My adcom gfa5500 .most of its output mosfets are shorted.
I m able to get the output mosfets. BUT,when i check other components,i found out the value of R 23 of the left channel is different from the rigt one.since i dont have the schematic.i neeeeed help!!!!
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Re: my adcom gfa5500 .most of its output mosfets are...
The colour code or the value it states on R23 should give you the reading you will see on a test meter on the Ohm setting. If the value doesn't match the colour code of the resistor then you should replace it. It's best to take any resistor out of the circuit to test as strange readings can be caused in circuit. The same applies to the left channel one. Ohm meters are not expensive if you don't have one and can be got from various places that sell electronics parts etc. Some car part dealers sell them. They are a worthwhile investment and can be used for many types of problem.
It's likely that it's a basis resistor and failed when the power jobs went.
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Did you checked balanced impedance?load speaker impedance vs PA output?or PA might over driven,causing a trouble on the pre-amp to power amp circuits and components damage,
need to recheck related components on the pre-driver up to main output section,
Note: That,blowing of fuses with the same rating is an indication of trouble/shorted in a circuits that driven on it,
Your amplifier is having a serious fault within preventing further damage to the amplifier. If could be a failure of the output mosfets, failure of the predriver, failure of the bias to the output mosfets, short inthe speakers- check this out- fault inthe error amp section for wrong current indiication or malfunctions in the mother board. All of this will need careful location of the fault by checking ont these stages. Porceed only if you are competent or seek help. Good day
The driver circuits should be just before the outputs in the circuitry. The easiest way to check this circuit is to remove the outputs and turn on the unit. Measure each of the transistor pads relativce to ground for DC voltage. You should see the following: B+,0.6V (or 1.1V), and 0V on one transistor and negative values on its compliment. If you have questions, measure the pads and post the measurements here. In some cases the output transistor needs to be in place to get the values above, so if yours don't measure that way, just post what you get and we'll continue from there.
Adcom systems in general are compact and not the easiest to work on. There are no specialized tools required. Just be careful as there can be wires that are short that can be damaged. Make sure that the driver circuits are OK prior to jsut replacing the outputs. If you don't you may just blow the replacement parts as well.
Have it serviced. Do you know what GFA stands for. People at Adcom do have a great sense of humor. Take it only to a high end audio servicer. Contact Adcom. This is good stuff you wouldn't want a hack working on it.
Any fuse blowing is caused by a shorted component in either the power supply section or main audio amp part. Follow the fuse circuit and see where it leads you. Look around for burnt of damaged parts. Suspect anything sitting on a heat sink. The most common culprit is the audio amp main transistors, especially if someone shorted the speaker leads together. In the power part it could be the transformer, the large Electrolytic capacitors, rectifier, or voltage regulator. Some amps use an IC for amplification and this can blow the fuse.
Try just the power amp on ..nothing connected no Dakiom thingy either. It's a matter of elimination. Start at the output device and work back. Keep the Dakiom out of the loop. If there's hum with just the Adcom..then it's the ADCOM
Remove the output transistors and measure each of the sets of 3 pads and report the voltage readings here. I suspect that you have either a blown driver circuit or output transistors. The voltage readings will give me an idea on where to start looking for specifics.