Onkyo TX-SR508 cooling fan

Amazon com Receiver or amplifier cooling fans with thermoswitch multi...

most cooling fans in receivers only come on when they are needed. Some turn on at higher volume levels, others will not turn on until the unit gets too hot.

Get a RCA cable and connect from your amp where it said Sub Woofer in the Pre Out box in the back of the amplifier top left hand side and take it to the "Sub In" located in the back of your Sub woofer bottom right hand (White round connector).
Good Luck!

You have this all backwards. So essentially it won't power on. THAT must happen before setup or anything else.

http://www.retrevo.com/support/Onkyo-TX-SR605-Receivers-manual/id/2526bh742/t/2/

Generally speaking, an amp attempts to protect itself from heat, shorts, overloads and operator exuberance by refusing to turn on or stay on.

Overloads can be from excessive periods of high output or marginally low impedance loading by the speakers; and shorts would be wiring issues or a speaker blowing up.

You should be able to feel if it's hot. WHY is it overheating? Make sure it has sufficient ventilation on all sides and that vent holes are not blocked by dust balls. Ensure the fan (if equipped) is running as designed (some only operate on demand). Clean dust and debris from it.

If the amp comes back on after cooling, you're lucky. They only have so many self-protection cycles in their lives so continuously resetting or cycling their power without addressing the cause can do more harm than good.

If it protects immediately on a cool power up you should disconnect the speaker connections and try it 'nekkid'. If it comes up then diagnose which lead(s) are shorted. If it does not come up the problem is internal and should be left to an experienced and competent hands-on tech.

The reason you are not getting a good picture is because of the HDMI interlink cable. Make sure that the HDMI cables you have bought are at least version 1.3a. May be one of the cables is v1.3a that is why you are getting OK picture when you connect the projector directly ( it might be an expensive cable ) . If you do not get v1.3 you may also buy v1.4 which is 3D ready.
The poor band width of the cable must be giving you a bad picture.
Now if both your cables are OK and you are still getting a bad picture you have faulty HDMI pass through circuit on your TX-SR508.

Does it have a cooling fan? if it does, then check its actually working. Protecton circuit maybe cutting in.

Is OSD set to ON? See below

Set the OSD (onscreen display) mode before you start using the RI Dock. 1. Plug in the AC adapter. 2. Turn on your TV and amp, and select the appropriate inputs on your TV and amp. 3. Insert your iPod into the RI Dock. 4. Select the video output mode depending on the video connection. While pressing the remote controller's [SETUP] button, press the Up [ ] button for the component video connection, press the [ ] button for the composite (default) connection. 5. Use the remote controller's [MODE] button to set the OSD mode. On: Playlists (artists, albums, songs, and so on) are displayed on your TV, and you can navigate and select your music or video while looking at your TV. While this mode is selected, your iPod displays the Onkyo logo. Off: Nothing is displayed on your TV and you navigate and select your contents by using your iPod's display.

Do you mean TX-SR508? The following should work even if that is not the exact model.

The LS25 supports ONLY analog stereo audio input and the speakers themselves are NOT desigend to be driven by anything BUT the LS25 electronics.

If you still want to use the LS25 as speakers just run an RCA cable pair from VCR / DVR Out on the Onkyo to the AUX IN on the LS25 Music Center.

http://www.retrevo.com/support/Onkyo-TX-SR508-Receivers-manual/id/23653ag910/t/2/

http://www.retrevo.com/support/Bose-Lifestyle-25-Series-I-Home-Theater-Systems-manual/id/525ag019/t/2/

tou may want to hook this to speaker select switch

I have the same receiver and the way to fix is simple. in the main board of this unit there are 5 connectors and they slide into other components like Lego. the issue is the king of material they are made of it's cheap. if you reseat the mainboard it will fix it for a day or two, them it will start again. the easyway is to re seat the board and put a fan inside of the receiver between the transformer and the inside of the amp pointing down about 20 degrees connect the fan to a ajustible voltage adapter and connect it to the outlet in the back of the unit. so it comes on when you turn it on. this voltage adapter is cheap. the adapters people buy for phones and or MP3's at Radio shack or Best buy it goes from 1.5v to 12 volts/ this way you can control how loud the fan is in side the receiver. i find 4.5V does the trick. The connectors on this board start to loose contact with some of the pins when heated. the fan keeps it cool enouth to fix the issue. I fixed manny these ONKYO 804's this will fix it. you just have to do it. the main board is inder the HDMI board in a Vertical position running from one side to almost the Power supply. it has 2 screws also holding it in the inside middle back of the amp. Becarefull with these amps 75 V at 23amp's DC is no joje leave it off for a couple of hours to satart working on it. Good luck.