Looks like wax, but more probably it is the carrier for the flux used in soldering. Back in the days of old, everyone used a petroleum jelly based, zinc chloride flux for soldering larger wires to terminals.
-Chuck Harris Frank Stellmach wrote: ...
I have seen wax inside very old ww resistors from COHU and KINTEL, on the soldering junction between resistance wire and leads. Obviously to protect the solder from corrosion. Some drops of oil may be used to increase high volt isolation as it ingresses between the windings. I assume, your resistors are tubular ones, with plastiv caps around, and they are not hermetically tight, therefore they cant be filled completely for corrosion protection and thermal conductivity, like in the Vishay metal foil VHP type. Besides electrical measurement (on OHM range!), I 'd recommen optical inspection of the case, and if its possible, of the windings for burnt/overheated areas. Corrosion may be easily identified, also by slightly stained parts of the wire. From your description, the resistors seem to be very old, from the 70ties perhaps, therefore the solder junctions may also be defect, if you find an "open" resistor. Careful resoldering might help. Frank
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