Amada Miyachi Unitek STA-100A, Operation Manual, Page: 75 / 154

CHAPTER 5: MAINTENANCE
STA SERIES AC CONTROLS
990-351 5-11
Optional Key Lock
1 To replace the key lock, disconnect the two-wire cable from connector J3 of the Control Panel
Assembly.
2 Unscrew the nut on the rear of the switch.
3 Install a new key lock (or re-install the old one if it is being used) by sliding it into the double
“D” hole in the Control and securing from inside with the nut that comes with the switch.
4 Reconnect the two-wire cable to connector J3 of the Control Panel Assembly.
Optional SCR Assembly, 600,1200, 1800, and 2200 Amp
NOTE: The only difference in the removal/replacement instructions for the 600A and 1200A SCR
assemblies is the attaching hardware. The 600A requires two 10-32 x 1.5 Phillips pan head mounting
screws and #10 internal tooth washers; the 1200A and 1800A SCRs each require four 10-32 x 1.0
Phillips pan head mounting screws and #10 internal tooth washers.
1 Turn the water supply to the cooling water hoses going to the SCR assembly OFF.
NOTE: Place a container beneath the Control to catch water draining from the SCR assembly
and the cooling water hoses.
2 Disconnect the cooling water hoses from the SCR assembly on the bottom of the Control.
Allow all of the water to drain from the SCR assembly.
CAUTION : In the following steps, be careful not to damage the wires attached to the L1
terminal.
3 Remove the bolts, lock washers and flat washers securing L1 bus bar to the SCRs (or SCR and
insulator), and remove L1.
4 Disconnect the cable connector from the SCR Drive Board connector J2.
5 Remove the screws and lock washers attaching the assembly to the Control.
6 Install or re-install the SCR by attaching it to the Control with the screws and lock washers.
7 Reconnect the cable connector to the SCR Drive Board connector J2.
8 Reinstall L1 to the SCRs (or SCR and insulator) with the bolts lock washers and flat washers
removed in step 3.
9 Reconnect the cooling water hoses to the SCR assembly on the bottom of the Control.
10 Turn on the water supply to the cooling hoses going to the SCR assembly. Check for leaks.