Any guesses? - Printable Version
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- Chuck Schwark - 11-20-2005
Is that an iron-core choke or a tapped inductor? Your schematic shows a tapped choke symbol.
DC cannot flow thu the circuit as drawn. The meter is essentially in limbo with only one INPUT termimal with a DC connection. Check the placement of that cap. It may be a bypass cap and not a coupling cap???
A Shadow Meter movement can only respond to D.C. current.
- Terry Judkins - 11-20-2005
It appears that the cap is there to block the DC from the output tube plate(s). The meter diode makes a DC pulsing current flow through the meter and back through the autotransformer. Looks like it would work to me....
- Chuck Schwark - 11-20-2005
Hmmm......yes, I see that now. A Shadow Meter is normally in series with the IF and RF tube's B+ line, straight DC current and pre-disposed my brain to think in terms of DC current.
I don't think it's acting like an auto-former though....
I see that as a tapped audio choke, tapping off part of the full AC component and the reduced audio currents then get rectified by the diode. The DC thus generated would be a steady DC, since this meter is supposed to be used with an RF gen with audio modulation on (steady tone on output tube). Think the way it's drawn threw me at first.
- Guest - 11-27-2005
Hello Phellow Philco Phans,
Here is an interior photo of the shadowmeter.
[Image: http://IzzyWeird.com/temp/philco-shadowmeter.jpg]
The thing behind the cap on the cover is a tie-point. The rectifier can be seen near the top right-hand side of the box, the thing with the screw head. It is also secured to a tie-point.
The center tap of the auto-transformer comes out as a wire from the opposite side and connects to the rectifier.
[Image: http://IzzyWeird.com/images/eyes1.jpg]
Izzy