[volt-nuts] Wanted wirewound precision resistors and ESI DB877

[Chuck Harris]

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