Phasetronics
Page 30
Chapter 8 - Troubleshooting
8.1-SCR Testing Procedure
Remove all power sources from the unit! Disconnect load and line leads. Observe
all lock out / tag out practices.
Equipment required:
•
Digital Volt / Ohm meter
8.1.1 First procedure
Remove line power from the unit and lock out. Disconnect the load and line leads. Note the type of
color coding of the wires going to the firing boards. Phasetronics uses two possible configurations.
The first configuration consists of 4 wires color coded black, yellow, grey and white. The second
configuration consists of 4 wires color coded red, white, red, white. The testing procedure for SCRs is
comprised of two separate tests.
The first procedure tests the anode to cathode integrity of the SCR by performing the following ohm
checks:
+ Lead
- Lead
Good
Consult Factory
L1 Lug
T1 Lug
Greater than 10k ohm
Less than 10k ohm
L2 Lug
T2 Lug
Greater than 10k ohm
Less than 10k ohm
L3 Lug
T3 Lug
Greater than 10k ohm
Less than 10k ohm
8.1.2 Second procedure
The second procedure tests the Gate to Cathode integrity of each SCR. Ohm each Black & Yellow pair of
wires, then ohm each Gray and White pair of wires. Compare your readings to the information in Fig 10
below. For units with six sets of Red/White wires, ohm each set of Red/White wires and compare your
readings to Fig 10 below.
For wire that is color coded black, yellow, gray and white
+ Lead
- Lead
Good
Bad
Black
Yellow
Between 5 and 32 ohm
Less than 5 or greater than 32 ohm
Gray
White
Between 5 and 32 ohm
Less than 5 or greater than 32 ohm
For wire that is color coded red, white, red and white
+ Lead
- Lead
Good
Bad
Red
White
Between 5 and 32 ohm
Less than 5 or greater than 32 ohm
Red
White
Between 5 and 32 ohm
Less than 5 or greater than 32 ohm
Figure 10
Note:
If any of the above readings are out of specification, replace the faulty SCR.
