Sony STR-DE315 will not power up

Check and replace damaged component/s at its horizontal scan output section circuit. Check the LOT (Line Output Transformer) too for damage. Replace the horizontal scan output transistor. Check the input voltage to LOT. If the voltage is absent check the feeder resistor; if any. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts.
http://electronicshelponline.blogspot.com/
Type in the brand name of your device, in the search box [at the top right] of the display window and the Search will start at once as you type in, and will show you all the related posts. It will make surf easy.

no front panel display means one of twot hings: either the power transformer is blown, or the main power fuse. If the main power fuse is blown, then there are likely to be shorted output transistors that will need to be replaced.

Doubt the main pcb needs replacing, but the standby transformer would definitely go in that situation. Standby transformer wouldn't be that expensive, but no way to say that it's the only thing that is bad. It is also soldered in, so you would need to know how to do that to replace it, or bring it to someone who could. If you're staying long-term in Europe, it might just be better to buy something local so as to not run into this problem again.

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 power supply is bad. Check for open fuses. If fuses are good, then the voltage regulator in the power supply may have damaged.

It could! Most of the newer receivers these days need alot of ventaltion!
Unless its being played to loud with to many speakers connected!

Does it still do this if the speaker wires are disconnected? The amp is protecting itself from a short on the output. maybe yo have a dead or distorted driver in one of the speakers. Also there could be a defect in on of the amp circuits.

yes primary smoothing capacitors it place just after the rectifires.

its on your front speakers there suposed to be a towers

You probably have shorted rectifiers and/or transistor(s) on standby board. Trouble-shoot rect bridge and cap. Feel stand by circuit transformer for abnormal heat, sure sign