01-31-2019, 11:18 PM
I finally made a little progress toward solving my FM problem, but still no FM. With some troubleshooting help from Radioroslyn (thanks Terry!) I decided I probably had a bad 2nd IF can so I posted ads here and over at antiqueradios.com looking for a replacement. I found a very generous forum member over there that sent me all 3 cans from his spare 47-1230 chassis. And I'm glad he did. The replacement 2nd IF made no difference. So I removed the 3rd IF and tacked in the replacement and then tried the FM alignment. In the procedure they have you monitor the voltage across an electrolytic cap on one of the diodes in the 7X7 detector and keep it at around -10v. Previously I was never able to get much over -6v, but with this replacement IF can I have to constantly adjust the output of my generator to keep it at about -10v. So, a major step forward! And it's one busy little transformer:
But, still no FM. I'm pretty certain the oscillator is not running. In the test procedure there is a test to determine if it's running and it fails. So I'm looking for ideas. Maybe someone has their 47-1230 on the bench and can show me a picture of their FM oscillator coil so I can compare to mine to see if it's spread similarly. I hate to start compressing or expanding the coil to see if I can make it resonate but that might be what I have to do. Here is what mine looks like:
Thanks for any help or suggestions!
Rich
But, still no FM. I'm pretty certain the oscillator is not running. In the test procedure there is a test to determine if it's running and it fails. So I'm looking for ideas. Maybe someone has their 47-1230 on the bench and can show me a picture of their FM oscillator coil so I can compare to mine to see if it's spread similarly. I hate to start compressing or expanding the coil to see if I can make it resonate but that might be what I have to do. Here is what mine looks like:
Thanks for any help or suggestions!
Rich