Specifications

Chapter 4: Troubleshooting

Power Supply Troubleshooting

Figure 4-14 Case fans

3 Apply AC power to the oscilloscope and turn it on if it does not start up automatically.

Visually check to see if any of the fans are not turning. If none of the fans are turning,

it is likely a problem with the high side drive circuitry for the case fans. In that case,

you would replace the backplane assembly.

If any of the fans are turning, then they are probably not the cause of your shutdown

problem. (You should still replace any fans that are not turning, however.)

WARNING INJURY CAN RESULT!

The following procedure requires you to touch fan hubs with objects or to use objects

to stop the fan blades from moving. Use caution when working near the cooling fans

with the covers removed from the oscilloscope. The cooling fan blades are exposed on

one side and can be hazardous. Be careful not to touch the moving fan blades with

any part of your body.

If the oscilloscope still shuts down, follow these steps:

1 Replace all the case fans.

2 Reset the logic by removing AC power for 30 seconds and make all of the case fans

so they cannot rotate. For example, have two people hold the four fan hubs or insert

an object between the blades of each of the fans.

3 Power the oscilloscope back on. If it shuts down again, the fan sensing and shutdown

function is operating properly. Replace the backplane.

If the PRED FAN FAIL LED is Lit

In addition to four case fans, there is also a single fan attached to the backplane

assembly that cools the trigger ICs. It is possible that this fan failed, or that the rotation

sensor for the fan failed. This sensor lets the oscilloscope know that the fan is turning.

If the sensor is faulty, the oscilloscope may think the fan is not working when it actually

is.

If the PRED FAN FAIL indicator LED on the backplane assembly is lit, the system

thinks there is a trigger ICs fan failure. To check, reset the sensing and shutdown logic

by removing the AC power until the green LED on the motherboard goes out (or just

wait 30 seconds). Then position yourself so you can see the trigger ICs fan on the

backplane assembly. Because this fan is on the bottom of the backplane it is somewhat

hidden by the acquisition assembly. Look down the backplane board to see it from

above. (See Figure 4- 15.)