[etech]

I picked up a Philco 70 with a bad field coil. I'm new to tube radios, and after some research, it looks like the field coil cannot be easily removed to be rewound (let me know if this is wrong). In order to move forward, I'll be hooking up a PM speaker (to use while finishing the chassis work), while looking for a good original (let me know if you've got one).

You are correct. The Philco 70 uses a field coil assembly which must be removed using an arbor press. The cone has to be removed before you can do this. While it is not impossible to do, you will not find many speaker rebuild shops willing to do this. When faced with this situation, I waited until one came up for auction on Ebay. The good news is that they are available pretty regularly on Ebay. The bad news is that they are somewhat pricey, typically going for $75 to $100 per copy. You will need the K3 type speaker which was used on the Philco 70 and 90 cathedrals. If you get one from a Philco 90, just be sure that it is for the middle version Philco 90 that uses the single 47 output tube. The other Philco 90 sets use a push/pull output arrangement and you would need to change the output transformer to use it. I hope this helps.

Best regards,

Ed