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3) INSTRUMENTS AND CONVENTIONS FOR PER-
FORMING DIAGNOSIS AND REPAIR
3.1) Instruments for basic diagnosis
The following are required:
-
a multimeter with the following scales:
Ohm: from 0 ohm to a few Mohm
Diode testing
Direct voltage (Vdc): from mVdc to 1000 Vdc
Alternating voltage (Vac): from 10 Vac to 700Vac
NOTE: You are advised to use an instrument with automatic scale
since it is not theoretically possible to predict the electrical
quantity to be measured when the machine has broken
down.
-
an DC ammeter clamp at least in class .5 with e.o.s. 1000A
pk.
-
alternatively to the ammeter clamp, a shunt can be used with
value 60 mV @ 150 A.
NOTES:
* Remember that other types of shunts can also be used, but accu-
racy is reduced with higher capacities, whereas with lower capa-
cities the measurement must be taken quickly to avoid overhea-
ting of the shunt
* Once fitted, the shunt is at welding potential
* The ammeter clamp is preferable as it is more practical
3.2) Repair tools
- Complete set of fork spanners
- Complete set of pipe spanners for hexagonal nuts
- Complete set of blade screwdrivers
- Complete set of Phillips screwdrivers
- Complete set of Allen keys
- Crimper for insulated wire terminals (blue, red and yellow)
- Pliers for AMP contacts
- Tweezers and cutting nippers - type commonly used for
electronic components
- Tongs (dimensions suitable for closing gas pipe clamps)
- Welder for electronic components, minimum power 50 W
- Portable electric drill
3.3) CONVENTIONS.
By convention, when a measurement has to be taken between two
points, for example a
apply the red tip of the multimeter (a),while the black tip is applied
at the other end (b).
When a double arrow appears between two measuring points (e.g.:
c
d), the voltage to be measured is alternating (normally at
50 Hz), therefore it does not matter in which order the multimeter
terminals are applied.
In drawings and tables, when a voltage measurement appears refer-
ring to terminals of components such as DIODES, BJT, MOSFET and
IGBT, the multimeter is used in "diode test" mode (these measure-
ments are always taken with the machine switched off and normally
give values in the range +0.10 ... +0.90Vdc). In this case the fol-
lowing symbol is affixed beside the value to be measured
Junction measurement (multimeter in "diode test"
mode)
The following symbols will be used in the same way:
AC or DC voltage measurement (multimeter in voltme-
ter mode).
Resistance measurement (multimeter in ohmmeter
mode).
Current measurement (ammeter clamp or shunt + mul-
timeter in millivoltmeter mode).
Frequency measurement (multimeter in frequencymeter
mode).
The measuring conditions (power source on/off, MMA/TIG opera-
ting mode, erc.) are always clearly indicated beside the values to be
measured.
The connector terminals are indicated by the name of the connector
followed by a slash and the number of the terminal; for example
CN1/ indicates terminal of connector CN1.
Unless otherwise specified, all the measurements must be perfor-
med with the boards fitted, together with their connections.
Remember that the first of the tests to be perfor-
med is the VISUAL CHECK!
The visual check reduces troubleshooting times and directs
any subsequent tests towards the damaged part!
b, the arrow point indicates where to
5
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