[RodB]

They are not directly interchangeable, but you could get it to work providing it physically fits. The shadow meter from this group of Philcos were pretty much physically the same. The main difference is the circuitry. The coil for the 645 is listed as 500 ohms and the 630 is not listed but has a 4K resistor in parallel. From experience I believe it's around 2K. Doing the math you can use a 680 ohm resistor in parallel with the coil of the Philco 630 shadow meter to get the 500 ohms and wire it in place of the broken one. Plus, you get the additional benefit of not loosing the radio signal if the coil should open in the future.