Tech Note 562 Detail

Voltage from ground to the 0V terminal is 500VDC.

Affected Products:

SF-9585a High Voltage Power Supply

Problem/Symptom:
Voltage from ground to the 0V terminal is 500VDC. Voltage from ground to the -50V terminal is 550VDC.

PASCO Solution:

The SF-9585A has three DC output terminals -50V, 0V and +500V. The 0V terminal is not connected to ground, but is a floating voltage. If the voltage on the defective supplies is measured from ground to the 0V terminal, the voltage is 500VDC. If the voltage from ground to the -50V terminal is measured, the voltage is 550VDC. The voltage between ground and the 500V terminal is very small, or zero. Therefore, if one touches the 0 or -50V terminal and ground, there will be a voltage of 500VDC or 550VDC, respectively with a current of up to 50 mA, which can be hazardous.

The cause of the defect is a defective through-plating of the holes in the circuit board through which the terminal connectors pass.

We ask that you perform the following identification procedure to determine if your power supply is defective:

  1. Disconnect the unit from any power source.
  2. Using an ohmmeter, check the resistance between the yellow/green ground terminal on the rear panel of the unit and the +500V terminal on the front of the unit.
  3. If the resistance is greater than 1 M© (typically 5M©) the unit does not have the defect.
  4. If the resistance is less than 10© (typically 0.3©) the unit is defective and must be returned to Pasco for modification.

If you determine that your unit is defective, please contact Pasco Technical Support (1-800-772-8700 x 78) to arrange the return of your unit(s).

Creation Date: 03/13/2006
Last Modified: 10/27/2009
Mod Summary: