Model 152 PSU dummy loads - Re: NeXT Cube - powers on briefly then off again

[Paul Koning]

> On Oct 26, 2015, at 10:56 AM, Paul Koning <paulkoning at comcast.net> wrote:
> 
> 
>> On Oct 26, 2015, at 10:45 AM, Jerry Weiss <jsw at ieee.org> wrote:
>> 
>> Water in the dummy load?      Water cooled - sure.  Water immersed?  ...
> ...
> But for low voltage dummy loads, or for medium power ham transmitters, the voltages involved are not that high.  Plain tap water is slightly conductive, but nowhere near as much as the resistors you're using. 

Come to think of it, water immersed setups have shown up in the literature.  There was a nice article in QST a decade or so ago describing a 1296 MHz kilowatt amplifier, built with a 3CX100A5 converted to water immersion cooling.  The setup included a clever trick to monitor the conductivity of the cooling water, so you could swap it out if it got too conductive.  The water there was in direct contact with the anode, at around 2 kV or so.  Worked fine apparently.

I never built anything like that but the appraoch seemed sensible.

	paul