Philips PM2519 - Page 55

4.
4.1.
41.
4.1.2,
4-1
FAULT-FINDING
WARNING: The opening of covers or removal parts, except those to which access can be gained by hand
is likely to expose live parts, and accessible terminals may also be live.
The instrument shall be disconnected from all voltage sources before any replacement or
maintenance and repair during which the instrument will be opened.
tf afterwards, any adjustment, maintenance or repair of the opened instrument under voltage
conditions is inevitable, it shali be carried out only by a skilled person who is aware of the hazard
involved.
Bear in mind that capacitors inside the instrument may still be charged even if the instrument is
separated from all voltage sources.
GENERAL
Service hints
If servicing is necessary the following points should be taken into account in order to avoid damaging the
instrument.
Take care to avoid short-circuits with measuring clips and hooks if the instrument is switched-on, especially
near the input terminals when high-voltages are present.
Use a miniature soldering iron (35 W max.) with a thin cleaner or a vacuum soldering iron.
Use an acid-free solder.
— When fault-finding, remove top and bottom covers and connect an external power supply of +7 V to
TP1005 (+) and TP1007 {—).
After repair, the instrument should be recalibrated.
Fault-finding procedure
This chapter gives a fault-finding procedure to locate the faulty section in the instrument.
From this procedure the faulty parts can often be found by using the detailed flow-charts.
NOTE: The procedure is only intended as an aid to fault-finding, and obviously the faulty component
will not be found in every case.
Measuring instruments used:
— Digital multimeter
— Oscilloscope
— Counter
— Signature analyser
After repair, the preset values, which are stored in RAM, must be reset. To do this short-circuit TP1001 and
TP1002 for one second in the position p>,