[Today’s run: two miles with the dog ]
We got all of the wax/paper capacitors replaced and all of the electrolytics. It fires up and I get signals.
I have been working through the alignment procedure as given in this manual.
My picture for today is the schematic diagram. The antenna hooks up at the left.
The first thing in the signal path is a switchable selection of tuned circuits, one for each of the five “bands” which altogether cover 0.55 mHz to 37 mHz (or something like that). You can see that there are three sets of these tuned circuits. They work in concert with the big dial on the front, behind which is a triple-section air-variable capacitor (“bread slicer”).
Switching the band switch will put into operation the three tuned circuits for that particular band. Turning the big knob on the front then changes all three tuning elements at the same time giving you selective tuning within that band. Hopefully everything goes in coordination.
The first thing is a tuned circuit for this band, tuned at the RF frequency we want to listen to. Then there is a 6K7 tube which amplifies the remaining signal. After that we have the “Detector” tuned circuit which works just like the RF circuit. The output of that is fed into the 6L7 tube. At the same time the Oscillator tube 6C5 is creating a coordinated signal which also is fed into the 6L7 (mixer). The output of the mixer is our Intermediate Frequency, somewhere around .455 mHz. Then there are some more tubes to amplify and mix it down to audio, and two big 6L6 tubes to move the speaker.
I’ve run into a problem with the first tuned circuit (RF). There are adjustment capacitors which I am supposed to use to “peak” the output of each circuit for each band, so that the desired signals are strong into the 6k7 tube. But I’m seeing the actual peak is outside of the range of the adjustment capacitors, for all bands. So I do hear signals but I’m not aiming straight-on to the signals that I want to hear. Kind of like having central vision loss and having to look sideways in order to drive… not the best by far.
I have put out the word on an internet site where old-radio guys hang out: I’m looking for some ideas on what the problem might be and how to fix it.
