11-12-2015, 04:52 PM
Now that I have the Loctal socket replaced, I can look into getting this radio to work.
[Image: https://lh3.googleusercontent.com/-UPV5r...520018.jpg]
When I received the set it had a toggle switch in the back labeled “radio/phono,” and the switch wiring had been removed or cut. After restoring all the wiring and components I checked the continuity using a Sams resistance table. That showed a problem with B+ return to B-. Each B+ point should have given either 90Kohm or 560Kohm. Instead, I got multiple Megohm readings which varied, always increasing while I tested, from 2 to 30 Meg.
I went ahead with the variac and gradually increased the voltage to 120V and the pilot light and tubes all lit up. When I powered up again, I apparently killed the 50A5--first in the string of heaters.
Weeks have passed, and I’ve gone over the circuits dozens of times and found no problems. That is, it looks just like the schematic to me. But when I look at the schematics, I can’t see how B+ is supposed to return to B- or the chassis without jumping over a capacitor.
I replaced the 50A5 and went on with voltage testing at 60VAC input. The voltages all look pretty good. If the values are doubled, they approximate what it says in Sams and Rider. During voltage testing at max volume/no signal the radio starts playing when I touch certain B+ points (Is the meter providing a path to B-?).
So, I think the whole problem is that I’m missing some connection from B+ to B-. This is a link to a very legible scan of the Rider schematic:
https://goo.gl/photos/z4KG89Ze1LSp6PaY9
It’s been marked up to show modifications I’ve made (red) and voltage readings (red). Also, there’s one cap that wasn’t in the schematics (green).
Please excuse the long explanation above. I had to express how much effort I put into this before asking for help. The question is:
How does B+ return to B-?
Thanks. I appreciate any advice.
[Image: https://lh3.googleusercontent.com/-UPV5r...520018.jpg]
When I received the set it had a toggle switch in the back labeled “radio/phono,” and the switch wiring had been removed or cut. After restoring all the wiring and components I checked the continuity using a Sams resistance table. That showed a problem with B+ return to B-. Each B+ point should have given either 90Kohm or 560Kohm. Instead, I got multiple Megohm readings which varied, always increasing while I tested, from 2 to 30 Meg.
I went ahead with the variac and gradually increased the voltage to 120V and the pilot light and tubes all lit up. When I powered up again, I apparently killed the 50A5--first in the string of heaters.
Weeks have passed, and I’ve gone over the circuits dozens of times and found no problems. That is, it looks just like the schematic to me. But when I look at the schematics, I can’t see how B+ is supposed to return to B- or the chassis without jumping over a capacitor.
I replaced the 50A5 and went on with voltage testing at 60VAC input. The voltages all look pretty good. If the values are doubled, they approximate what it says in Sams and Rider. During voltage testing at max volume/no signal the radio starts playing when I touch certain B+ points (Is the meter providing a path to B-?).
So, I think the whole problem is that I’m missing some connection from B+ to B-. This is a link to a very legible scan of the Rider schematic:
https://goo.gl/photos/z4KG89Ze1LSp6PaY9
It’s been marked up to show modifications I’ve made (red) and voltage readings (red). Also, there’s one cap that wasn’t in the schematics (green).
Please excuse the long explanation above. I had to express how much effort I put into this before asking for help. The question is:
How does B+ return to B-?
Thanks. I appreciate any advice.
