09-17-2015, 09:50 PM
Before you put the oscillator coil back in the radio, you might do two things:
1) Bake the coil in the oven at about 200 degrees F. for an hour or so. (No higher temp, a little lower will be fine.) This will melt off the wax that could be trapping moisture and drive off any moisture that could have been absorbed by the coil form.
I got this advice from Ron Ramirez, who said the wax that was added as a moisture barrier actually traps moisture, so it is just as well to melt it off.
2) Measure the resistance at each terminal, and if any is high, reflow the solder at each connection. You can inspect the connection to make sure the tiny wires are actually being wetted by the solder.
I had a 40-150 (probably with the same coil you have) that would not receive short wave at all. Several of the terminals read around 50 to 60 ohms when they should have read less than 5 ohms (if I remember right.) You might need to use some fresh rosin-core solder rather than just reflowing the existing solder. In my case, it took 2 or 3 tries to get the resistance down below 10, but since reflowing made any difference at all, it meant that the solder connection resistance was a problem.
After baking and reflowing the radio picked up SW really well.
Oops, I see you said you'd removed it from the circuit. I thought you meant you'd removed the coil from the radio. It's still worth a try, and it isn't that hard to pull the coil and put it back in. Make careful drawings and notes about which wire goes where!
1) Bake the coil in the oven at about 200 degrees F. for an hour or so. (No higher temp, a little lower will be fine.) This will melt off the wax that could be trapping moisture and drive off any moisture that could have been absorbed by the coil form.
I got this advice from Ron Ramirez, who said the wax that was added as a moisture barrier actually traps moisture, so it is just as well to melt it off.
2) Measure the resistance at each terminal, and if any is high, reflow the solder at each connection. You can inspect the connection to make sure the tiny wires are actually being wetted by the solder.
I had a 40-150 (probably with the same coil you have) that would not receive short wave at all. Several of the terminals read around 50 to 60 ohms when they should have read less than 5 ohms (if I remember right.) You might need to use some fresh rosin-core solder rather than just reflowing the existing solder. In my case, it took 2 or 3 tries to get the resistance down below 10, but since reflowing made any difference at all, it meant that the solder connection resistance was a problem.
After baking and reflowing the radio picked up SW really well.
Oops, I see you said you'd removed it from the circuit. I thought you meant you'd removed the coil from the radio. It's still worth a try, and it isn't that hard to pull the coil and put it back in. Make careful drawings and notes about which wire goes where!
John Honeycutt
