I just finished restoring a model 70. The original output transformer was bad. When I removed the tranformer (still riveted to the speaker pan) I found it was filled with PARAFFIN WAX! Not only that, but some of it had obviously melted and leaked out into the tuning capacitor and onto the chassis top. It was VERY difficult to remove. I had to melt it with a heat gun and wipe it off the best I could. Normal solvents seemed not to have any significant affect on the thick wax.
I don't see how anyone could have actually ADDED the wax inside the transformer! It was still riveted to the speaker pan. Has anyone seen this before in another radio? If it was original, why? Moisture?
Hello, Dave: I think Ron would have the definitive answer for this, but seems like wax was used for many components including transformers in many of the sets I have.
Most likely, it was an attempt to prevent moisture absorption. Which, as we know with the bakelite block caps and the brown paper caps, didn't really work as intended.
I don't think I've ever seen a Philco audio output transformer leak wax before. The primary must have developed a major problem for that to happen.
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.
Ron Ramirez Wrote:Most likely, it was an attempt to prevent moisture absorption. Which, as we know with the bakelite block caps and the brown paper caps, didn't really work as intended.
I don't think I've ever seen a Philco audio output transformer leak wax before. The primary must have developed a major problem for that to happen.
The output transformer was open. But there were no shorted or badly leaky capacitors (the radio worked once the output transformer was replaced). Likely it was a gassy 47 output tube (that tube was not original) - looks like it took awhile for the transformer to fail. The radio was eventually recapped after cleanup. It just seemed weird to me that Philco would have used clear pareffin wax rather than tar for potting.
I expect they used whatever the refineries down at Marcus Hook were producing, but maybe all they could get at some particular time was paraffin. You can't shut down for a minor problem like that; the purchasing agent gets on the phone and finds something that will do, even if it costs more.
Quote:I don't think I've ever seen a Philco audio output transformer leak wax before. The primary must have developed a major problem for that to happen.
i recently restored a philco 42-380 and had the some problem i got rid of the thick wax by using a lighter and it worked fine. wasn't this wax used to seal the transformer?
I doubt if they used paraffin wax to seal a transformer, the melting temperature is too low and paraffin wax is too brittle, more then likely it's some sort of organic wax like bees wax or whatever they sealed paper capacitors with back in the day.
Best Regards
Arran