The problem with aligning an FM tuner (including MPX), is that while the general process is the same for all units, the specific process is not.
In general, the IF "strip" is aligned first, followed by whatever discriminator design is used, followed by the RF "front end", followed by the MPX adapter.
But within that process, different manufacturers can have you inject different test signals in different manners at different places. Also, different designs can have you tune the various IF transformers to a peak that is only optimum for that particular transformer.
For virtually all modern Fisher gear (produced from say about 1958 or so), if the alignment is not too terribly out of whack, you can really perform a very good alignment on the tuner section proper (i.e. not including the MPX section) with nothing more than a good dvm.
In these units, Fisher had fully changed from the old "stagger tuned" type of IF strip design, where in each stage was tuned to a unique response such that together, all the stages in the IF strip produced the desired ultimate response in the end. It was these types of designs where the location of the particular tubes used in the IF strip was important, as casually changing them around could upset the alignment of the unit. In the newer designs, the transformers are merely peaked for maximum signal transfer, giving rise to the alignment method used in the later Fisher equipment -- not only when test equipment is used, but also in with the non-equipment alignment method outlined in the kit units. In these types of designs, specific tube placement is rather non-critical. In fact, in these types of designs, the adjustment that is most critical is that of the first IF transformer, since the actual frequency it is peaked at then determines the peak that the following transformers are peaked at. Therefore, if the first one is correct, then it will ensure that the following ones are correct also when they are peaked as the alignment process proceeds.
The one place you can get really screwed up is with the MPX unit. Tuning one by ear is risky business, as you may get it to work correctly -- but only on a couple of stations. Or it may work correctly, but only on very strong stations. Or work correctly, but the channels are reversed (who knew!).
Fortunately, Fisher built and aligned the MPX units separately from the ultimate tuner/receiver they were installed in, so for today's hobbiest, in a pinch, they can be removed, sent in for alignment, and then reinstalled. It is best of course by far to align the MPX unit in the tuner/receiver it is installed in. But a proper alignment on a unit removed from its tuner/receiver it is used with is almost always preferable to an adapter tuned by ear.
However, if only the separation control is out of whack (oops, I accidentally turned it), then a careful ear alignment of this control can work pretty well. But if the 38 kHz oscillator or 19 kHz pilot circuits are out of tune, then all bets are off.
Dave
