01-07-2014, 03:03 PM
Hi everyone, this is my first post here, but I've been lurking for quite a while. My name is Will, I'm 18 years old, and have recently gotten into restoring old radios. I started out with my grandfather's Zenith H723Z1 tabletop, recapped it and got it working really well. Then around Thanksgiving I found an 89 cathedral at a garage sale for $5 that I'm working on now. For Christmas I received a beautiful 40-190 skyscraper, and I also have a Trutone D-911 in bad condition. I'm completely hooked, and having a great time. This forum has been one of my primary resources, I hope you don't mind a few newbie questions 
I'd like to get a little help restoring the 89 here as I go along. So far I've tested the transformer (leaked a little wax and hums slightly, but all windings are good at the right voltages), the speaker coils, repaired the cone, recapped 3 out of the 8 bakelite caps, replaced the cord with a great looking rayon reproduction, and powered up the transformer with a dim-bulb tester.
Without the tubes, the pilot light came on and all the voltages were correct, and when the B+ line was disconnected, I measured about 400v DC off the 80 tube. So far everything is going well.
I have two questions right now. First, is there any way to test the speaker? I'm not sure what voltages to use, but with 100v on the field coil and a gentle audio source on the transformer you can hear the sound faintly. With the audio source directly on the speaker it's a bit louder but still quite faint. I know the impedances don't match up on either. If the speaker is broken I'll move on to another radio, I can't afford to replace it.
Second, while restuffing bakelite blocks I found a capacitor that isn't on the schematic. Looking at 89 Scematic, it is connected to the plate of the 75 tube and ground. It is a brown half inch square Micamold cap, with a single yellow dot on one side. It looks like it was likely soldered on later, perhaps to try to replace part 30 (also replaced with a paper tube cap), but soldered onto the wrong lugs of the block. Is there any reason to replace it, or should I just leave it out?
This 89 is the first revision code 123. My goal is to make it look as original as possible, so I'm restuffing everything and using cloth wire where possible.
Great forum, thanks for all the good information!
I'd like to get a little help restoring the 89 here as I go along. So far I've tested the transformer (leaked a little wax and hums slightly, but all windings are good at the right voltages), the speaker coils, repaired the cone, recapped 3 out of the 8 bakelite caps, replaced the cord with a great looking rayon reproduction, and powered up the transformer with a dim-bulb tester.
Without the tubes, the pilot light came on and all the voltages were correct, and when the B+ line was disconnected, I measured about 400v DC off the 80 tube. So far everything is going well.
I have two questions right now. First, is there any way to test the speaker? I'm not sure what voltages to use, but with 100v on the field coil and a gentle audio source on the transformer you can hear the sound faintly. With the audio source directly on the speaker it's a bit louder but still quite faint. I know the impedances don't match up on either. If the speaker is broken I'll move on to another radio, I can't afford to replace it.
Second, while restuffing bakelite blocks I found a capacitor that isn't on the schematic. Looking at 89 Scematic, it is connected to the plate of the 75 tube and ground. It is a brown half inch square Micamold cap, with a single yellow dot on one side. It looks like it was likely soldered on later, perhaps to try to replace part 30 (also replaced with a paper tube cap), but soldered onto the wrong lugs of the block. Is there any reason to replace it, or should I just leave it out?
This 89 is the first revision code 123. My goal is to make it look as original as possible, so I'm restuffing everything and using cloth wire where possible.
Great forum, thanks for all the good information!
