Specifications
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5.3.2 Buss Supply Values
5.3.3 Buss Supply Testing
SECTION 5 MACHINE TESTING / TROUBLESHOOTING / SERVICE
Buss Supply Values & Testing
208 / 230 Volt Model
The buss supply for the 208/230 Volt model of the PC650 consists of 3 capacitors and 4 resistors. R2, R15, R16 & R17
are all 50kΩ12Wresistors. The resistors are used for providing a discharge path for the buss supply. C3, a 1μF /
630Vdc capacitor, is used primarily for ltering.
The key components in the buss are the polarized capacitors, C1 & C2. These two caps are both 1000μF
/ 450Vdc capacitors. The buss can be measured across either cap because they are connected in paral
-
lel. To measure this buss, connect the positive (red) lead of a voltmeter to “+” post of either buss cap and
the negative (black) lead to the “-“ of the same cap. The nominal buss voltage value is 325Vdc. However,
since the tolerance of the input voltage is +/- 15%, the range of acceptable voltage buss readings is 277
– 375Vdc.
--WARNING---Buss caps can maintain a charge for some time after input power has been removed from the system.
It is imperative that these caps be discharged before testing. It is recommended that a bleeder resistor be used to
discharge the buss caps. The specications of which should be approximately a 20kΩ, 20W resistor with high volt-
age insulation on its leads.
--See beginning of section 5.3 for details--
460 Volt Model
The 460 Volt model of the PC650 consists of 4 caps and 2 resistors. Capacitors C15 & C3 (1μF, 630Vdc) are used for
ltering and resistors R15 & R2 (10kΩ, 20W) are used for providing a discharge path.
C1 & C2 (1000μF, 400Vdc) are the main buss components and because C1 & C2 are connected in series in the 460 Volt
model, the buss voltage is divided in half, with ½ of the buss voltage being across C1 and the other ½ being across
C2. To measure the total voltage, place the positive (red) lead on the “+” of the C1 and the negative (black) lead on
the “-“ of C2.
Ideally, the buss should read 650Vdc with 325Vdc being across C1 and 325Vdc being across C2. Due to the +/- 15%
tolerance of the input would yield a total buss voltage (across C1 & C2) of 553 – 748Vdc.
It is recommended to use a bleeder resistor to discharge the buss caps.
Testing Buss Capacitors
The buss capacitors can be easily tested to insure that they are good. It is recommended that a capacitance meter
be used to measure the capacitance, however, a good indication of a good cap can be determined by conducting
an ohms test.
With the machine powered down and caps fully discharged, place the red lead of a voltmeter, in the ohms scale, on
the “+” post of the buss cap and the black lead on the other post of the same cap. The resistance reading should be
in the MΩ range and should be increasing. Reverse the leads and the resistance reading should remain in the MΩ
range, however, the value should be decreasing.
Again, this is only a “good indication” that the capacitor is good. It is still recommended that the capaci-
tance be checked with a capacitance meter.
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