I have a yamaha RXSL100 receiver and when I turn on it shuts off

Could be simple, or you need to replace.

First the simple:
Check your speaker wire connections on the back. People tend to strip way too much of the insulation from the wire leaving exposed copper that may touch and short out against each other.

Here is a simple test.
Document how your speakers are connected paying attention to polarity. Make a chart, label with tape - whatever works for you - then disconnect all speaker wires.

Then do the same for any other connected wires.

With everything disconnected from the back of the receiver, turn it on again. If it stays on, then you probably had speaker wires shorted.

Reconnect all cables again, except the speaker wires and turn the unit on again. It should stay on.

Finally, reconnect the speakers, one pair at a time - being mindful to connect the bare ends cleanly onto the speaker terminal and that there are no stray strands that may touch anything. Turn the receiver on.

Repeat this will all speakers are connected. Your receiver should be find.

It is shutting off to protect itself because of a short on the speaker wire.

OR

It could have been damaged because of a short, or from lightning or you are hard of hearing and really like to crank it up - causing internal damage.

If so, you may need a new receiver.

Good luck!

Unit is in protect mode. Sometimes an ipod draws too much current through the usb jack and causes the unit to shut down due to an abnormal voltage being detectected. Press and hold the 'info' and 'tone control' buttons and push power. This should turn the unit on. Turn it back off and turn it on again and should power up normally. If the ipod continues to make the unit shut down when plugged in, try and make sure it is fully charged before plugging it into the receiver - this may help.

A capacitor problem or overheat problem.

my Yamaha rxz1000 will turn off byitself

Does it work without PS3 attached?
When receiver turns off, it is usually due to badly connected/configured speakers. Try powering on the receiver without speakers.

Your unit have had detected a fault and enter the protect mode. To determined, what exactly wrong with it, you will have to take it to Yamaha authorized repair facility.

Try to disconnect speakers one by one and see if any of them causes the problem.

THE SPEAKER WIRES ARE REVERSED.... On the receiver the red side is always positive and black is always negative.
change + to - or
change - to + on one or more speakers.
positive side--------------------negative side
red --------------------------------black wire
gold wirew/silver--------------silver wirew/gold
white lined----------------------non-white lined

Get another receiver! I had the same problem and had the power supply replaced $250 and after 3 months it started doing the same thing.  I just purchased a Pinoeer Elite VSX 90TXV.

Modern home-theater components monitor themselves electronically for potentially dangerous malfunctions such as damaged internal parts. When a unit's microprocessor senses a problem, it will typically shut down so that no further damage -- or potentially dangerous disasters like fire! -- occurs. Your receiver is identifying something upon turn-on and shutting down as a result. My guess is that you're going to need service for your Yamaha. There's likely no fix that you're going to find. You need a professional service technician.