28F-28, Frequency Counter Method | Lincoln Electric SVM153-A

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F-28F-28

TROUBLESHOOTING & REPAIR

ENGINE THROTTLE ADJUSTMENT TEST (CONTINUED)

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6.If either of the readings is incorrect, adjust the throttle as follows:

Adjust HIGH IDLE: Use the 10mm wrench to loosen the locking nut. See Figure F.8 for location of the adjusting screw and lock- ing nut. Turn the threaded screw counter- clockwise to increase the HIGH IDLE speed. Adjust the speed until the tach reads between 1890 and 1910 RPM. Retighten the locking nut.

Adjust LOW IDLE: First make sure there is no load on the machine. Set the IDLE switch to AUTO and wait for the engine to change to low idle speed. Use the 10mm wrench to loosen the solenoid lever arm locking nut. See Figure F.9. Adjust the col- lar, to change the amount of throw in the lever arm, until the tach reads between 1450 and 1500 RPM. Retighten the locking nut.

Frequency Counter Method

1.Plug the frequency counter into one of the 115 VAC auxiliary receptacles.

2.Start the engine and check the frequency counter. At HIGH IDLE (1900 RPM), the counter should read 63 Hz. At LOW IDLE (1475 RPM), the counter should read 49 Hz. Note that these are median measure- ments; hertz readings may vary slightly above or below.

3.If either of the readings is incorrect, adjust the throttle as follows:

Adjust HIGH IDLE: Use the 10mm wrench to loosen the locking nut. See Figure F.8 for location of the adjusting screw and lock- ing nut. Turn the threaded screw counter- clockwise to increase the HIGH IDLE speed. Adjust the speed until the frequen- cy reads 63 Hz. Retighten the locking nut.

Oscilloscope Method

1.Connect the oscilloscope to the 115 VAC receptacle, according to the manufacturer’s instructions. At HIGH IDLE (1900 RPM), the waveform should exhibit a period of

15.8milliseconds. At LOW IDLE (1475 RPM), the waveform should exhibit a period of 20.3 milliseconds. Refer to the NORMAL OPEN CIRCUIT VOLTAGE WAVEFORM (115 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:

15.8milliseconds. Retighten the locking

nut.

Adjust LOW IDLE: First make sure there is no load on the machine. Set the IDLE switch to AUTO and wait for the engine to change to low idle speed. Use the 10mm wrench to loosen the solenoid lever arm locking nut. See Figure F.9 Adjust the col- lar, to change the amount of throw in the lever arm, until the period is 20.3 millisec- onds. Retighten the locking nut.