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EXERCISE 36 : SHORT LOCATION (II)
ACTION
Remove clip from U10. Leave the jumper in place across the pins. Remove BDO cable and
attach Short Locator probes to Auxiilliary I/O on BFL (See Schematic). Using the schematic as
guide probe across the IC pins where Link is present.
Turn the Tome ON (If not already on) and you will hear the differnent Tones the closer you
get to the short.
Note the differences in readings.
1) Probe Pins 16 & 18 on U10
2) Probe Pins 5 & 7 on U13
3) If you place the probes on top of the jumper you will see what a direct short will look like.
DESCRIPTION
So far, we have discovered that 2 pins on the bus are connected. However, because of the
bus structure these two signals appear at many places on the board. We must now find the
exact location of the short, using the Short Locator instrument.
The connections test in the previous test found LINKS between bus lines. The exact location
can be found with the Short Locator. This has an audible indication to allow you to
concentrate on the board while tracing the short. You can get close to the proximity of the
short by going to each IC in turn.
COMMENTS
There is no formula to work out how close you might be to the short by the reading you
have. The resistance read depends on track width, height, and length. Therefore the lowest
reading obtainable gets you the closest to the short.
