Chapter 5 Troubleshooting & Maintenance RIGOL
Service Guide for DM3068
DM3068 Mainboard
(Front End Circuit)
(CPU)
Current Input Fuse Banana Socket
LAN/GPIB
LCD
Keypad
USB
Host
Board
Power Input
Floating Circuit
Grounding
Circuit
Power Input
Socket
Main
Voltage
Regulator
Circuit
Trig/VMC
Transformer
Fan
Figure 5-2 DM3068 circuit principles
2. The grounding circuit contains most circuits such as keypad, LCD, USB Host,
LAN/GPIB board, Trig/VMC port, fan and CPU.
3. The AC supply enters the meter through the wire and flows through filter board
to transformer. The voltage selector provides two voltage scales (one is 115V
and the other is 230V). The transformer reduces the ac voltage into multi-path
to supply for the floating (9V, one group) and grounding (an 8.5V and two sets
of 17V) circuits, respectively. Related rectification circuit and filter circuit as well
as voltage-stabilized circuit are contained in both circuits for transforming the
low ACV into the stable DCV to supply for each circuit. Note the rectification
circuit, filter circuit and most voltage-stabilized circuits from the floating circuit
are on the main voltage regulator board.
When measuring, the CPU sends commands to control the analog front-end to
switch between function and range and then the analog front-end returns the
result from A/D transform or frequency counter to the CPU for correcting. The
measured result is then displayed on the screen.
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