Main Board Circuit Checkout; Power Supply Checkout - Racal Instruments 3151 User Manual

3151 And 3151A User Manual
Main Board Circuit
Checkout
Power Supply
Checkout
The Model 3151/3151A is made of two boards. The large board (Part
Number 7100-2370) is the main board. There is a smaller board
mounted on the main board with three connectors (Part Number
7100-2360). This smaller board is called the engine board . The
following checks are made on the main board. To gain access to
components below the engine board, it may be necessary to remove
this board entirely. To do so, remove the three screws that tie the
engine board to the main board, grasp the engine board from both
sides and pull away from the main board.
It is suggested that the first step in troubleshooting the Model
3151/3151A would be to check the power supply rails. If the various
supply voltages within the instrument are not within the required
limits, troubleshooting the remaining circuits can be very difficult.
The supply voltages are supplied to the Model 3151/3151A through
the backplane. In case of a "dead short" between one of the supplies
to the common ground, disconnect the entire supply section from the
remaining circuitry, and then determine whether the problem is in the
power supply or in the remaining circuits.
A few preliminary checks could help here. First remove the Model
3151/3151A from the VXI chassis. Turn on the VXI chassis and
verify that the supply voltages are available directly on the backplane
sockets. Check the following supplies: +24V, -24V, +12V, -12V, +5V,
and -5.2V. Check the ripple on these lines using an oscilloscope.
Plug an extension card into one of the slots and plug the Model
3151/3151A into the extension card. Turn the chassis power on and
repeat the supply voltage tests as above. If one of the voltages is
missing or not within the specified range, it is possible that one of the
supply lines is shorted inside the Model 3151/3151A. Remove the
filter chokes L12 and L13 if there are problems on the +24V or -24V
lines; remove L8 or L9 if there are problems on the +5V or -5.2V
lines, or remove L10 or L11 if there are problems on the +12V or -
12V lines
Maintenance and Performance Checks 5-19