02-13-2011, 12:04 AM
The issue of sealing transformers and other components like mentioned above was a sort of policy in the early days of radio. Soft waxes were good, and reasonably permanent when the sets were built. Just keep in mind that the life of a radio was probably 5 years, so permanence was never a factor of consideration. Could you ever believe that any of the good radio companies could expect one of their radios to be in service 60+ years from manufacture?
Today, good practice in transformer manufacture dictates that the transformer is double vacuum dipped in insulating varnish, and baked for final finishing. The vacuum dipping causes the varnish to penetrate into the windings and interlayers of the transformer. The vacuum during the varnish dip draws any air bubbles out of the winding, prior to the baking operation.
In the early days, it's doubtful that any sealer of any sort was used in a transformer. The windings were done as tightly as possible, then the whole thing was potted with tar, which sealed the windings......reasonably. But, with operation, especially over a few years, the turns, especially in the finer gage of windings would vibrate within the winding, and often chafe against each other, then develop a short between turns. One shorted turn in any transformer means the beginning of the end. Heating builds up, and the transformer is a goner.
We have heard of certain sets where power transformer burnouts were chronic. The big RCA Radiola amplifiers of 1928-29 were one good example. By 1934, the power transformers burned up. If one dissects one of those transfomers, it appears that tar was totally depended on to seal the transformer. Not good practice.
A few years back, a restorer from this area commented that he didn't recall having a Philco power transformer burn up on him. Pondering on it, I never have, either. Part of the answer is that Philco used huskier transforemers than other companies, while certain other companies (Brand "Z", for example), used marginally rated power transformers, and have a high burnout rate.
But, where output transformers don't see heavy power loads, waxes were safe to use for sealing, so you might have wax coming out, if there is a shorted tube or capacitor across the primary. Wax was also seen in filter chokes.
Today, good practice in transformer manufacture dictates that the transformer is double vacuum dipped in insulating varnish, and baked for final finishing. The vacuum dipping causes the varnish to penetrate into the windings and interlayers of the transformer. The vacuum during the varnish dip draws any air bubbles out of the winding, prior to the baking operation.
In the early days, it's doubtful that any sealer of any sort was used in a transformer. The windings were done as tightly as possible, then the whole thing was potted with tar, which sealed the windings......reasonably. But, with operation, especially over a few years, the turns, especially in the finer gage of windings would vibrate within the winding, and often chafe against each other, then develop a short between turns. One shorted turn in any transformer means the beginning of the end. Heating builds up, and the transformer is a goner.
We have heard of certain sets where power transformer burnouts were chronic. The big RCA Radiola amplifiers of 1928-29 were one good example. By 1934, the power transformers burned up. If one dissects one of those transfomers, it appears that tar was totally depended on to seal the transformer. Not good practice.
A few years back, a restorer from this area commented that he didn't recall having a Philco power transformer burn up on him. Pondering on it, I never have, either. Part of the answer is that Philco used huskier transforemers than other companies, while certain other companies (Brand "Z", for example), used marginally rated power transformers, and have a high burnout rate.
But, where output transformers don't see heavy power loads, waxes were safe to use for sealing, so you might have wax coming out, if there is a shorted tube or capacitor across the primary. Wax was also seen in filter chokes.
