Prusa I3 does not begin to print

Hello fellow printers!

I have a problem with my reprap prusa i3, it simply refuses to print.

I get all the software running, I can control it manually. But when I build a G-code and press start, nothing really happens, the heatbed starts for a short period of time, but never reaches the set temperature.

And for some reason the flat capacitor close to the power supply runs quite hot. (related?)

firmware: marlin
connection program: Repetier-Host v0.90C
I also tried Pronterface

please, does anyone have any answers or help?

The firmware will wait for the bed to come up to temperature before starting. It sound like you are having trouble getting it ti heat up enough. You say the bed heats up to a point. Do you have a temperature reading? It might be a wiring issue. Check the gauge of the wire and the quality of the solder connection.

The "flat" capacitor you mention is actually a resetable fuse. It is normal for it to get hot, but there is a limit at which point it's not a good thing.

I'm trying to get the bed up to temperature manually, but then again, I get a normal reading but stopped heating at 26C or so. while the set temperature was 55C.

and I can't find any bad connections

How cold is your room? The bed should read roughly room temperature with no heating. In most cases that would be 20C or so. If you are only heating up 6 C (to 26) that's not much heat. I would bet that your power supply is not putting out enough power to keep the bed happy. You will need 10 to 12 amps just for the heated bed. You may also have a defective resetable fuse. I would check things with a DVM and see what the voltages look like when it starts heating and after it's stopped heating. That will tell you pretty quickly what's going on. Normally you will have a solid 12V on the bed untill it gets pretty close to the final temperature.