[Steve D]

After restoring my model 60 chassis and powering it up there is no RF reception but the IF's tune up properly. I determined that the antenna coil has problems. It appears that this chassis was hit by lightening some time in the past and a patch job was done to repair it.  The wavetrap was gone and bypassed, with just a burn mark left on the chassis and the antenna coil ohms out shorted to ground on the secondary. 

I took the coil apart and determined that the secondary is good but the primary which is the small universal winding at the top of the coil was mis-wired.  The inside of the shield can and the inside of the coil form were charred which means that they were burnt out and replaced and the replacement was mis-wired, as one lead was connected to the start of the secondary. 

I removed the primary coil and it seems to read correctly but although the lead to the antenna is the finish and the start wire goes to ground, there is a tap on the coil that appears to be the junction of the 11 ohm coil and the 0.7 ohm coil.  The 0.7 ohm coil section appears to connect between the antenna and the tap, not the correct way it is shown in the schematic.

I have searched through the forum but still have not come up with a definitive answer as to how this coil should be connected.  From reading the search posts there might be another primary of 4? turns on the main coil form but I cannot find it on mine.  Wondering if the replacement primary was the correct one?  

Any help would be really appreciated. 

Thanks,

Steve D

[klondike98]

Here's some info in a thread on a 60MB I did. It has a link to further info from Ron and Chuck.

[Steve D]

Klondike98, thanks your fast reply.

After reading the links you posted I realized that the 0.7 ohm primary is wound at the bottom of the main coil and I couldn't see it as the overheating softened the wax and allow it to blob at the coil bottom obscuring the primary winding.  Once I scraped the wax away I found it and it is indeed open and oxidized.  The photo is after I removed it and you can see the color of the coil is darkened due to the heat. I'll rewind the primary and make a new bobbin for it as indicated in the attachments. 

The second photo is the AM band primary which although it has a tap winding, the main winding measures 11 ohms and should be usable if I cut off the tap winding lead.


       

Thanks again,

Steve D