Richardson's handbook of projection (1930)

1344 HANDBOOK OF PROJECTION FOR If the wire test shows a reading, then the ground is between its upper end and the terminal in the transformer compartment, assuming of course that you have disconnected the wire in the compartment before testing. Should you be unable to locate the fault, or should it lie in conduit or BX and there is not time to locate and repair it, you may effect temporary repair by connecting an insulated wire between lug No. 7 and the terminal in the transformer, disconnecting the old wiring, of course. No evil will result except that you may, and most likely will, pick up more or less noise from other circuits. To minimize or even possibly eliminate this, use shielded wire if you have or can get it, grounding the shielding, but remembering that the ground connection must be a thorough one. A poor or loose connection to ground will set up more noise than the well grounded shielding would eliminate. In case no shielded wire is available, then use a twisted pair of wires, connecting one of the pair to supplant the disconnected faulty wire and the other to ground. In fact it is well in such a case to ground both ends of the ground wire. In some cases grounding one end of the wire will seem to be of slight assistance in noise elimination, whereas by disconnecting that end and grounding the other end all noise will cease. It is a queer and rather tricky proposition. CONDENSER NOISE ELIMINATION.— If a con denser is at hand, it may be utilized to eliminate noise in the before described connection. A micro-farad is excellent for the purpose. Connect one of its terminals to the No. 7 lug at top of amplifier and its other terminal to ground; also ground the condenser container itself.