[Collins] INFO PLEASE

[Dr. Gerald N. Johnson]

On Thu, 2009-06-18 at 21:54 -0500, Bob McGraw - K4TAX wrote:
> One approach that I've used is to connect my sinewave audio generator set at 
> 60 Hz to a winding, adjust the level for 1 volt RMS generator output and 
> then read the voltage on the other windings.  Makes for easy calculations 
> and takes a lot of guess work out of figuring a transformer turns ratio. 
> Also keeps the "unknown" voltage on the windings from biting too much should 
> you accidentally get across them.
> 
> 
> 73
> Bob, K4TAX
> Sparta, TN

I've liked twelve volts because that makes every test voltage down by a
factor of 10 and I don't have to read millivolts on the low voltage
windings. Yet a typical b+ winding (not the transmitter high voltage)
has only 30 or 40 volts red to center tap which doesn't hurt too much.
Using 1.2 instead of 1 for your setup would make the line operated
voltages a simpler factor of 100 instead of 120. But a 2.5 volt filament
winding would only show 25 millivolts which is off scale on some meters,
especially analog meters and suspect on many digital meters.

I do have a vintage power supply with a variac feeding a TV power
transformer and its 6.3 winding is brought out to the front panel, so I
could get 1.2 as easily as I use that 6.3 and a fixed 6.3 in series to
get 12, except for the low voltages of filament windings.

Fact is, all our schemes work with pretty good safety for us and the
transformer. Your audio oscillator has less power than my filament
transformer so accidental lead shorts do no damage. At least they all
work handily for single phase transformers. Who has low voltage 3 phase
handy?

-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer