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the reason that audio amps pop their output transistors because of incorrect loads.some owners are trying to get 90 watts out of a 9 watt amphifiers.
if an amphifier specs says 8 ohm speaker load you can not reduce that load.if you take a 8 ohm speaker and parallel another 8 ohm speaker the load is know is know 4 ohm etc. the output transistor come under an extreme load and reads it as a short and they open up try to compansate power.this draws on power supplies.this stresses and increases current draw.the worse thing to electronic circuits is heat and then a melt down.
you can take a one watt amphifier and make it sound like a thousand watt amp.this is done by use enegry efficient speakers systems.enegry efficient voice coils and cross overs.my pioneer receiver is only three watt per channel using radio shack nova twenty four speaker system.my friends can not beleive sound that it has they claim it sound like thousand dollar system.
so if you want parallel two speakers to an amp with 8 ohms output to get the correct load you buy a pair of 16 ohm divided by two = 8 ohm.so and so forth. this applies to 16 ohm or 32 ohm to parallel you buy speaker so sum equals the load in ohms.
to trouble shoot with out a print is to find the output transistors if they are colored one gray or black is you npn positive collector voltage center pin on transistor is collectors on some power amp theirs exceptions but if your amp is not three or four thousand U.S. dollars this does not apply, but w /m/department store speacials it does.
the transistor is green in color this is pnp collector is negitive voltage or chassic ground depending on power supply configuration. theirs two channels so their should be two pairs of one gray and one green.
to trouble shoot disconnect collectors on all output transistor then check power supply for an output this could be anyware from 12 volts to 42 volt depends on power level for that amp.most of the time most amp failure are going to be output transistors.this is because power supply goes to this transistor first.so for all those who blast their amps in new york so teens in ISEREL can hear music the outputs ore going to blow.
to fine out what your power supply is again fine large capacitor in that part of the amp.read voltage and divide by two sum will be power supply output. simple yes.
their are two types of power supplies half wave and full wave (full rectifier bridge
if their two capacitiors that are for example 4700uf 50vdc in front of the bridge in power supplies pnp power outputs is above chassic ground a have neg voltage on their collectors.so if 24 volt dc it could plus 24v and a minus24v.the power transformers my or may not have a center tape depends on design or features to that amp.
theirs a thermocoupler between output to shut down amp in over heat conditions.on some amps.this part goes bad often b+ voltage one side to collector of the outputs.
Post edited by: hobbist, at: 2008/05/10 21:15
Post edited by: hobbist, at: 2008/05/12 14:50
Post edited by: hobbist, at: 2008/05/14 14:05
Post edited by: hobbist, at: 2008/06/05 18:38
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