WS19 cable

[Johnny Canuck]

Lead, Lead/Tin or Tin solder always requires a flux or rosin or a destructive amount of heat for removal.
Use plenty of rosin brushed onto the old solder, add extra rosin if the heat doesn't transfer almost immediately, should melt quickly. Don't use flux(plumbing) as it contains acid which is corrosive with predictable results.
Old solder can be reused, it is metal, doesn't deteriorate with time, flux and rosin are the key, don't use it and all you'll get is grief.
The oxidation on the surface of the lead/tin insulates the solder from the heat of the iron. Flux and rosin cleans the corrosion allowing the heat to transfer.

Geoff