Audio Systems: Poor dial tracking on vintage shortwave radio, rf signal generator, canadian marconi

Question
Hello;  Not sure if you'd be interested with problems in an antique console radio I am restoring,that said, perhaps you could pass this request on to another person.   The radio is a Marconi all band set (5 Shortwave plus Standard Bdc'st).  The chassis has been recapped & thoroughly checked over. The set sounds very nice and is very sensitive on all bands since I completed an alignment, the only nagging problem is three of the shortwave bands do not track stations accurately from appr. 1/2 way along to the top of the radio dial.  I referred to the factory service sheets for this set for alignment procedures, am using a new R.F. generator(zero beat each freq. against a Grundig digital all band portable for optimum accuracy).  The bands are all very sensitive to weak stations but; I.E.;  Shortwave band( 6mhz. to 16mhz.), 6mhz. shows as 6mhz. on the dial but 10mhz.shows as 9.1mhz. on dial and 16mhz. shows as 14.1mhz. on the dial.The freqs. seem to compress as you go up the dial. I have gone over the alignment many times now but cannot seem to improve this one fault.  I have hopes you people can suggest a cure.   BTW;  The Model No. is 206 - 207 Canadian Marconi(1940ish).  Many thanks !  Regards, Don Eaglesham-- --missye@telus.net   Calgary,  AB.,  Can.

Answer
Dear Don,

My guy didn't know, but asked a friend of his who's into this sort of thing. This is his response.

"It depends on the construction on the radio. With most, you align the IF's to the proper IF frequency. Make the high end track by setting the dial on the highest frequency in the range. Set the RF signal generator to the same frequency. It should be modulated at 400cps at 30%. Adjust the trimmer capacitor on the oscillator tuning capacitor to match that frequency. The high end is now tracking.  Peak the trimmer on the tuning gang for that band as described by the alignment instructions. Then adjust the oscillator coil as follows. Pick a frequency at the low end of the range for the band. Set the RF generator and the radio to that frequency. Observe the output on a sensitive meter or better a scope. Adjust the dial to a very slightly higher frequency, and adjust the oscillator core for a peak then go slightly lower and do it again. The idea is to rock the generator and oscillator coil until you find the greatest peak. If all parts are at original factory specs, the radio will track. If it doesn't, that can be fixed depending on the circuit. Some radios have oscillator padders that can be adjusted to make the low end track. If there is no padder, you can add one. In many radios, tracking is accomplished by very slightly bending the plates on the tuning capacitor. Some tuning caps have slits in them to make this easier. Do this VERY gently, a tiny bit affects tracking, and the plates can only be flexed so many times.
It's also important not to bend the plates far enough to create a short circuit.

That's it. If you are still having an issue, send me the model number, I'll look up the schematic, and try to give more specific advice."

Of course, if you need him to consult the schematic, let me know thru allexperts, and I'll pass it along. I'd refer you directly, but I don't have his email address or permission. Will work on that.

Kindest regards,

Kevin