What are the power source requirements for a DeWalt #756 Grinder?

It should be on the sticker with the model number & other information, if not it's likely on your receipt or original box. I know if you're like me you have no clue where they are, check the area where the battery connects to it also, if no luck just call/email DeWalt or call your Local Lowe's and get a Tool SalesPerson on the line, they'll tell you! I just had the same issue with some Milwaukee Tools that needed warranty repair, I know this is frustrating.

https://www.weeklytools.com/different-uses-for-an-angle-grinder/

An angle grinder is a multifaced handheld power tools that was invented by a German company. We may don't know a lot about this tool because it is an unrecognized instrument like some other tools. Now we will discuss different Uses for angle grinder.
An angle grinder is also known as a side grinder or disc grinder. It is a machine with a rotating abrasive cutting disc. Angle grinders can be powered by an electric motor, petrol engine, or compressed air. It comes in a wide variety of different sizes and powerful motor, each with the other purpose. Once anyone knows about these, he can easily find out the best angle grinder for his needs. Angle grinders are quality fulled equipment for any metal fabrication shop, and those are typically used in auto repair, workshops, and construction sites.

https://www.weeklytools.com/dewalt-angle-grinder-buying-guide/
When it comes to Angle Grinder, the name of the Dewalt tools maker comes first. We will look at the basic parts and functions of a grinder before purchasing a machine. Then let's see the details without delay.

The 735 draws 15 amps, which is the rating of typical lighting circuits in homes. The receptical in the wall is sometimes 15 amps although those circuits usually have 20 amp breakers. Since you said "fuse", it might be a bad fuse or even the wiring between the two. Circuit breakers go bad also. If you can confirm the receptical supplies voltage, it is time to check the 735.

Unknown if the device has a termal switch inside. I doubt it would go bad, but you implied a resting period allowed it to run several more times after the fuse in the basement was replaced. If it reset once, it should do it again. If you can find a diagram, there might be a fuse inside, but someone would have to take it apart to check.

A motor can get so hot that a solder joint inside can let loose and it will never run again. Sometimes the coil (windings of the motor) can short out (melt together) and this will increase how much current goes through it and also generate more heat and melt more windings together. Besides producing a smell, your house fuse would burn out real quick.

I had a chuckle over your 2nd sentence but I dare not say why. If it started after you came out (of the house), why did you not run it for a longer time?

A motor requires more power at the instant of turn on. 15 amps of running current will require 20 amps or more when starting. "slow blow" fuses (vs quick action) and circuit breakers can deal with the short period over current requirements.

it would be much better if you bought a new one because it would be cheaper

http://www.searspartsdirect.com/partsdirect/user-manuals/DW756TYPE1-Dewalt-Parts-BENCH+GRINDER-manual

The link should connect to the manual for DW 756. If the link does not work, go to the Sears parts web page and look up the grinder.

Check your power cord. Turn the grinder on, then pull and twist the power cord, especially by the boot coming out of the grinder. If there's a break in the line, it's possible for it to work in some positions but it will die if you change the orientation of the cord to the tool.

On top of the head there is a button to press to lock the blade arbor. Press it down and turn the blade by hand until it locks in place. Then you need either a spanner wrench or nut wrench depending on which arbor nut you have. Grinders usually come with whichever wrench they need. Most grinders have an arbor nut with two or four holes and require a spanner wrench with two studs that fit into two of the holes to remove the arbor nut. Some have an arbor nut with a hex fitting, like a regular nut & bot setup, that the arbor wrench fits on. If you don't have the proper wrench sometimes you can get the arbor nut off with a pair of vice grips or pliers. You will want to turn the nut in the same direction as the blade spins when the grinder is on to remove it. When you put the new blade on, get the arbor nut hand tight, it is self tightening and will get tighter as you use the grinder.

I need a 4CR-20-756 Klixon relay for a bench grinder.

Hello, W/D here.

It's always a wiser choice to leave the guard on to help keep particles from being slung at you.
In addition to the guard, you should also wear eye protection. I have extensive experience in industrial work, and I cannot emphasize strongly enough how important this is. Where I worked, working with a wire wheel required that the guard be in place and that the operator wear safety glasses and a face shield. An eye injury is one of the most serious accidents that can be easily avoided.
Best regards, and work safely, --W/D--