Specifications

SECTION 5 MACHINE TESTING / TROUBLESHOOTING / SERVICE

Buss cap warning

Serious Shock Possible

The “buss capacitors” in the PC650 will maintain a voltage

charge for approximately 2 minutes after power is removed

from the input of the machine.

The arcing caused by discharging a capacitor into a short-circuit

can cause injury and component damage

To eliminate the voltage from the capacitor, connect the “bleed-

er resistor” across the poles of a charged capacitor and the

stored energy will discharge harmlessly through the resistor.

The approximate discharge time is 30 seconds.

When discharged, the cap can be partially tested by using a multimeter set to

the ohms scale. When checking a capacitor…Connect the + meter lead to the +

pole of the capacitor, and the – lead to the – pole. The meter display will show

a number that will change while the leads are connected, if the meter leads are

reversed, the display will change polarity and the value will change in the oppo-

site direction from the rst test, if the capacitor is good.

Capacitor Information

Serious Shock Possible!

CAUTION

BLEEDER RESISTOR

6” Min. 16AWG

600 V Insulation

5.3 Buss Supply

208 / 230 Volt

The buss supply of the 208 / 230 Volt PC 650 consists of 2 paralleled, 1000μF, 450Vdc capacitors (C1 & C2) that

charge up to the rectied DC voltage output from the input bridge (IBR). This stored voltage is input to the high-

speed switching transistors (IGBTs) and inverted to form high frequency, square-wave AC that is then input to the

main transformer (T1).

Across C1 & C2 are 4, 50kΩ/12W resistors and a 1μF, 630Vdc capacitor. The capacitor, C3 and the resistors reduce

electrical noise, plus the resistors provide a discharge path for the buss caps during “o” conditions.

460 Volt

The buss supply consists of 2 1000μF, 400Vdc capacitors (C1 & C2), connected in series that charge up to the

rectied DC voltage output from the input bridge (IBR). This stored voltage is input to the high-speed switching

transistors (IGBTs) and inverted to form high frequency, square-wave AC that is input to the main transformer (T1).

Across each of the series caps is an RC network, which is comprised of a 10kΩ resistor in parallel with a 1μF capaci-

tor. This network is used for noise reduction, plus the resistors provide a discharge path for the buss caps during

“o” conditions.

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