| The term SCR stands for Silicon Controlled | | | | guess, or a hit-and-miss operation. |
| Rectifier. These three terminal devices can be | | | | Failure analysis or Functional Test of the SCR |
| tested by a number of different methods. The | | | | should always be performed when the device is |
| more common methods utilize a DVM (Digital Volt | | | | out of circuit. This means that the component |
| Meter) or an Analog Meter. Usually the SCR is | | | | should not be electrically connected to anything |
| tested by simply looking for the lack of | | | | other than the Test Equipment that is used to |
| conduction between Anode and Cathode leads. A | | | | evaluate the devices functionality. |
| high resistance would indicate a functional device, | | | | At a well equipped Repair Center, SCR's are |
| given the limitations of not gating the device. | | | | tested utilizing an SCR Component Analyzer. This |
| Another method that is used in some Repair | | | | equipment confirms the SCR's functionality, by |
| Centers involves a Test lamp, a battery and a | | | | gating the device and intelligently measuring its |
| few Test leads. The lamp and battery are | | | | device characteristics. Confirm that the device |
| connected in Series then placed across the SCR's | | | | tests as follows: |
| Anode and Cathode leads (the negative lead of | | | | Press the Red Test Button to turn the |
| the battery connects to the SCR's Cathode lead). | | | | Component Analyzer on. The Blue Result LED will |
| A flying test lead is then used to trigger the SCR | | | | light. Attach the Test Leads to the SCR's Gate, |
| by momentarily connecting the positive terminal | | | | Cathode and Anode Terminals. It is not important |
| of the battery to the SCR's gate lead. | | | | which leads go where. The Component Analyzer |
| Both of these Test methods can provide an | | | | will determine the connection details. |
| indication of device functionality when no other | | | | Press the Red Test Button. The first three LED's |
| methods are available. Unfortunately, both | | | | will display the connection details for a functional |
| methods require the Technician to consult a | | | | device. The Result LED will display the Test result. |
| Datasheet or Service Manual prior to Testing the | | | | A Blue LED means that the device has an open |
| SCR. This ensures correct lead configuration. If | | | | circuit condition. A Red LED means that the |
| the device pinout can not be determined, then the | | | | device is shorted. A Green LED means that the |
| whole Test process becomes little more than a | | | | device is Functional. |