Load Protection Methods; Cleaning; Fuse Selector Nomograph For Loudspeaker Protection; Relay Controlled Protector With Overload Indicator - Crown DC-300A Instruction Manual

--10
N
a
--30
FIG. 3-3
FUSE SELECTOR NOMOGRAPH FOR
LOUDSPEAKER PROTECTION
Another form of load protector is shown schematically
in Fig. 3-4. Whenever the load is overdriven, a relay
switches a lamp in series with the load, smoothly
relieving the overload. The lamp then doubles as an
overdrive indicator as it glows. If overdrive is unreason-
ably severe, the lamp will serve as a fuse. By adjusting
the relay tension adjustment and the protection level
control, this system is useful from 25 to 200 watts for
a typical 8 ohm load.
FIG. 3-4
RELAY CONTROLLED PROTECTOR
WITH 0 VERLOAD INDICA TOR
400
300
200
l - -
d - -
A common problem which causes damage and irritation is
the turn-on thump problem typical to many signal sources.
Fig. 3-5 shows the schematic of a muter which, when
inserted in the input signal line, mutes for several seconds
before connecting the source to the amplifier, thereby
eliminating turn-on transients. It also removes turn-off
transients occurring after the relay drops open (=O.l sec.).
FIG. 3-5
TURN-ON- TRANSIENT MUTER FOR
LOAD PROTECTION

3.5 CLEANING

The CROWN DC-3DDA has a rugged anodized front panel
for life-time service. The panel can be cleaned with a
moist cloth and mild detergent. Never use steel wool,
scouring powder, lye solution, or any strong abrasive
cleaner as these will damage the panel's finish.
The back chassis should require no more cleaning than
periodic dusting with a clean dry cloth. The use of de-
tergents, abrasives or other cleaners may remove the
fine film of oil from the black anodized chassis which
is used to increase its surface lustre.