Just used this an excuse to do a ramps conversion. Stripped down the printer and just kept bare minimum number of wires and re-ran them up top. Have an e3d clone and mount I printed a while back. Already have everything mounted and tested. Just need to do the endstops. I did a print by manually homing and it works great.

I have no intention of going back so it was a way way ticket. So cut wired and added all new connectors etc.

Next would be a heated bed. Truth is I was just waiting for an excuse. Opens up so many doors and learned a lot CD-ROM doing this.

Will post pics once I get it cleaned up.

You will not regret this, I got two of my Jr. converted, my plan is reversible, but I don't want to go back. The print quality is so much better and a lot more options. A little more trouble to fine tune it in the beginning, but once all set, it is very reliable and easy to use afterwards. Not to mention free from trouble to avoid the high cost of xyz filament

I have no intention of going back so it was a way way ticket. So cut wired and added all new connectors etc.

Next would be a heated bed. Truth is I was just waiting for an excuse. Opens up so many doors and learned a lot CD-ROM doing this.

Will post pics once I get it cleaned up.

if your hotend is overheat, check the air way, air direction, and make sure the nozzle and throat is screwed all the way in. Always screw them in while hot with tools, be careful not get your hand burned.

Assuming you did not mod your Jr. in anyway, correct? stock hotend, stock fan, stock software?

First double check if you install the fan in wrong direction after clean a jam. The stock setting is the wind blow towards you, not toward the hot end. Also check if the airway is blocked.

2nd, replace the stock fan with something more powerful, >7500rpm, ideally quieter the stock fan.

Do you know where on the board the fuse is?  Otherwise I will just rewire the fan.