Lincoln Electric SVM150-A service manual Oscilloscope Method, Vibratach Method

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F-22 F-22

TROUBLESHOOTING & REPAIR

ENGINE THROTTLE ADJUSTMENT TEST (continued)

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Oscilloscope Method

1.Connect the oscilloscope to the 120 VAC receptacle, according to the manufacturer's instructions. At HIGH IDLE (3700 RPM), the waveform should exhibit a period of 16.2 milliseconds. At LOW IDLE (2400 RPM), the waveform should exhibit a peri- od of 25.0 milliseconds. Refer to the NOR-

MAL OPEN CIRCUIT VOLTAGE WAVE- FORM (120 VAC SUPPLY) HIGH IDLE - NO LOAD in this section of the manual.

2.If either of these waveform periods is incor- rect, adjust the throttle as follows:

Adjust HIGH IDLE: Use the 3/8" wrench to loosen the spring-loaded adjustment nut. See Figure F.5 for location of the adjustment nut. Turn the nut clockwise to increase the HIGH IDLE speed. Adjust the speed until the period is 16.2 milliseconds.

Adjust LOW IDLE: First make sure there is no load on the machine. Set the IDLER switch to AUTO and wait for the engine to change to low idle speed. Use the 7/16" wrench to adjust the solenoid nut, which changes the amount of throw in the throttle lever arm. See Figure F.6 for the location of the adjustment nut. Adjust the nut until the period is 25.0 milliseconds.

Vibratach Method

1.Place the vibratach as close to the engine as possible. With the machine case top removed, the top of the air cleaner is the best location.

2.Start the engine and observe the whip han- dle of the vibratach. At HIGH IDLE (3700 RPM), the whip handle should exhibit max- imum oscillation. At LOW IDLE (2400 RPM), the whip handle should exhibit mini- mum oscillation. Note that these are medi- an measurements; vibratach readings may vary slightly above or below.

3.If either of the vibratach indications is incor- rect, adjust the throttle as follows:

Adjust HIGH IDLE: Use the 3/8" wrench to turn the spring-loaded adjustment nut. See Figure F.5 for location of the adjustment nut. Turn the nut clockwise to increase HIGH IDLE speed. Adjust the speed until the vibratach whip han- dle exhibits maximum oscillation at 3650 to 3750 RPM.

Adjust LOW IDLE: First make sure there is no load on the machine. Set the IDLER switch to AUTO and wait for the engine to change to low idle speed. Use the 7/16" wrench to adjust the solenoid nut, which changes the amount of throw in the throttle lever arm. See Figure F.6 for location of the adjustment nut. Adjust the speed until the vibratach whip handle exhibits minimum oscillation at 2350 to 2450 RPM.

When finished testing, perform the Case Cover Replacement procedure.

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