TONEOHM 950 OPERATOR MANUAL
4-4
Causes of Shorts on Multi-layer Boards
Polar Instruments has evaluated many defective multi-layer boards (both bare and assembled) from a
range of manufacturers and found that the cause of most of these faults are the same as on single or
double-sided boards (e.g. solder bridges, bent component leads etc.) Where the short occurs internally
this is usually associated with a via hole. Thus it is usually possible to locate the short to a point that is
accessible from the surface of the board.
Connection
Connect the four Plane Stimulus leads to the corners of the shorted plane as shown in Figure 4-2.
BLUE LEAD
RED LEAD
GREEN LEAD
YELLOW LEAD
Figure 4-2 Plane Stimulus Connection
The positions of the Stimulus sockets on the front panel correspond to their positions on the board under
test (e.g. blue in Top Left corner, red in Top Right corner, etc.).
• Connect the colours as shown to ensure the LED Direction Arrows indicate the
correct direction. Connect as close as possible to the corners of the plane.
• If the short is between two planes, select either plane but ensure the leads are all
connected to the same plane. This plane is referred to as the stimulated plane.
• If there are via holes closer to the corners of the plane than component leads, then
solder a short length of tinned copper wire to the holes and connect the Stimulus
leads to those wires.
• Connect the Plane Clip to the other side of the short. If the fault is a plane to plane
short, connect the Clip to the other plane (referred to as the un-stimulated plane). The
Clip can be connected to any point on the track or plane.
• Press PLANE SHORTS, which will light the STANDBY LED. In Standby the display
reads "1---".
• Check the Plane Stimulus leads are connected correctly, then press PLANE
SHORTS again. This will turn on the Plane Stimulus and light the ACTIVE LED.
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