[R-390] thanks

[Richard Loken]

On Sun, 26 Jul 2009, Natan Huffman wrote:

> I want to thank all who had ideas about the nasty hum I had on my 1967 EAC.
> The problem was in the line filter, so I'll replace it and all should be
> well.  The give away was the 60 volts on the chassis!

Oh no, the filter debate again.  I prefer the black goo and BBOD threads.

Yes the there is 60V on the chassis and if you plugged it into a GFI outlet
then the GFI would trip.  However, the filter and the GFI are both working
as designed and the R390 manual tells you not to operate the receiver
without a proper ground (the implied reason being that the avarage
operator gets tired of being whacked by 60V every time he touchs the radio).

Not that it applies to the R390 but 60V at what load?  Take any device with
a line filter (made by Corcom or Thomas Edison himself, it makes no
difference) remove the 3rd prong ground from the chassis and measure from
the chassis to ground and you will read X volts AC.  Connect a resistor
between the chassis and ground and measure the leakage voltage again and
the reading should be lower.

Again, ignoring the R390 and its outrageous capacitive leakage current to
the chassis, but looking at more sensible appliances with their expecation
of being handled and mishandled by the general population... Hmmm.  Lessee,
If I put a 1,000 ohm resistor on there and I still read (number picked out
of the air) 10 volts then I would be leaking 10mA to ground - now I am going
to get interested and so should any functional GFI since, AFAIR, a GFI
should trip at 5mA.  Have I got that wrong?

-- 
   Richard Loken VE6BSV, Unix System Administrator : "Anybody can be a father
   Athabasca University                            :  but you have to earn
   Athabasca, Alberta Canada                       :  the title of 'daddy'"
   ** richardlo at admin.athabascau.ca **             :  - Lynn Johnston