03-30-2016, 08:46 AM
I have finished the restoration of my Philco 37-670 cathedral and it works and sounds great. But the shadow meter is not working properly. It is the NEWER type with the round coil in back. I have read all of the excellent material found on the Philco Repair Bench, but no amount of pushing, pulling, or turning the coil will widen the shadow more than about 3/8". The coil resistance is about 1500 ohms. With no antenna connected, the voltage across the coil is 14.62. With a good signal that drops to about 5.9 volts and the shadow narrows to about 1/16" (same as if the rectifier tube is
pulled). So it appears that the receiver's AVC is doing its job.
When the shadow narrows only the RIGHT side of the shadow moves - the left side stays still. Is the possible that the coil is turned the wrong way - grossly mis-positioned (photo attached)? Right now, if the coil is pulled back all the way the leads exiting the coil limit rotation to within the gap on the back of the housing.
Is there a magnet inside that may have weakened and needs recharging? It's not obvious to me how to disassemble the unit and take a look. There is an excellent write up on servicing the earlier type meter on Philco Repair Bench, but I have not found anything on servicing the later type. Any suggestions?
