Question about Cambridge Audio Audio Players & Recorders
My next door neighbour has just brought 'round his Cambridge Audio A5 integrated amplifier. It's blown up.
Keeps blowing fuses, i suspect a faulty output/driver stage.
i'm an electronics engineer working (for my sins) in aerospace. i design and build valve amplifiers for audio in my spare time.
A downloadable circuit diagram would be very helpful in curing this poorly circuit. Any ideas where i can get one for free ?
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Posted on Jan 02, 2017
SOURCE: Audio Amplifier JVC Model A-GX3
If the service manual is not available on the JVC websites then you should just Google search "JVC A-GX3 service manual" There are many websites that archive manuals. You'll probably have to pay for a copy. Why can't you disassemble the unit and see the output transistor numbers first? More importantly how do you know this is the fault?
Posted on Sep 22, 2007
An audio amplifier is a general term that applies to any amplifier specifically designed to cover the audio spectrum, and usually referres to power amplifiers (of any power from micro headphone amps (like the headphone audio amplifier circuit in an ipod) . to power amps like the ones used at rock concerts that are several thousand watts).
An OP-AMP is an Operational Amplifier, which refers to a type of amplifier circuit. Op-Amps can amplify audio, but are not restricted to it. They are used in many things from audio circuitry to signal conditioning, and sensing from all kinds of equipment from seismometers, to light sensors, temp sensors, insturmentation amps, lab amps... RF amps etc...
There are many many different types of op-amps that are designed for many different applications. Mostly the parameters are frequency response, gain, and input/output impedance.
Op-amps usually come in an IC package of some sort. The most common are 8 pin DIP package types.
Op-amps do NOT handle power. (although there are some hybrid power op-amps available, they are specialty devices) The term op-amp refers to the ability of the amplifier to be manipulated mathematically by external values. (i.e. resistors set up to add, subtract, or multiply the value of the input signal) Hence the term OPERATIONAL amp, because it is performing mathematical operations on the signal. (They were first used in analog computers, allowing the voltages to be added, subtracted, and such, and displaying the resultt by directly reading the voltage value).
They handle only small signals, and require being followed by a POWER amp to do anything useful, such as drive a spleaker, or a relay, or a transducer.
For your question, most all audio amps consist of stages.
There is an input/pre-amp stage (this is usually where the eqalization, signal processing, and bass/trebel tone controls are implelented) and a power amp (output) stage that takes the signal fromthe pre-amp and raises the voltage and current to a sufficient level to drive speaker.
The input/pre-amp stage is most usually composed of a series of op-amps. Op amps also are responsible for the bass/trebel control, and the EQ.
There will most usually always be several Op-Amps in every Audio Amp.
Posted on Jun 12, 2009
If both speakers work okay on other inputs .Then cable from pre-amp to amp and main amp are okay. If phone RCA jacks go directly to electronics board .Then its possible solder on phono jacks need to be resoldered or other connections in that section.If unit needs repair you can also purchase a phono preamp from radioshack hook up your and use it on other good inputs such as CD etc..Please note PHONO inputs are only for turntables .If a non turntable input such as CD,TAPE,TV Etc is used on PHONE .Then you will overdrive this input .
Posted on Jul 21, 2009
Start with the basics first. 1. With the amp on, in each imput socket plug a dual end phono cable in and touch the right and left plugs with your finger. You should get a buzz on each speaker. No buzz and the channel at that terminal is not working. If none of the terminals buzz. Then the amp is dead.
If some buzz and others not you have a pre-amp problem.
2: Amp Dead. Could be A power supply. B main pre-amp. C Power Amp.
The power supply check for a fuse.
The main pre-amp will only effect both channels if an IC controls both.
The Power Amp will again only loose both channels generally if it is an IC. It will be attached to a big heat sink and have lots of pins comming from it.
If it uses transistors for the main amp, you can check these with an Ohm meter. With the power off place the leads on each terminal of each transistor. If the meter goes fully over (like when you touch the leads together) each way it has shorted.
The thing to remember when repairing stereo amps. Is that the amp is two identical amps joined together. So what happens one side will happen on the other. If both channels don't work look for something that is common to both.
PS never heard of 'cliperd'.
Posted on Sep 25, 2009
The 2 BIAS resistors of 47kohm, R333 R334, replaced with new 1W resistors. 1 resistor was totally open and 1 resistor was 55k.
It were 1/2W resistors, replaced them with 1W resistors. Very low cost repair for a High End amplifier. Should live for another 10 years.
Posted on Jan 08, 2010
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