34.1 Low Voltage Power Supply (LVPS) - NGC - Troubleshooting Guide

The Low Voltage Power Supply (LVPS) in the control is responsible for producing the voltage needed to power the Maincon processor,  and other low voltage components on the machine.

The PSUP PCB supplies 160VDC to the LVPS board at J1 [1]. The LVPS converts this to a regulated +5VDC, +12VDC, and -12VDC signals that are returned to the PSUP PCB from J2 [2]. The LVPS has a fuse [3] to protect the device in case of a short circuit on an component using it for power.

The sections below provide possible symptoms with corrective action, and other information that can be used to troubleshoot issues related to the LVPS on both 15inch and 19inch machines.

The LVPS supplies several different components on the machine.

It supplies the Maincon PCB with power, which is the processor that controls the machine. 

The 12VDC supplied by the LVPS also is used to power the SKBIF PCB in the pendent.

If there are power issues related to these components, troubleshoot the other components before the LVPS:

SKBIF Troubleshooting Guide

Maincon PCB Troubleshooting Guide

PSUP PCB Troubleshooting Guide

If troubleshooting an issue where you suspect the maincon isn't receiving power, start by inspecting the maincon. An example of this would be if the machine fails to boot up.

Note: Refer to the Main Processor PCB TSG for both 15inch and 19inch machines for more information on troubleshooting the main processor.

Look for the LED in the upper left region of the Maincon PCB [1]. If the LED's labeled '+5V' is red [1],  then the maincon is receiving power.

If the LED's are lit, check the indicator lights on the PSUP PCB.

Verify that all 3 of the LEDs for +5V, +12V, and -12V are lit as shown in the image [1]. 

If they LED's are lit, then the PSUP is receiving the signals from the LVPS. Even if the LED's are lit, measure the voltages to make sure that the voltages are within the acceptable ranges. Measure at both P20 (output to Maincon) and P19 (input from LVPS).

P20:

• Pin 8 to Pin 7: 4.75 - 5.25VDC
• Pin 5 to Pin 6: 11.5 - 12.5VDC 
• Pin 1 to Pin 6: -11.5 - -12.5VDC

P19:

• Pin 5 to Pin 6: 4.75 - 5.25VDC
• Pin 1 to Pin 3: 11.5 - 12.5VDC 
• Pin 4 to Pin 3: -11.5 - -12.5VDC

If all the measured voltages are in range, then the LVPS is functioning as it should and the LVPS should not be replaced. 

If the measurements on P19 are within range, but the measurements on P20 are not, then the PSUP PCB needs to be troubleshot.

Note: If there is no voltage measured on the output of the LVPS, check if the LVPS is receiving 155-162VDC from the PSUP. If the LVPS isn't receiving any power, check the connections/cables going from the PSUP P21 to the LVPS.