[Hallicrafters] SX-28a questions

[Joe Connor]

Jon:

     Here are some suggestions:

     1. Here are several articles on these sets that you might find helpful:

        http://antiqueradio.org/halli12.htm
        http://www.radioblvd.com/SX28Notes.html
        http://www.tuberadio.com/sx28/sx28.html

     Also, download the military manual from BAMA. It is far more extensive than the civilian manual.

     2. Don't apply power again until you've replaced the canned filter caps andthe audio caps. The audio caps are almost always leaky (C-42, C-45, C-46). Trace out the wiring from the canned caps. If I remember correctly, some caps with different voltage ratings are contained in the same cans. Realistically, these caps should be replaced before any power-up is attempted. 

     3. Wasn't Archer at one time the trade name for Radio Shack components? It seems a bit odd that a skilled repairman would use an Archer universal audio xformer and run the leads through a hole in the chassis. That sounds more like a tinkerer. Therefore, you might want to pay special attention to whether the xformer is an appropriate replacement for a push-pull audio circuit and whether it is hooked up properly. The successor-in-interest to Peter Dahl makes exact replacements for the the SX-28 audio xformer, although they are quite pricey. Hammond makes universal replacements that will work well at a more reasonable cost. If you use a universal replacement, it will have an 8-ohm output. The original xformer had both 500 ohm and 5k ohm outputs. I recently used Hammond replacements in a NC 2-40D and S-27 and was quite satisfied with the results. 

    4. I understand your concern for the power xformer (T7). Hopefully, the blown fuse was caused by bad caps instead of a bad power xformer. Hopefully, the fuse saved the xformer from permanent damage. Do you see any sign of a xformer meltdown, such as wax leaking out under the chassis? That's why it's a good idea to replace the canned filter caps before powering up.

    5. As long as you have a variac, don't run this set at more than 110 VAC. Once you have the set working, you might want to rig up a bucking xformer to knock the input voltage down to 110 or so.

    6. The bandspread dial cord is only a moderate PITA to replace.

    7. I can't help with the coax on the selectivity switch. There were a lot of articles published over the years on modifying and "improving" these sets.

    8. For the antenna and ground terminals, you could probably use modern binding posts until you can locate originals.

    Keep us posted. THese are great receivers and well worth the time and effort to restore.

                                                  Joe Connor


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