I have a heathkit TC-2 tube checker. It appears that someone had added a wire-wound power resister that I measure to be 75 ohms in series in the "Adjust line control" circuit of the primary side of the transformer. This resister does not appear in any of the schematics that I can find for the TC-2 (or even the TC-1 or TC-3 for that matter). I have another TC-2 tester and this resister is not in that circuit. In my limited understanding, all that I understand is that it is going to drop some of the voltage across this resistor and thus reduce the voltage across the "Adjust line control" rheostat. Thus it is going to vary the the way the rheostat would function. This rheostat is rated at 200 ohm. Can someone please give me some insight as to why one might add such a resistor? And any recommendations about it. Should I remove it or? Thanks