Audio Systems: Technics SU-V78 stereo problems., impedance load, output impedance

Question
I have a stereo system that for some reason the power to the speakers cuts out
if I turn it up past 2-2 1/2. The guage on the front that shows how loud it is
quits moving and there's no sound at all no matter what I do. If I shut it off
and turn it back on again I get sound again as long as I keep it below 2. What
do I need to do to repair this?


Answer
How many speakers are you using on each channel? What is the impedance of each speaker? How loud are you playing it? What setting is the bass on (example 12 O'olock, 10 O'clock, 3 O'clock)? If you don't know then you can find out by Googling the manufacturer. Providing there is nothing wrong with the unit, this condition is typical for consumer recievers. The output impedance wants to see a similar load (meaning the speaker needs to match the amplifier). A soon as you piggy back (parallel connect) a second speaker to the same channel you lower the impedance load thus increasing the output wattage causing the receiver to overheat. The receiver protects itself by going into thermal protect mode. It must cool down before it will go on again. It could also be a ventilation problem in that the heat is not able to dissipate properly perhaps due to the receiver located in a closed cabinet. If that is the case you need to provide adequite ventilation for the unit. Unless the receiver shuts down at a very low volume with the correct load, I would not think it at all unusual.

If the receiver cuts out when there is a low frequency passage in the music then I would suspect any of the above conditions.