Tradsteve, if your Telecaster is in good shape it should be one of the least feedback-prone guitars out there. But the old single coil pickups they installed on those have been known to go microphonic -- which basically means that the wiring and/or coil windings have loosened up, and are transmitting vibrations and sound that is unrelated to the musical notes being played. This is a harsh, unmusical, squealing feedback, not to be confused with the singing/sustaining feedback that is considered a desirable part of an electric guitar's sound. The pickups can be repaired (re-sealed) or replaced to deal with this -- repair them if you love the pickups or want to preserve the "original vintage" character of the instrument, otherwise replacement is probably easier and offers a more certain outcome. I would encourage you to do one or the other -- a 1950's Telecaster is worth keeping in good shape.