Howard 437A

Steve Harrison ko0u at OS.COM
Sun Jul 11 18:23:28 EDT 1999

At 04:17 PM 1999-07-11 -0400, jackiv at JUNO.COM wrote:
>>... put it (the tx) in the oven at 235 degrees for about 1 to 2 hours.

Most folks get away with this, it seems; but I'd never consider using an
oven as you have very little temperature control and it heats scarce and
hard-to-replace electrolytics, and can cause deformation of the wax-covered
paper forms inside IF transformers. Bits and pieces of insulation or
plastic can and will melt.

Instead, use an incandescent light bulb. Be sure to turn the radio so any
lead holes are facing up so moisture and steam can rise up out of the core.
Easy to do, usually: turn the radio upside down supported on a couple 2x4s
or something with an automobile troublelight or other lamp placed
underneath. Place a piece of aluminum foil on top of the bulb or between
the bulb to to keep radiation heat from burning and heating things, like
electrolytics. Check it every 5 to 10 minutes after first firing it up to
make sure it's not heating something you don't wanted heated. Sometimes, an
old 14-watt Christmas tree light bulb is sufficient. Or, you can use
several of them, each strategically-placed.

Then just leave it for a day or two or more, checking it now and then. The
longer, the better; a week for something that is essentially irreplaceable
isn't too long. Haste truly makes waste when it comes to something like old

This is also the recommended procedure to dry out old transformers, such as
pole pigs. In the case of large pole pigs, you usually leave it with the
lamp something like a week or two; the longer, the better. If the iron core
and windings don't get warm to the touch, they're not being heated enough.
Place a cardboard box over the affair with a small gap at the bottom and
one of the flaps slightly ajar at the top end to allow just a bit of air
circulation, but not enough to let a strong breeze from the outside to blow
inside. Since this is usually done in a garage or basement where humidity
tends to collect near the floor during wet weather, the box is a necessity
or you can wind up getting more moisture inside than was there to start
with. Placing the item on an elevated bench or shelf, off the floor is good.

Afterward, you do NOT want the thing to be cooling down during a storm: it
will absorb moisture from the surrounding high humidity again.

There's another upside to using a lamp in your basement/garage: you only
blow a hundred-watt-hours of energy while doing the "curing" rather than
tieing up the XYL's oven, causing her to blow more money to order pizza or
make cold-cut sandwiches for lunch and/or dinner....

It always takes me ten times as many words to get my point across as anyone
else ever seems to have to say... Sorry!

73, Steve K0XP

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