A&R Power Amplifier SA200 Podręcznik użytkownika - Strona 9
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Drukuj stronęFuses
Output Fuses
Both the SA150 and SA200 are fitted with fuses (one per channel) in their output circuits to
provide extra protection for both amplifier and loudspeakers in the event of medium to long term
overloads. Each fuse is placed within the feedback loop of its power amplifier channel to eliminate
the audible effects of having a speaker fuse in series with the loudspeaker.
In addition, in the SA200
only,
the circuit is so designed that, if an output fuse blows, not only
will the sound from the loudspeaker cease but the overload LED on the front panel will glow red
almost continuously if any attempt is made to play music through the system at normal volume
settings. This is a certain indication that one or both speaker fuses have failed and need replacing
(see over).
Choosing Output Fuse Ratings
The output fuses fitted to the SA150 and SA200 are of a sufficient value to ensure that the
amplifier will drive 4 ohm loudspeakers satisfactorily, with little risk of the fuses failing on normal
programrhe material. However many loudspeakers have a much higher average impedance than
4 ohms and in order to provide them with the optimum protection against overdriving, it may be
desirable to fit output fuses of a somewhat lower rating. Suitable spares for nominal 8 ohm
loudspeakers are provided with the SA150 and SA200, as shown in the table below. Some
suitable values for fuses (not supplied) which may be used with 16 ohm loudspeakers are also
shown. In all cases it is wise to use the lowest fuse value possible which does not fail on normal
programme material and some experimentation may be worthwhile here. Similarly, if
loudspeakers are used which will not accept the full power output of the amplifier, then the fuses
should also be down rated in order to provide the loudspeakers with best possible protection
against overload. If in doubt consult your dealer or the loudspeaker manufacturer.
Nominal impedance
of loudspeaker
Suggested fuse value
|
SA150
SA200
4 ohms
2.5 Amp
3.15 Amp
8 ohms
1.6 Amp
2.0 Amp
16 ohms
1.0 Amp
1.25 Amp
In all cases the fuses used should be 20mm x 5mm "fast blow" types.
IN NO CIRCUMSTANCES SHOULD "SLOW BLOW" OR "ANTI SURGE" FUSES BE USED,
OR VALUES GREATER THAN THE HIGHEST LISTED IN THE TABLE ABOVE. THIS
WOULD RESULT IN INADEQUATE PROTECTION OF THE AMPLIFIER AGAINST
OVERLOAD AND WILL INVALIDATE THE GUARANTEE.
Power Supply Fuses
These are—2.5 Amp fast blow 20mm x 5mm diameter fuses (model SA150).
These are—3.15 Amp fast blow 20mm x 5mm diameter fuses (model SA200).
THEY ARE NOT USER REPLACEABLE.
If any of these fuses fail there is probably a fault in the amplifier—do not change the fuses but
consult your dealer.