>
>As a follow-up to my earlier post:
>
>I measure the L7 filament voltage at 5.14 VAC using the aforementioned
>Fluke 77 DVM.
>
>An oscilloscope across this same test point shows no power-on 'bang' - so
>the transformer is performing well in this manner, no inrush surge to worry
>about.
>
>So guys, should I bother with fiddling about 0.14 volt? This is 2.7% high,
>per my calculator...
>
>
Steve: 3% high cuts the emissive life in half. 6% high cuts the
emissive life by 3/4. {see amplifier article in Jan. 1994 QST for
details} // To measure the inrush current you need to measure the peak
voltage drop across a known series resistance with the oscilloscope. The
fil choke can serve as the known series res. To measure the resistance
of the choke, pass 1.00 ampere DC through the fil. choke and measure the
potential dropped across the choke with a DMM. A typ. value might be
5.0mV - which means that the choke has 5.0 milliohms. // Connect the
oscilloscope across the 5.0 milliohms. Start the amp. and measure the
peak v. Current equals volts div. by 0.005 ohms.
>
- later
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|