Marantz sr 500 going to "protect" mode when on.

Possible manual, for SR-96 (but doesn't specify SR-96U).

https://www.manualslib.com/manual/1010603/Marantz-Sr-96.html

Possible service manual, that include nameSR-96U)

http://www.vintageshifi.com/repertoire-pdf/pdf/telecharge.php?pdf=Marantz-SR-96-Service-Manual.pdf

It may be weird but it's a small suggestion formerly often occurred at Sony Trinitron TVs building years of 80/90 . maybe the same kind of problem.

A select button internally lingers on the selected matrix usually has priority

Try plugging in headphones, if they work, it sounds like outputs have blown,

marantz SR 4003 how to reset (hard reset ) remove power plug from power .Take cover off locate ic 12 (24 c eeprom) short pin 5 to ground while plugging the power in .Unit will show clear on fl screen .if the unit trips again check channels.

it is not made to drive 4 ohm loads.also if you measure the impedance on the speaker,at some frequencies,it is closer to 3 ohms.This will cause the amplifier to shut down.Today's amplifiers are embellished specs.the old marantz 2325 was 125 watts a channel and weighed 80 pounds.It would eat alive some of the 1000 watt home theater amps of today.Marantz is very nice stuff.

The protection mode is engaged when there's a shor on one of the speakers outputs. This is a major malfunction and, to prevent the rest of the receiver to get fried, the entire system is put in an emergency shutdown mode - the Protection mode.
You must find out if the short is external - in one of the speakers - or internal - in one of the amplifying circuits. For that disconnect every single cable that plugs in the unit and start it .
If the protection mode is still activated then the problem is internal. The only way to identify the faulty circuit is to open the unit and test them all one at a time, starting with the 4 final transistors (2 per channel) - you need a good voltmeter and some basic electronics knowledge. In the worst case scenario the final transistors for both the channels have been shorted - it will cost you about $100 to replace them. Beware, soldering them in place is a delicate job, use grounding precautions and don't overheat them.
If the protection mode is gone then one of the speakers has failed. Either replace both of them or take them to a specialized repair shop, you can't fix speakers at home.

Not having the ability to look at it on the bench, more than likely your DSP chip is bad. If you have a local repair house that is willing to confirm that is the problem without charging you an arm and a leg, that's your best bet. It is an expensive repair, anywhere between 300 to 500. At that point, I would say to replace the unit. Sorry for the bad news, but that's my "best guess" The only other thing to check would be your "Audio input Settings" Make sure it's either on "Auto" or whichever type you are using. "Digital Coaxial", "Optical", or "Analog" (RCA) hope this helps! If you have any further questions, just post a reply and I can help further. Best of luck!

Sounds like it's in protection mode. Take it to a hifi shop, they should be able to reset it.

I have a POW 5 failure on a marantz sr 7500. Anybody know how to fix?