12-24-2013, 03:53 PM
hsusmann;
It is a considerable task to undertake. I would say only do it if you have some experience with IF transformers and the possibility of having to put new wires on them. Each radio will likely be different. Some are easier than others. I just discovered this morning that in this radio after I started the alignment, I was able to peak the IF signal in the first IF transformer and also in the 2nd. IF transformer plate circuit, but there is something not right in the secondary at the detector tube, so I am going to have to remove this one once again and check the parts inside. Right now I am thinking that either the cap across the secondary winding is bad (open) or one of the 100pFd caps at the low end of the secondary is bad (again maybe open). At least I know that the circuits from the mixer through to the 2nd IF transformer primary are working. If you are not afraid of dealing with the fine wires on the internal coils, then go ahead and give it a try.
Take good quality photos of the underside of the chassis before you begin and you may also want to make hand sketches of where every wire goes. I had real problems determining the color of the wires on this radio due to fading and the factory used some alternate colors other than what was shown on the schematic. There are always some confusion factors. I used cotton balls to cover the openings in the chassis above the trimmer capacitors in the front end. I could not get masking tape there using the best tools I had available. The only way would have been to drill out rivets, remove the trimmers and associated wiring. That would have been a far greater task than I wanted to consider. It is so easy to damage something in the front end circuitry.
There are lots of challenges in these old radios. Once it is up and running again it gives a great sense of satisfaction and accomplishment.
Joe
It is a considerable task to undertake. I would say only do it if you have some experience with IF transformers and the possibility of having to put new wires on them. Each radio will likely be different. Some are easier than others. I just discovered this morning that in this radio after I started the alignment, I was able to peak the IF signal in the first IF transformer and also in the 2nd. IF transformer plate circuit, but there is something not right in the secondary at the detector tube, so I am going to have to remove this one once again and check the parts inside. Right now I am thinking that either the cap across the secondary winding is bad (open) or one of the 100pFd caps at the low end of the secondary is bad (again maybe open). At least I know that the circuits from the mixer through to the 2nd IF transformer primary are working. If you are not afraid of dealing with the fine wires on the internal coils, then go ahead and give it a try.
Take good quality photos of the underside of the chassis before you begin and you may also want to make hand sketches of where every wire goes. I had real problems determining the color of the wires on this radio due to fading and the factory used some alternate colors other than what was shown on the schematic. There are always some confusion factors. I used cotton balls to cover the openings in the chassis above the trimmer capacitors in the front end. I could not get masking tape there using the best tools I had available. The only way would have been to drill out rivets, remove the trimmers and associated wiring. That would have been a far greater task than I wanted to consider. It is so easy to damage something in the front end circuitry.
There are lots of challenges in these old radios. Once it is up and running again it gives a great sense of satisfaction and accomplishment.
Joe
