QuestionQUESTION: Hello - My Luxman L580 seems to turn on however the familiar 5 second(approx) delay function click doesn't happen so no audio. When I turn off the amp I do see the output l/r leds flash. Thank you in advance for any assistance.
ANSWER: When the relay does not click it means the speaker connections are not coming up. It is likely a power supply failure which can be caused by internal power supply problems or the audio output section is melting down from dry silicon transfer grease in the power transistors.
Better have a service tech look at it. If you are electronically gifted let me know and I will give you some comments on how to troubleshoot it. But, you will need a VOM and know how to take voltage measurements.
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QUESTION: Yes I am electronically gifted and do know how to use a VOM. Thanks again for your assistance...Rick
ANSWER: ONE:
First, let's assume it is the power supply. Place the voltmeter on one of the big caps in the power supply ripple filter area and look at the voltage when it is first turned on. If the voltage goes up and then back down to some lower voltage - or to zero - after the 5 seconds or so it is a sign the caps are bad or the protection circuit is shutting down the power. If you know how to check the filter caps do that - or disconnect them (probably 2 of them in big cans) to see if the voltage stays up after the set is turned on. If they are bulging it is a bad sign!
The reason for starting with the electrolytic caps is because they are the shortest life of all the components in the amp. They become gassy and short down with age - or sometimes go open. In fact, it is not a bad idea to replace them even if they are still good because they will be going out soon anyway. As long as you use good grade replacements with the same or greater ratings they will work fine.
TWO:
First measure the dc voltage at the speaker terminals with no speakers connected. If there is more than a few millivolts it is an indication of trouble in the output circuitry.
If the problem is at the output stages try disconnecting the dc voltage lines to the output transistors so there is no power getting into them. This should allow the amp to power up normally. Reconnecting the power transistor dc lines will return it to the former condition. If the power transistors are mounted on big heatsinks they have maybe run too hot and failed from overcurrent conditions. This is often caused by the thermal grease between the transistors and the heat sink drying out and not allowing sufficient heat transfer. You can sometimes see by inspection that the grease looks dry.
Those are the two places to start.... not guaranteeing either one is the cure, but that usually takes care of 90% of power amplifier repair.
Then, let me know how it goes.
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QUESTION: - The voltage stayed constant on the large caps. The large caps measure coeectly - as I have a Capacitance meter. With no speakers connected there only was a few mVolts on the speaker terminals.
I checked all visible fuses. I can't see any signs of bad capacitors.
The thermal grease looks good where the output transistors are mounted.
AnswerSo, it wants to be a tough one, eh?
Back in the beginning you said the relay click does not come on? I wonder if the relay or the relay activation circuit is defective in some way?
And, can you check for audio right at the outputs of the power transistors? If you can get audio at the transistors but not at the output terminals then the amp is okey but the delay relay is not! This relay is to keep the audio disconnected until the voltages become stable before speakers connect - to avoid the "thump" that you hear in amps that come on directly to the speakers. If you have access to a scope that would help you look at the transistor outputs.
Maybe that will solve the problem.
