Lincoln Electric SVM188-A service manual Replacement Procedure

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F-43 TROUBLESHOOTING AND REPAIR F-43

SCR RECTIFIER BRIDGE

REMOVAL AND REPLACEMENT PROCEDURE (cont.)

FIGURE F.18 – RECTIFIER REPLACEMENT

Thread Forming Screw Plain Washer 5/16-18 Hex Nut Negative Output Lead Choke Lead

	Insulator	Lock Washer	Plain Washer	Output Snubber Lead
				Lock Washer
	Bridge Mounting	Transformer	‘A’ Lead from
		Secondary Lead
	Bracket		Snubber	3/8-16 Hex Nut
Rectifer Mounting	Insulator
	Insulator		Heat Sink
Bracket				3/8-16 x 1 Cap Screw

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Fig. 18 ‘A’		Fig. 18 ‘B’
		OUTPUT	A
		SNUBBER
A	SECONDARY	CONNECTION	A	A
	LEAD CONNECTION	A		A
		A
	(6 PLACES)
	MOUNTING
	BOLTS (4)
		A		A
		A
	A			A
215
210	A
A
OUTPUT		A
SHUNT
CONNECTION
STRAP
	A

Plain Washers (2)

Fig 18 ‘C’

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REPLACEMENT PROCEDURE

NOTE: Any instructions packaged with the replace- ment SCR Bridge assembly will supercede these instructions.

1.Use steel wool or Scotch-Brite to provide a bright, clean,smooth paint-free surface for connection of the leads. Clean the surfaces of the heat sink as well as those of the leads. Wipe away any abrasive material with a clean cloth.

2.Apply a thin coating of joint compound (provided with new assembly)to all of the heatsink areas where leads will be connected.

3.Carefully mount the SCR assembly into the DC- 600 using the original hardware or the hardware provided with the new assembly. See Figure F.18’A’.

NOTE: A new rectifier assembly will have mounting brackets with both 1/2” holes and 3/8” holes to allow for proper mounting in all units. The spare insulating tubes and washers are for use in older machines.

4.Reconnect the transformer secondary and snubber ‘A’ leads to the assembly. See Figure F.18’B’.

5.Mount the Output Snubber to the left side bracket and connect the lead to the Choke. See Figure F.18’C’.

NOTE: Torque all bolts for the following minimum settings:

1/4”	bolts	6 ft/lbs.
5/16” bolts		11 ft/lbs.
3/8”	bolts	19	ft/lbs.
1/2”	bolts	45	ft/lbs.

6.Bolt the shunt to the Positive Output Stud connec- tion strap and connect the # 210 and #215 leads as they were on the original assembly.

NOTE: It is important that the current feedback leads(twisted pair) and the meter leads are connected across the shunt and the other 215 leads connected near the top of the shunt assembly. See Figure F.18.

DC-600