If this is a jd 855,check battery condition/cables as Hal said,also carefully check that battery cable connection on starter sol is clean/tight as this is the common junction for all +12v in tractor wiring,there is a fuseable link in line from starter battery terminal to battery terminal on ign sw & also a fuseable link in line from sol battery terminal to fuse block.
Due to fact you lost everything I would suspect you have a weak/bad battery,dirty/loose cable connections for +/- battery cables or one of the cables bad.
If battery not the problem,check between chassis/eng block with a voltmeter/12v test light to battery terminal on starter sol,battery term on ign sw & main feed side of fuse block,you should get a +12v reading/light at all three of these points with ign sw on off/stop position,if no voltage reading at any of these points disconnect battery cables from battery & check cables with an ohmmeter,one of the cables may be bad.
If you get a voltage reading/light at sol battery terminal but can only get a voltage reading/light at ign sw or fuse block but not both at the same time one of your fuseable links is bad.
When you post questions include mfg of tractor along with model as wheelhorse also made an 855 in the 60's.