Question about Onkyo TX-SR705 Receiver
There are a few different potential causes for the symptoms that you describe.
1) Power Supply out of tolerance, is unstable (drifting)
2) Final Amplifiers are damaged, likely due to heat
3) Temperature compensation is faulted.
#1. This is the likely candidate since you stated that you think it is overheating, and the unit is very hot. If the unit is hot enough to be uncomfortable, the fans need to be running. A power supply that has drifted away from tolerances for voltage output can wreak havoc on the other components, if it hasn't already. Shutdown can occur due to thermal reasons, or the output voltages have tripped a protection circuit.
#2. The finals are easily damaged by heat, hence the reason for the massive heatsinks, and forced air cooling. Since most finals are of a darlington configuration, the initial input transistors are likely to be the ones thar are damaged, and will have an unstable gain / HFe, which then affects the main transistors. Shutdown can occur if the finals draw too much current, and trips overload protection. This is likely what has happened, and the finals are continuously drawing too much power for even small signals. This is the only part of the unit where volume control would not have an effect. It just amplifies, usually by a fixed amount, whatever signal comes in.
#3. Temperature compensation works by changing the initial gain in different parts of the circuit so that other parts are not over driven / over worked and presented with too much of a signal that they can't handle. This is mainly directed towards te finals, though temp. comp. is likely built into them. This likely has failed as well, and caused #2.
As for being cost effective, that depends upon your specific situation. If there is a service center nearby, then you should take it there for an estimate. It might cost you $50-100 for this, but it will give you a rough idea of what needs to be done, and associated cost. Many places apply the charge for estimates to the actual repair bill. Some will also apply it to the purchase of another unit, provided you relinquish yours. Personally, I think that your receiver is a sweet setup, and is worth at least the cost of the estimate. If it has been exposed to conditions that may have shortened its life, then you might consider otherwise, or at least tell the service center to cut down on the amount of time that may be required.
Posted on Sep 10, 2010
It definately sounds like an overheating issue.. I have an Onkyo myself and I love it, but it definately gets hot when in use.. So, here is the Onkyo Support Number for you to call, ok?
For Product Support Team Only:
M-F 9am-8pm | Sat-Sun 10am-4pm ET
Posted on Sep 09, 2010
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Posted on Jan 02, 2017
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