[R-1051] R-1051 Power Transformer Issues

[Geoff Fors]

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