistance can be found here.
*Note: If a SuperParts™ TRIAC Board for OSMAC® RDR is installed and a Switch & Surge board is NOT installed in the satellite, the solenoids can be isolated by unplugging the J2 connector on the SuperParts™ TRIAC Board for OSMAC® RDR.
If the resistance measured for a solenoid is outside of the acceptable range, the solenoid is damaged and should be replaced.
After replacing the damaged solenoid(s) proceed to reconnect all station wires to the Switch & Surge Board or TRIAC Board.
Power the satellite on.
If the 4-AMP Fuse no longer blows, the issue has been resolved.
If the 4-AMP Fuse blows upon powering on the satellite, and the satellite has Switch & Surge Boards installed, the Switch & Surge board connected to the TRIAC Board that is blowing the 4-AMP Fuse needs to be tested.
Instructions on how to test the Switch & Surge Board can be found here.
If the solenoids are within the proper resistance range, the Switch & Surge board has been tested and is known to be working properly, and the TRIAC Board still continues blowing the 4-AMP Fuse, the TRIAC Board is damaged and should be replaced.
Replacement TRIAC Boards can be purchased here.
Lesson tags: toro, osmac rdr, toro osmac rdr, osmac rdr repair, osmac rdr help, osmac rdr troubleshooting, osmac rdr exchange, osmac rdr motherboard, osmac rdr triac board, triac board, solenoid resistance, boardtronics
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