Working on a 2000A and attempting AM IF alignment (and later FM). The service manual shows IF passband curve shapes (pages 11 and 13) but there is no vertical axis reference such as dB or otherwise. From the diagram I could infer some relative percentage given where the curves inflect into the noise level, however in reality when sweeping an IF those inflections are buried in noise and no way to tell where the inflection or bottom line is. Even a simple statement like "5kHz wide at -6dB, 10kHz wide at -30dB" for AM would have been helpful. Is there a standard for HiFi receivers of the era that I am not aware of?
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IF passband shapes in service manuals
- Thread starter SteveFMT
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Watthour
Electron Rancher - JS3600
I went through a 3000A about 10 years, 2 months, and 2 days ago (2/15/16). After the initial repair it came back across the bench for a second go to get it fully functional. This thread might offer a little help:
I had all kinds of fun on the TRAM board after toying around with diode and tranny replacements. I abandoned the factory manual and instructions and did a conventional (typical) alignment using a generator and 'scope/meters, and simply peaking the IF stages (four of them on the TRAM-3). It took a bit of work to pull back into some compliance since I had changes some of the Germanium trannies in the front end (a fistful of 2SA102s) for silicon, with the necessary bias circuit changes. It worked out, but was nothing to get excited over in terms of performance. Still better than a dead AM section, and possibly as good as it ever was.
It's fitting, since this one was a complete pig when I opened it up (3000A). No doubt it entertained in a few parlors and places where the occupants were evidently heavy investors in foreign products, like Columbian, Haitian, Panamanian, and other varieties of their exports. A nice hot water bath with soap and a hot rinse got the all-brown components, parts, wires, and boards back to their original colors.
I thought it was a little odd that the matching transformers has...
I thought it was a little odd that the matching transformers has...
I had all kinds of fun on the TRAM board after toying around with diode and tranny replacements. I abandoned the factory manual and instructions and did a conventional (typical) alignment using a generator and 'scope/meters, and simply peaking the IF stages (four of them on the TRAM-3). It took a bit of work to pull back into some compliance since I had changes some of the Germanium trannies in the front end (a fistful of 2SA102s) for silicon, with the necessary bias circuit changes. It worked out, but was nothing to get excited over in terms of performance. Still better than a dead AM section, and possibly as good as it ever was.