[Today’s run: 3.4 ]
Like a lot of my projects, about 80% is working up the motivation and the idea about how to do the thing. That’s the problem with being a perpetual amateur: I don’t do these things often enough to get a professional type frame of mind and angle of attack.
I did read the troubleshooting information in the manual I downloaded. That helped.They outline a general back-to-front attack: start with the audio output and work back toward the front end where the antenna connection is. I injected an audio signal and that came out. Then I was a bit confused as to whether the audio driver was working correctly or not. I sat on it for awhile.
Yesterday I decided to check the various oscillators to see if they were working. The manual talks about using a receiver to listen for them, so I did that. The front end crystal oscillators and the VFO appeared to be working. I had a length of coax and I attached a little coiled wire with some clip leads and I moved the coiled wire around. I used my SDRplay and I could see everything on the spectrum/waterfall display.
I got to a stage where there is a 405 kHz oscillator which mixes down 455 kHz to 50 kHz. And I could not find the 405 kHz signal. There is an oscillator in the grid/cathode circuit which had 2 resistors, 2 capacitors and a canned coil. I put my little loop over the top of the oscillator tube and.. nothing. I tried to measure the component values and everything seemed to measure OK. But I still couldn’t get any sign of the 405 kHz signal. Swapped tubes, tried everything.
So I ended up taking that canned coil and the attached components out. I detached the components and measured them. I measured the coil. Everything looked good. I put it all back together and put it back in. And the 405 kHz oscillator is back larger than life. I had to adjust the coil a bit, easy as can be. Now the radio is playing like it never had a problem. Maybe it was a cold solder joint or something, I don’t know.
I’m going to let it play this afternoon then maybe I will run through the “tune up” procedure this evening and peak all of the IF cans and such.