Lincoln Electric V155-S service manual Inverter Board Resistance Test

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F-17		TROUBLESHOOTING & REPAIR	F-17
	INVERTER BOARD RESISTANCE TEST (CONTINUED)
		FIGURE F.7 – INVERTER BOARD TEST POINTS
	Output	Collector	D9
	Terminals	Channel A
	INVERTER BOARD
			Red
			Black

Point 1	D7	D3
(center leg)
R24 = PTC
Point 2	Collector
(solder pad)	Channel B

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7. Check the diodes D3 and D9 for “shorts” or “opens”. See Figure F.7.

8. Check diode D7, but remember, some resistance (approx. 27-28 ohms) will be read in both polarities. This will occur because D7 is a snubber diode and is connected in parallel to the snubber resistors R8, R9 and R10. See wiring diagram X0519. See Figure F.7.

9. Check the five output diodes for “shorts” or “opens”. Check from the center terminal (Point 1) of each Diode (all center terminals of the diodes are com- mon with the heatsink) to the large copperl area “point 2”. See Figure F.7.

Note: Actual voltage readings will vary depending on the meter being used. Similar tests on all devices should give similar results

10.Check the resistance between the thermal protec- tion terminals R24. It should be about 36-40 ohms. See Figure F.7.

11.Check the resistance between output terminal con- nections. It should be about 8.5Kohms.

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INVERTEC® V155-S