Chapter One About Maintenance
1.1 Safety precautions
1.1.1 Power supply
1.1.2 Precautions for antistatic
When servicing audio power amplifier, the servicing personnel pay special attention to the power
board with 220V AC, or else the improper operation will lead to body damage. The alternate current
which outputs to power amplifier board through power board is also up to voltage with about 50V; when
servicing, short-circuit and joint welding cannot occur, or else the elements will be burnt out and trouble
range will be enlarged.
Movement and friction will both bring static electricity which causes serious damages to integrated
IC. Though static charge is little, when a limited quantity of electric charge is added to large-
scaleintegrated IC, as the capacitance is very small in the meantime, now the integrated IC is very much
easy to be struck through by static electricity or the performance will decrease. Thus static electricity
prevention is of extraordinary importance. The following are several measures to prevent static
electricity:
1. Use a piece of electric conduction metal with the length of about 2 metres to insert into the earth,
and Fetch the lead wire from the top of the surplus metal and connect to the required static electricity
device. The length and depth of the metal embedded under the earth should be determined according to
the wettability of the local soil. For humid places, it may be shorter, and longer and deeper for dry places.
If possible, it can be distributed and layed in terms of “#”shape.
2. On operating table-board, the antistatic table cushion should be covered and grounded.
3. All devices and equipments should be placed on the antistatic table cushion and grounded.
4. Maintenance personnel should wear antistatic wrist ring which should be grounded.
5. Places around the operating position should also be covered with electric conduction cushion or
Painted with antistatic paint.
- 1 -
