Selco Genesis 1700 AC/DC, Repair Manual, Page: 30 / 124

9) INSTRUMENTS AND CONVENTIONS FOR
PERFORMING DIAGNOSIS AND REPAIR
9.1) 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.
SEVERAL MEASURAMENT SHOULD BE PLACED ON
CONNECTORS SIDE. PAY PARTICULAR ATTENTION IN
ORDER TO AVOID ANY ACCIDENTAL SHORT CIRCUIT
BETWEEN CONNECTOR'S PIN OR TEST LEADS. THE USE
OF THIN CONDUCTORS AS RESISTANCE LEADS COULD BE
HELPFULL ON MEASURAMENT STAGE.
- an AC/DC ammeter clamp at least in class 2.5 with e.o.s.
300A pk.
9.2) 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
- Dynamometric screws driver for fix M3 with adjustable
torque range 1÷3Nxm tolerance 0.1Nxm
- Crimper for insulated wire terminals (blue, red and yellow)
- Pliers for AMP contacts
- Tweezers and cutting nippers - type commonly used for elec-
tronic components
- Tongs (dimensions suitable for closing gas pipe clamps)
- Welder for electronic components, minimum power 50 W
- Portable electric drill
9.3) Conventions
By convention, when a measurement has to be taken between
two points, for example a b, the arrow point indicates
where to 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 (nor-
mally at 50Hz or 60Hz), therefore it does not matter in which
order the multimeter terminals are applied.
In drawings and tables, when a voltage measurement appears
referring to terminals of components such as DIODES, BJT,
MOSFET and IGBT, the multimeter is used in "diode test"
mode (these measurements are always taken with the machine
switched off and normally give values in the range +0.10 …
+0.90Vdc). In this case the following 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
voltmeter mode)
Resistance measurement (multimeter in ohmmeter
mode)
Current measurement (ammeter clamp or shunt +
multimeter in millivoltmeter mode)
Frequency measurement (multimeter in frequen-
cymeter mode)
The measuring conditions (power source on/off, MMA/TIG
operating mode, etc.) are always clearly indicated beside the
values to be measured.
The connector terminals are indicated by the name of the con-
nector followed by a slash and the number of the terminal; for
example CN1/2 indicates terminal 2 of connector CN1.
Unless otherwise specified, all the measurements must be per-
formed with the boards fitted, together with their connections.
Remember that the first of the tests to be per-
formed is the VISUAL CHECK!
The visual check reduces troubleshooting times and directs
any subsequent tests towards the damaged part!
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