No power to switched ac plugs on back of unit
SOURCE: no sound from htr-5840 when switched on. I hear
These units have protection circuits that will prevent the speaker relay from engaging if there is a problem detected. There is also a circuit that causes a delay in the engaging of the relay to allow the amp to "settle in". This prevents the old "thump" that was common in older models when the set was first turned on. In your case, either the RC circuit is faulty causing excessive time to pass before turning on the relay, or there is excessive voltage floating around that the protection circuits are detecting and thus preventing the relay from turning on.
In any case, this will require additional diagnosis using some test equipment. This is not a problem that will be easily resolved remotely. Please bring this unit to a repair shop for an estimate. Once you have that info, we can assist with the actual repair.
Dan
SOURCE: Yamaha receiver model HTR-5840 will not switch
By fuse OK you do mean the one inside it? If so check the power switch, then check the power transformer.
SOURCE: fuse has not blown but
Generally speaking, an amp attempts to protect itself from heat, shorts, overloads and operator exuberance by refusing to turn on or stay on.
Overloads can be from excessive periods of high output or marginally low impedance loading by the speakers; and shorts would be wiring issues or a speaker blowing up.
You should be able to feel if it's hot. WHY is it overheating? Make sure it has sufficient ventilation on all sides and that vent holes are not blocked by dust balls. Ensure the fan (if equipped) is running as designed (some only operate on demand). Clean dust and debris from it.
If the amp comes back on after cooling, you're lucky. They only have so many self-protection cycles in their lives so continuously resetting or cycling their power without addressing the cause can do more harm than good.
If it protects immediately on a cool power up you should disconnect the speaker connections and try it 'nekkid'. If it comes up then diagnose which lead(s) are shorted. If it does not come up the problem is internal and should be left to an experienced and competent hands-on tech.
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