04-27-2017, 07:38 AM
I checked the AM oscillator frequency again using a different method. The first time I counted the number of cycles in 10 divisions on the oscilloscope. This time I counted the number of divisions for one cycle. Here are the results of the 2nd test.
Bottom of band: 870kHz
Top of band: 1575kHz
This sounds low to me, but I would think it's close enough that I should get some stations...they'd just be offset on the dial, right? I'm thinking the 7F8 converter is bad since I don't get anything on any band. But one thing that makes me think that isn't true is that I was able to inject a 1000kHz signal into the antenna terminal and find it by tuning to it (see post 87). I've put the dial pointer back on and will try that again and see how close it is to the correct place on the dial, but that's just for info...it really doesn't change the diagnosis.
Any ideas from the experts? I can get a NOS 7F8 for about $10 so may just shotgun it and see what happens.
Rich
Bottom of band: 870kHz
Top of band: 1575kHz
This sounds low to me, but I would think it's close enough that I should get some stations...they'd just be offset on the dial, right? I'm thinking the 7F8 converter is bad since I don't get anything on any band. But one thing that makes me think that isn't true is that I was able to inject a 1000kHz signal into the antenna terminal and find it by tuning to it (see post 87). I've put the dial pointer back on and will try that again and see how close it is to the correct place on the dial, but that's just for info...it really doesn't change the diagnosis.
Any ideas from the experts? I can get a NOS 7F8 for about $10 so may just shotgun it and see what happens.
Rich
