[AMRadio] Modulator testing

[Robert Nickels]

On 1/14/2019 9:50 PM, Jim Candela wrote:
>
> Don't even think about floating the scope!! NO!!

Yeah, a tech who worked for me once had a very bad experience floating a 
scope on a test system that was run by an HP-85 instrument 
controller.    Voltage found it's way  to ground alright -  the best 
path turned out to be smack in the middle of the IEEE-488 interface 
module, which not being designed for AC service, proceeded catch fire 
and prompted an interview with the plant fire brigade leader (who I know 
secretly loved being able to discharge an entire extinguisher into our 
cabinet).     The tech did not love having to rebuild it...

However, as Nick pointed out, at 100% modulation the AC voltage from the 
modulator just cancels the DC voltage from the power supply, which 
effectively puts the voltage difference between the primary and 
secondary windings  equal to the power supply voltage.   I've also had 
confirmation from others but wanted to be cautious.

73, Bob W9RAN