[R-390] Isolation Transformers, GCFI and Balanced Power

[Ken Harpur]

Hi Roy,

Thanks for your response and for the info...

> One common way to overcome the trouble is to remove the original filter, and make a plate that will hold a  modern line filter nicely in the space.  (Do not hope to buy a Greenlee punch that makes the hole - they are priced at over $400.00)  Then use the common computer style line cords.  (Are they the same in NZ?)

Yes I had thought about doing that and had looked at the Corcom line of filters to try and adapt nicely to the radios. The computer line cords are the same in NZ and Australia where I am currently living. I don't have the necessary metalworking tools to create a nice professional-looking job so my thoughts turned to rebuilding the originals. I realise it will be a messy job but once it's done, it's done. 

All my equipment is grounded via the power cables with the three-prong plugs. My current set-up is temporary because I will be moving back to New Zealand in the next year or two. I haven't installed a decent (RF) ground system here I'm just relying on the safety ground through the mains...I wouldn't dare run a R-390A without grounding the chassis.

> Isn’t there a switch on the power supply you move?  ‘Can’t remember.

On the 390 yes, on the 390A  you have to re-wire the terminal strip on the power transformer...

> One possibility is to use a voltage regulating transformer - common name “Sola”, but made also by other companies.  Normally these things have an isolated secondary, though if there’s a three wire grounded outlet socket, the safety ground will likely be connected through to the case and the ground on the supply cord.

Yes I have heard of Sola, very interesting. Only thing that would concern me is the current draw even at no-load and the heat. Although maybe that is a good thing...I play radio the most during the winter months so the heat could be beneficial! It would be nice to find something that would fit inside a rack case and have a double pole switch to completely shut off the mains when not in use.
I've been looking at Plitron transformers, their units look very well made. They're not cheap but in this world of mass-produced junk I'd rather pay more for quality...

> One further note:  The Sola brand transformers are guaranteed for 10 years.  In a world full of 90 day guarantees, this means that the company thinks they almost never fail.  In practical use, they really do almost never fail.  So if you see one at a hamfest that looks really old and the price is modest, go for it.
> 
> An UNtested possibility:  If your sola device puts out modern line voltage, it MAY be possible to add a few-turn winding onto the thing to be wired in voltage opposition to the output connection.  This will make it into a line bucking voltage regulating isolation shack warming device.  

Haha...yes indeed, "line bucking voltage regulating isolation shack warming device" has quite a nice ring to it. I'm already partially there, I do in fact use a line bucking transformer, configured as an auto-transformer to get my line voltage from 240V down to 230V. It works very well but sadly it doesn't run warm enough to heat the shack!

Regards,
Ken