[ARC5] Slightly OT: Transformers

[hwhall at compuserve.com]

>
If there is suspected moisture ingress some folks have turned to a 
low temp bake in the oven for several hours (when the XYL is out of the 
house).? Another idea is to put enough DC current into an inner winding to 
warm up the transformer from the inside for several hours. 
>

I recently worked on several old transformers recently and put them back to work. I thought about heating internally as mentioned but didn't have that large a DC supply on hand. Instead, I put each into a box (cardboard box will do, even) along with a dropcord light (aka trouble light) with a 40 or 60 watt buld as a makeshift oven & poked a long thermometer into the box. For the smaller chassis, I just put the whole chassis in.

The temp can be controlled by running the bulb off a variac or dimmer (best) or even by fiddling with the size of one or two holes in the box. I was able to reach temps of 120 - 150 deg F easily. Check the temp periodically to ensure it hasn't drifted too low or too high. If doing this in a really cold garage, additional insulation may be required, perhaps old towels draped over the box. I suppose that if you live in a high humidity area, putting some silica gel in the box will help dry the xfmr out better. This keeps you out of trouble with the wife and her kitchen oven.

Wayne
WB4OGM