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Philco 19B Shadow meter
#1

Ive finally got this radio working after replacing the 1st IF transformer. Im looking at the shadow meter and Im not sure what I am seeing. This is my first attempt at one of these.
It looks to me that the vane stays centered all the time and doesnt move at all when tuning. It is very free to move when probed and it quickly returns to center when released (magnet ok).
http://www.philcoradio.com/tech/images/19v1.jpg
From what I understand, this is an early version and the circuit does not use a shunt resistor. If I understand correctly, with no shunt resistor in the circuit, the radio would not work if the shadow meter coil was open.
If that is true, Im thinking that the coil is ok.
So any ideas as to why isnt it working??
#2

Could be the magnet. Measure the coil just to make sure it is not open. Then read Chuck's page that has the article about the shadographs, and I think there is something about how to magnetize the magnet again.
Or maybe it was someone else who described the magnet procedure. Just do the search.
#3

Hunter your correct in that the schematic posted does not have the shunt resistor across the shadow meter. If the meter coil is open, you will lack plate voltage on two of the tubes in the front end of the radio. If the radio is working that coil must be good. Good movement is dependent on a strong signal in the front end of the radio.
Jerry

PS: Seems like someone tested meters out of circuit with perhaps a 1 1/2 volt battery to observe deflection. Perhaps someone can comment on that.

A friend in need is a pest!  Bill Slee ca 1970.
#4

Just put a prescribed current through whatever way. A higher voltage will require a resistor. I do not remember off the top what current it is and what the coil resistance is, but those are listed and then it is simple I=U/R thing.




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