[AMRadio] Re: RE:Insulating tranformers, chokes, etc.

[Jay Bromley]

Hi Don and AM gang,

A few days ago I think you were asking what was wrong with using rubber
mounts to insulate old modulating iron, chokes, and plate transformers, etc?
I wanted to comment on this a few days ago, so please forgive the delay.

A few years ago I was working on a Kenwood TL-922a and I had the high
voltage crowbar broken with one of those rubber feet that are about an inch
thick.  I have done this a million times before on some old Heathkit SB-220
amplifiers with no problems

To make a long story short, it caught on fire with me right there working on
the amp.  It was a very dicey deal getting the amp turned off,  putting out
the fire, making sure there still wasn't any high voltage left.  At first I
thought the rubber foot I had used had an internal washer that was arced to
that started the fire.  I checked this by cutting the remaining part in
half, but none was found.  Apparently some rubber has much better dialectic
properties than others.

In summary, I don't think I would ever use rubber for a high voltage
insulator.  I do think using ceramic insulators to insulate one's high
voltage components would be OK.

I can't help thinking if this would have been a remote transmitter with a
rubber fire and some of the safety fuses/breakers were to fail at the same
time.  The result could be disastrous!

Even with my little old rubber foot that flamed out the mess was very hard
to clean up.

hI once set a bicycle tire on fire with RF, but I will save that story for
another time!

I would use only ceramics or none at all.

Like the old QSTs used to say------Beware!

73 de jay/w5jay..