Mustang M1008/D, M/8M, M2508/D, M100/SD Faults Symptoms and Checklist, Fault Symptom Checklist

MACRO range installation manual. Issue 6

FAULTS - SYMPTOMS AND CHECKLIST

The following list of fault symptoms and check points cannot be considered as comprehensive, but as a guide to the most likely faults and causes. We assume that the input sources and loudspeakers are properly connected and in good working order. Be sure to check these carefully first before investigating the amplifier.

	FAULT SYMPTOM	CHECKLIST
1	Sound off, main power switch lamp off	AC mains fuse, mains lead, mains power, mains switch. DC supply, fuse, or leads.
2	Sound off, main power switch lamp on	Internal AC/DC power fuses, output transistors, input connections, module edge connectots,
		output transformer continuity, pre-amplifier stabiliser module, line driver module, priority channel
		not being triggered, input module not being set by dedicated jumper pins, input module being
		muted by operation of higher priority.
3	Sound faint	Module sensitivity adjustment, incorrect output connections, overload on mixer facility socket,
		incorrect input pin selection, incorrect choice of input module.
4	Sound loud but distorted	Incorrect choice of input module, incorrect module sensitivity setting or pin selection, incorrect
		loudspeaker load, volume control too far advanced, system requires amplifier of greater power
		or more efficient loudspeakers, master control set too low.
5	Sound distorted on bass peaks	Bass controls too high, poor quality 100V line loudspeaker transformers. See also No.4 above.
6	Sound distorted and low	Incorrect choice of input module, incorrect module sensitivity setting or pin selection, incorrect
		loudspeaker load, partial loudspeaker line short, output transformer short circuit, master control
		set too low.
7	Case gets very hot	Incorrect (excess) loudspeaker loadings, see page 18, parasitic oscillation (usually
		accompanied by soft hum and mild distortion and appears and disappears at a certain treble
		control setting) see 8 below, insufficient ventilation, see page 31
8	Parasitic/supersonic oscillation	Insufficient screening on high sensitivity input signal cables, insufficient earthing,
		loudspeaker/input leads adjacent or parallel for some length, unloaded input line, incoming
		parasitic on signal line from ancillary equipment, braiding on input cable disconnected or
		intermittently faulty.
9	Soft hum - volume controls down	Earth/hum loop - see page 25, power supply capacitor failing, induced magnetic field from
		nearby mains equipment.
10	Hum	Incoming hum from ancillary equipment, induced hum on sensitive input cables, incorrect
		earthing to amplifier or ancillary equipment, earth/hum loop, see page 25
11	Hiss	Excess treble, signal noise incoming from ancillary equipment, unloaded input signal line,	noisy
		input module.
12	Fizz	Interference from lighting dimmers, dimmer lines, faulty fluorescent lights, earth/hum loop,	see
		page 25
13	Loud harsh hum	Disconnected signal input braiding, or buzz earth/hum loop, see page 25
14	Intermittent loud cracking	Strained input module edge connectors, dirty edge connectors, intermittent input lead
		connections, dirty voltage selector pins, dirty mains plug pins, loose mains fuse, radiated
		interference from thermostat etc. see also No.5 above.
15	Howling or ringing and booming	Acoustic feedback between microphone and loudspeakers
16	DC fuses blowing	Failed output transistors and/or driver board
17	Mains line fuse blowing	Mains switch suppressor shorted, main rectifier failed, mains transformer failed, output
		transistors failed
18	Input channel off	Incorrect priority triggering, module edge connector, module muted by higher priority, input
		signal fault, module not set to passive mode
19	Incorrect signal priority	Incorrect setting of PCB priority switches or of priority/passive jumpers
20	Intermittent sound	Strained input module or driver board edge connector, fractured input cable, worn volume control
		track.
21	Mixer AC supply fuse blowing	Regulator module
22	Power switch unlit	AC (and/or DC) power missing, switch lamp, internal lamp regulator, power fuses.
23	ERROR lamp flashing infrequently	Signal bass peaks triggering protection infrequentlycircuitry
24	ERROR lamp flashing frequently	Loudspeaker load excessive, or faulty threshold frequently setting.
25	ERROR lamp on permanently, no audio	Faulty power section module.
	output
26	Rhythmic clicking	Incompatibility of internal charging system and earthing in multi-amplifier installation, red wire on
		Power Management PCB not disconnected

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