The PHILCO Phorum
Shadow Meter Question - Printable Version

+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: Shadow Meter Question (/showthread.php?tid=21404)


Shadow Meter Question - jamr005 - 06-09-2020

I have a Philco Model 118 restored and playing great but I have no shadow meter vane action. I took the lens off and can see the vane. With the radio off the vane is facing the front (narrow side). I can move it with a toothpick and it appears to be spring loaded with the narrow side facing out as its rest position.  Is that right?
The part number is 2028 and it measures 1437 ohms so the coil is not open. The schematic indicates a 2900 ohm shunt but the as found one installed measures 1200 ohms. I have experimented with various shunt values (0 to 7K ohms) and there is no affect. No vane action ever.  Shouldn't the vane show its wide side (maximum shadow with the radio off, i.e. no station tuned in?  And what does it take to move the vane to the narrow position--more current or less current?
When I measure the voltage across the meter I get minimum voltage (and hence minimum current) on a strong station and a larger voltage (and hence larger current) when off station.  Does anyone know what the ma range is supposed to be, i.e. how much current to get the vane to move to cast a wide shadow vs. how much current to get the vane to face the front and cast a narrow shadow?
How do I fix this thing or do I need to look for a replacement? Maybe the vane is getting stuck on its pivot.  My next step will be disassemble it to see what is going on inside.
Here is the schematic:
http://www.nostalgiaair.org/pagesbymodel/125/M0013125.pdf

Thanks,
Joe

RE: Shadow Meter Question - Stall-U-Rated - 06-09-2020

When i tested the one on my 16b, i actually used a 9v battery to test the meter action (meter wires isolated from radio) Icon_smile

I noticed the meter action improved in the radio after i did the alignment procedure..

Steve

RE: Shadow Meter Question - Radioroslyn - 06-09-2020

Does the sm have a thumbscrew at the back of it?? If so it sets the tension on the vane. Too tight you have very little vane movement. Too loose the vane will bounce from side to side as you tune the set and will settle down after a few seconds.