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Either lead may also be used to connect the SA150 and SA200 to most other manufacturers’ pre-amplifiers which use a 5 pin 180° DIN socket with the output signals on pins 1 & 4. The phono sockets may also be used to connect the SA150 or SA200 to a suitable pre-amplifier. For best results only interconnecting leads of the highest quality should be used. The input impedance of both the SA150 and SA200 is 20 kii and the voltage gain of each channel of both models is 29dB (28.3 times). This is equivalent to an input sensitivity of 1.00V r.m.s. for 100 Watts r.m.s. into 8 ohms for the SA200 and 0.87V r.m.s. for 75 Watts r.rn.s. into 8 ohms for the SA150. These figures ensure that both power amplifiers should work with almost all pre-amplifiers and signal sources which provide nominal outputs of between 500mV and 2V r.m.s. If in doubt consult your dealer. 5 pin 180° DIN (DIN socket, pins 1 and 4. no conncction) Figure 5 L R Fuses 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 programrfie 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 SA 150 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. Mains Fuses All models are fitted with an anti surge (slow blow) 20mm x 5mm diameter fuse, designed to protect against faults in the amplifier, transformer and mains switch. The values are shown below: SA200 (all voltages) 5A SA150 (220/240V) 1.6A SA150 (120V) 3.15A THESE FUSES ARE NOT USER REPLACEABLE Should the SA150 or SA200 fail to function at switch-on the fault is probably external to the amplifier. In particular, check the fuse in the mains plug (and distribution board, if used) before suspecting the power amplifier. The switch-on surge currents of the SA150 and SA200 are very great which is why a 10 or 13 Amp fuse is recommended for the mains plug. You should also ensure that the IEC mains socket is pushed seucrely home into the IEC plug on the back panel of the amplifier. Inspecting and Changing Fuses In order to inspect or change the fuses you will need to remove the top cover (see Figures 6 and 7). BEFORE REMOVING THE COVER ALWAYS SWITCH OFF THE AMPLIFIER AND DISCONNECT THE MAINS SUPPLY. NOTE THAT THE MAINS FUSE REMAINS LIVE WHENEVER THE AMPLIFIER IS PLUGGED INTO THE MAINS, EVEN WHEN THE AMPLIFIER SWITCH IS IN THE OFF POSITION. To remove the top cover use a No 1 ;Posidriv’ screwdriver to take out the three black screws located along the top rear edge of the amplifier, above the heat-sinks. The cover may then be lifted ...

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