06-12-2025, 09:34 PM
Ok, I think I'm about done. I've got one anomaly left but other than that, it is working great and picking up lots of stations, including on bands 2 & 3.
Here's the "anomaly"...
I kept getting stuck at the tuning stage where I was to tweak the two ganged trimmer capacitors, 36A for the RF stage and 36B for the Det-Osc stage. 36A seemed to have a little effect but 36B had none. Both of them would occasionally spike to a much higher voltage but that was all, just a spike. I took them off to clean them. While they were off, I turned the radio back on and when I did, the signal amplitude jumped up to about what I was expecting to see. It could receive lots of stations and they were all strong and clear.
That's when I took a closer look at the trimmer setup and realized that whenever they were installed, they were shorting the signal. As you can see in the attached pictures, there is a thin plastic insulator that goes over the mounting post -- the mounting post is chassis ground -- then the trimmer goes over the post and is held in place with an insulator and cap nut. Then a screw goes through the spring-tensioned end of the trimmer to adjust the trimmer up and down. The problem is that unless you have carefully held everything in place such that the trimmer mounting hole, which is bigger than the mounting post, does not touch the post when you tighten the cap nut down onto the top insulator, then the moment you insert the adjusting screw you have a signal short to ground. I got lucky once with 36A.
So, as far as this old beast is concerned, I can just leave these trimmers out and everything will appear to be working perfectly -- which I may end up doing. But my curiosity makes me want to at least understand if this is the normal mounting components for these trimmers or if, like most everything else, has been jury-rigged over the 88 years it's been in operation. Is there a different setup, or perhaps a little bushing for the trimmer than what I have? Perhaps these insulators once had a ring/shoulder on one end that kept the trimmer centered?
Thanks for all the help I've received from you fellas, and it looks like I've managed to stumble through putting it to good use. Just once more if you would...
Here's the "anomaly"...
I kept getting stuck at the tuning stage where I was to tweak the two ganged trimmer capacitors, 36A for the RF stage and 36B for the Det-Osc stage. 36A seemed to have a little effect but 36B had none. Both of them would occasionally spike to a much higher voltage but that was all, just a spike. I took them off to clean them. While they were off, I turned the radio back on and when I did, the signal amplitude jumped up to about what I was expecting to see. It could receive lots of stations and they were all strong and clear.
That's when I took a closer look at the trimmer setup and realized that whenever they were installed, they were shorting the signal. As you can see in the attached pictures, there is a thin plastic insulator that goes over the mounting post -- the mounting post is chassis ground -- then the trimmer goes over the post and is held in place with an insulator and cap nut. Then a screw goes through the spring-tensioned end of the trimmer to adjust the trimmer up and down. The problem is that unless you have carefully held everything in place such that the trimmer mounting hole, which is bigger than the mounting post, does not touch the post when you tighten the cap nut down onto the top insulator, then the moment you insert the adjusting screw you have a signal short to ground. I got lucky once with 36A.
So, as far as this old beast is concerned, I can just leave these trimmers out and everything will appear to be working perfectly -- which I may end up doing. But my curiosity makes me want to at least understand if this is the normal mounting components for these trimmers or if, like most everything else, has been jury-rigged over the 88 years it's been in operation. Is there a different setup, or perhaps a little bushing for the trimmer than what I have? Perhaps these insulators once had a ring/shoulder on one end that kept the trimmer centered?
Thanks for all the help I've received from you fellas, and it looks like I've managed to stumble through putting it to good use. Just once more if you would...