01-29-2014, 09:22 PM
The Bakelite block has 2 caps inside it. One end of each cap is attached to the ground lug at the screw end. One of the caps is attached inside to the middle terminal, and the other cap is attached to the terminal opposite the screw.
The original power cord was not polarized. If you want to connect it just as in the schematic, ignore polarity. One power lead goes to the middle lug of Bakelite, one power lead to the lug opposite the ground screw. One transformer primary lead to either of the Bakelite non-ground lugs, the other primary lead to the power switch. The other side of the power switch goes to the Bakelite lead that doesn't already have a primary lead on it.
If your replacement power cord is polarized, I'd do it a little differently. Connect the neutral power lead to either of the non-ground lugs on the Bakelite block. Connect the hot lead from the power cord to the power switch and then the other side of the power switch to the other of the non-ground leads on the block. Then put a transformer primary lead on each of the non-ground lugs on the Bakelite block. This gets your AC power off any components when your radio is "OFF."
I'm sure there is something grounded to the Bakelite ground lug, but I don't know what. Anything nearby that needs to be grounded could go there if there isn't another convenient ground point.
Are you replacing the rubber wires by desoldering them? If so, you might as well replace capacitors with modern ones at the same time (except the little mica caps that look like dominos) and resistors that are more than 10% out of tolerance. It's not much more work if you are desoldering anyway. Some restorers give resistors 20% and some replace them all, regardless.
It is most important to change the electrolytic capacitors with new 450 volt 'lytics before you even plug it in. They are no doubt dry and leaky. If they short, there goes your power transformer.
It's a good idea to replace the caps inside the Bakelite, too, because they will probably soon short or leak power to ground, and there goes your transformer. Replacing them is really easy, takes 15 minutes. You'd need to order modern Y or X/Y caps. And a lot of folks add a fuse to the hot side of the line, before the switch.
The original power cord was not polarized. If you want to connect it just as in the schematic, ignore polarity. One power lead goes to the middle lug of Bakelite, one power lead to the lug opposite the ground screw. One transformer primary lead to either of the Bakelite non-ground lugs, the other primary lead to the power switch. The other side of the power switch goes to the Bakelite lead that doesn't already have a primary lead on it.
If your replacement power cord is polarized, I'd do it a little differently. Connect the neutral power lead to either of the non-ground lugs on the Bakelite block. Connect the hot lead from the power cord to the power switch and then the other side of the power switch to the other of the non-ground leads on the block. Then put a transformer primary lead on each of the non-ground lugs on the Bakelite block. This gets your AC power off any components when your radio is "OFF."
I'm sure there is something grounded to the Bakelite ground lug, but I don't know what. Anything nearby that needs to be grounded could go there if there isn't another convenient ground point.
Are you replacing the rubber wires by desoldering them? If so, you might as well replace capacitors with modern ones at the same time (except the little mica caps that look like dominos) and resistors that are more than 10% out of tolerance. It's not much more work if you are desoldering anyway. Some restorers give resistors 20% and some replace them all, regardless.
It is most important to change the electrolytic capacitors with new 450 volt 'lytics before you even plug it in. They are no doubt dry and leaky. If they short, there goes your power transformer.
It's a good idea to replace the caps inside the Bakelite, too, because they will probably soon short or leak power to ground, and there goes your transformer. Replacing them is really easy, takes 15 minutes. You'd need to order modern Y or X/Y caps. And a lot of folks add a fuse to the hot side of the line, before the switch.
John Honeycutt
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