Hammarlund SP-600 Dial & Gear Train Alignment


This section is provided thru the graciousness of Andy Moorer, and is used here with his permission. 


OK - here's the deal - throw out all the instructions. It is simpler than it seems.

    Manually rotate the shafts until you are at the lowest possible frequency. That will be when the vanes of the main tuning capacitor are fully enmeshed - that is, you can't get the moveable vanes any further into the static vanes. The little rotating brass piece that has the stop peg has to be up against the stop that is on the right-most brass gear. You have to fiddle with the gears until these things happen at the same time - capacitor fully closed and the rotating peg against the stop. If you are really adventurous, you can check it by winding all the way to the other extreme - the high-frequency stop should be when the capacitor is fully open.

    Note that it won't want to stay there. Here is where it takes 3 hands. Rotate it back to the low-frequency position, against the stop, capacitor fully closed. At this point, the fiducial (the little black pointer up top that bolts onto the faceplate on two hex spacers) and the frequency disc should be positioned so that it points right to a little mark on the disc to the left of the lowest frequency. Note that BOTH the disc and the fiducial (pointer) have some freedom and can be moved around some amount. Put the disc on with the screws loose - put the fiducial on with the screws loose. Holding the peg up against the stop, move each around to align them.

    Note that you might not be able to align them - that is, there may not be enough motion on the tuning disc. If this happens, you have to re-fiddle the gears. It means that the hub that the tuning disc bolts to needs to be rotated. You have to disengage it from the other gears and move it around a bit. Then go back to the beginning and get the stop, the capacitor, and the tuning disc and the fiducial all in the right place at the same time. After the third try or so, have a beer and come back tomorrow. It will go together the first time tomorrow. The vernier (the right-hand disc) lines up with its fiducial at zero at this same alignment position. The vernier dial doesn't have a special alignment mark - you just position it to zero when the tuning dial is at its alignment mark. Since that is the one with the stop on it, you generally don't have any problem with the hub being in the wrong position. Note that you have a fair amount of flexibility as to when the capacitor is fully "closed." That is, it doesn't have to be really, really closed. You are going to follow this whole thing with an alignment, which will adapt the rest of the receiver to whatever you end up with as the low-frequency position. It is more important to get the dial alignment mark to line up with the fiducial at the place the stop engages. That is, you don't want the operator to be able to tune lower than the alignment mark. If it does, you might not be able to get the high frequencies to align properly.

    Hope this helps. The instructions are often more confusing than helpful. If you get the disc, the stop, and the capacitor to all end up in the right place, then the radio can be aligned and everything will be wonderful. All other considerations are secondary.

James A. (Andy) Moorer


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