5
If you accidentally touch the probe to a wrong pad not on the shorted circuit, like maybe
ground, and LeakSeeker notices the huge change, it intentionally waits a second before
accepting the huge change and recalibrating. The delay is intentional; if you accidentally
touched the wrong pad (like a ground), this delay gives you the time to change your mind
as long as you lift off of the pad before the WAIT LED comes on and recalibration is
complete. You should always double-check your progress by touching the previous pad--
-the pitch should be lower than the pad closest to the short. If you goof, just press
RESET and start off the last valid solder pad.
On older boards with large traces, or on multi-layer boards with groundplanes, you may
find that many pads close to each other may have the same pitch. Use the highest GAIN
setting and now you will see and hear a slight change between the two pads. The pad with
the highest pitch is your objective. When the tone no longer changes and the WAIT LED
is off, the window is perfect.
As you touch each pad, remember to always go back one to double-check that the tone is
lower (or gone completely as that window is now long gone). At some point, the beep
will be highest in pitch at only one pad along the trace. This is the short, and may be the
location of the defective component. If you continue past this pad, the pitch will start to
go lower and the distance indicator will start to head towards the red indicators. If you
backtrack, the pitch will always be highest at the pad with the lowest resistance, and of
the possible defective component.
But what if the highest pitch can’t be the bad part?
If the highest pitch comes from a pad that is a jumper or wire, or coil or transformer, for
example, a component that is supposed to conduct, this means that the defect is probably
on the other side of the component, in another area of the board. For example, if you are
tracing a short at the collector of the horizontal output transistor and find that the highest
pitch is at the flyback transformer primary, this does not necessarily mean that the
transformer is shorted; the short may be on the other side of the winding, at the B+
supply. Follow it like a detective, as you may find that you may be jumper-hopping, coil-
hopping, possibly even board-hopping, for example from the HV board, to the supply
board and so on, to where the bad part actually is. The obvious parts that could be bad are
parts that should never show as a low resistance in the first place, such as a capacitor,
cathode of a diode, B+ pin of an IC chip and so on.
Using the Hot/Cool thermal test method
If the defect is several ohms, you can search for the defective component in another,
much easier way. To keep your hand free to hold a can of freeze spray or a soldering iron
or hot air blower, use the extra plug-in test cable supplied with LeakSeeker that has the
