[R-1051] R-1051 Power Transformer Issues

[paul swed]

Thank you for sharing

On Sun, Feb 7, 2010 at 3:52 PM, Geoff Fors <geoff at wb6nvh.com> wrote:

> A couple of people have e-mailed me off-list asking about the R-1051 power
> transformer issues and the repair process.
>
> First, I only have experience on the "B" models and the original problem
> may
> only track to only one transformer manufacturer.
>
> The problem begins with intermittent fuse blowing.  Eventually the fuse
> blows constantly.  I was lucky the first time I ran across this and saw a
> small arc at the base of one of the high voltage secondary terminals, right
> before the fuse blew.  Investigation showed that what happened was that the
> black rubber shim/washer between the porcelain insulator and the case had
> become conductive and was causing an arc to the case. Maybe those 1940's
> transformers with cork insulators aren't so old-fashioned after all?  I
> have
> seen this with the gray "rubber" insulating washers used by Hewlett Packard
> in a number of their 1990's vintage computer monitors, where that material
> also became conductive with age.
>
> The repair for this is to remove the wiring from the terminal and then the
> insulator, which, because of the terminal design, requires destroying the
> insulator.  I used a pair of small vise grips to shatter them, and then I
> removed all trace of the rubber washer below with a dental pick.  I then
> took a plastic drinking straw and cut off a piece about the same length as
> the original insulator and slid it down over the terminal until it
> contacted
> the case.  I filled it with a mixture of J-B weld epoxy and waited a day,
> then removed the straw piece with the help of an X-acto knife.  The wires
> were then carefully resoldered to the terminal, being careful not to melt
> the J-B weld.  This should restore things to normal.  The same trick has
> been applied to Hammarlund SP-600 power transformers.  Note that in the
> 1051, the lower voltage terminals do not provide enough potential to break
> down the washer (so far!) so you can leave those alone.
>
> Geoff
> WB6NVH
>
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