The poweramp of my Marantz SR6004 AV Surrount Receiver only turns on after about 3 minutes.

On the SR6004 the factory reset is accomplished by holding the Surround Mode + Clear buttons for 3 seconds. You may need to check the last page of the troubleshooting section in your manual if your model is different.

Reset to factory and make sure you have a good network wifi signal before starting a firmware upgrade. The reset is listed on the last page of the troubleshooting section of the manual. (Surround + Clear for 3 Seconds on my SR6004)

If the red led is blinking fast (8x/second) the power supply is likely damaged and the unit will need to be serviced. If blinking slow, the most likely cause would be a shorted speaker connection. To help find the cause, unplug everything including the power and speakers. Connect only the power and try to turn the unit on. If the light doesn't blink, you know you have a shorted connection. Power off and connect the inputs and then power back on. If the light is not blinking, you know the problem is with an output connection. Just find the bad connection by process of elimination.

Manual: http://us.marantz.com/DocumentMaster/US/SR6004-5004_U_EN.pdf

Buy a headphone 3.5 mm jack to RCA converter and plug it into aux jack

It almost sound like your player is on a standby mode or something if you turn it on and it turns off. You turn it back on and it stays on is because when you think you turning it on, it was actually turning it off. Sound kooky but that's what it looks like to me.

It sounds like you've read one of my many posts on 901 deployment in the AV world.

Functionally, what is the difference between one amp with 'x' channels or 'x' mono amps? Nothing. Pre-outs don't know or care what else an external amp does.

According to this link http://www.ecoustics.com/electronics/products/new/642968.html those amps are 2- and 5-channel, respectively.

There was a time when I had two bridged-mono Carver Cube atmps (at a real 400 watts) pushing one 901 each but that was big time overkill.

I now use a Carver AV-406 (functionally the same as your MM7055) with the 901 EQ in between the AV Receiver's front pre-outs and two 110-watt channels. Other channels on the AV-406 pull subwoofer and surround back duties. My AVR directly powers only the center and surround speakers.

The MM7025 would work for you.

Hi,
There are two circumstances that I know of that a properly installed unit such as your Marantz would shut down. So here is the Theory and Data I know of.
A Your receiver has a great deal of amplification power. If it is in a closed cabinet without excellent ventilation, it will shut down if used at high volumes because because over heating. Because of it's very high power, when played loudly, it generates excessive heat.
When watching certain movies the BD player may be over-driving the limits of the amplifier section of your receiver. Page 78 of your owner's manual addresses this. Here is a link to download the manual from Marantz.
http://us.marantz.com/us/Support/Pages/Manuals.aspx
B There is one other very important thing I should mention to you. When people use high powered equipment and initially turn up the sound. After a short time, the mind turns it down. What next happens is the reason professional musicians and sound engineers often have permanent hearing loss after a relatively short time.
What tends to happen is that the listener and often the engineer running the sound mixing board at a concert(after a certain period of time) believes the sound is not loud enough when it really IS loud enough. (this tricks the audience as well) and engineer turns it up. After turning it up, his mind (and the audiences') turns it down mentally and they again think and agree that it not loud enough and then again, the volume level is turned up. And up. And up. The only reason I'm not deaf is that I discovered this when I was building sound systems as a kid. I also studied about it. So please be careful when you play things loud. Permanent hearing loss starts to occur at the very high frequencies and rolls down from there over a period of time. Hearing loss can start to occur in just a few hours at 110 decibels. permenant hearing loss is exactly just that. Permenant! It just doesn't come back. If you use this information, you will enjoy hearing music for the rest of your life.
I hope this helps,
Best Regards,
Mark

Having looked at the manual it makes no mention of connecting a record player. So I think we can assume that there is no built in pre-amp for a magnetic cartridge. So you will need a pre-amp for that. You can use any RCA sockets on the device that are Left and Right audio in. A tape or CD player one will do the job, as long as they are analogue inputs.

The most common problem found on FixYa for Audio Video Receiver's is:

My receiver say's "Protect" or turns on then off. What's wrong? Seven times out of ten it is a shorted speaker or speaker wire. To determine your exact problem, the first step is to disconnect all speaker wires "at your receiver" Next: Turn the receiver back on. If your receiver still says "protect" or turns off, it needs to be serviced. If your receiver stays on; reconnect your speakers one at a time and power back up after each speaker. You may find that after reconnecting all speaker wires it works! Most commonly the small braids of wire from the + to the - have touched and have caused the problem. In some instances, you noticed the problem only when turning the volume up. either way, make sure the exposed wires to your receiver are no longer than 1/2" long and are completely under the screw down terminal or slide in. When you've found the wire or speaker with the problem, your receiver will go back into "protect" At this point, disconnect the wire from the speaker at the speaker that may be causing the problem then test again.* Note* Make sure speaker wires do Not touch each other as this Will cause a short! If you turn the receiver back on and it stays on, you now know the problem is in your speaker itself. To test your speaker, you will need a multimeter. Set it to ohms resistance and touch the speaker terminals, if there is a short internally the meter will read "1......" If it's an analog meter, it will peg to the right. There's your problem. Now, within any speaker there are quite a few possibilities as to what could be causing the problem. Most common is a blown coil and the speaker needs to be replaced. Some speakers have internal crossovers (usually floor standing speakers) and may have a shorted or burnt board (usually very visible brown burn marks on the board) and can possibly be repaired if your handy with a soldering iron. Now, if you disconnect the speaker wire at the speaker and it still says "protect" Check your wire for the obvious cut or nail thru the wire if possible. If your system has wiring that runs behind walls, you may need to use your meter again. Disconnect the wire at both ends, keep the ends separated, put your meter on ohms resistance and touch probes to the + and - wires at one side. If the meter pegs to the right or reads "1...." the wire is shorted and needs to be replaced or repaired at the short. Hope this helps.

to turn on , press and hold down surround mode,exit and clear buttons for more then 3 seconds,system should reset. if it goes back to a flashing power light you will have shorted output transistors inside your receiver.