[Hallicrafters] SX28 Restoration

[GARDGORE at aol.com]

1.    S-meter housing has split in many places. Are replacements available? 
Perhaps salvaged from a particular brand of meter? 

ANS: It is very common to find these meter cases split all around like flower 
petals 
> due to the stress put in the brass during stamping when it was made. There 
> are some good ones still out there but they scarce. You could pull 
> everything back in place with a couple turns of small diameter wire and 
> possibly solder the splits to repair it.
> 
> 2.    The main tuning shaft looks to have been knocked (bent). It appears 
> that the shaft with the main tuning knob rides inside an outer shaft (with 
> metal dial plate on it). Tuning is very rough and slipping. I will 
> completely disassemble the gear train anyway but is this shaft assy 
> serviceable? Is it a ball drive (gear reduction)? 

ANS: the reduction is by gear reduction with spring loaded split gears. If 
you 
> disassemble be sure you spread the gear halves to get some pre-load back on 
> them to prevent backlash. Have you had it apart enough to see that the 
> shaft is actually bent or could it be that the knob is damaged at its 
> mount?
> 
> 3.    The RF cover (top, sides and underside panels) are badly rusted in 
> places. The chassis itself looks to be OK under the thick layer of dirt! 
> These pieces will probably need to be sand blasted and replated. Anybody 
> done this? What kind of plating is it? 

ANS: Look under "metal finishers" or "metal plating" in the Yellow Pages to 
see if 
> there is anyone in your area. Please don't sand blast the parts though. This 
> could permanently damage the surface if your aim is to replate to restore 
> the surface finish to original. In addition sheetmetal parts could be 
> warped by the blasting media. Instead consider less aggressive glass bead 
> or acid (followed by neutralizing of course). Quality of finish is a lot 
> like painting, 90% of your results will be determined by surface 
> preparation. Swirl marks left behind by buffing with steel wool will show 
> up in the finished plating for example. The plating used on the SX-28 is 
> either cadmium or zinc depending on which parts. Zinc is brighter than cad 
> (when new) and easier to find platers for. Cad is starting to get hard to 
> find. Most cad plated chassis parts are what the platers call "clear cad." 
> I have had this done but I ended up having to send parts to an out of town 
> plater. Because of decreasing demand for cadmium plating and high 
> maintenance of the cad tanks our local plater converted his cad tank to 
> another zinc tank. I would recommend disassembling the chassis as much as 
> is practical, labeling parts, making notes and diagrams where everything 
> goes (don't try to rely on memory for this). Tie plastic bags around the 
> transformers and tape over holes on IF cans and other parts you don't want 
> water to get in. With cloth rags and an assortment of brushes carefully 
> clean everything with water and cleaner from plastic sprayer bottles and 
> dry out in the sun to then see what additional measures are needed to 
> restore its appearance. Plated parts can often be made to look good enough 
> again with a little careful cleaning and polishing with the various 
> available metal polishes. A little trick I use here came from a wise old 
> AWA collector a few years ago. It works so well I use it for all plated 
> parts now. Get some sodium bisulfate. This can be found as a pint or so of 
> granuals in a plastic bottle for $2 or $3. Look for pH down in the swimming 
> pool section of your local store. Mix about a teaspoon full in a cup of 
> warm water and immerse parts for about a minute. Remove parts and wash 
> right away if a stream of gas bubbles is observed indicating a reaction 
> which is rarely but occasionally encountered. Follow with a bath and 
> brushing of 409 and ammonia in a 50-50 mix. Plated parts will be bright and 
> shiny afterwards when the oxidation is removed.  This is especially 
> effective for cleaning and brightening old original hardware which adds a 
> nice touch to a job going back together.
> 
> 4.     All the knobs are original except the AVC knob, anybody have a 
> spare?
> 
> All of the aluminum parts are covered in a thick layer of white corrosion 
> that will need to be removed. The dials are in fair shape, not cracked but 
> do have a very light blotchy appearance that looks to be inside the 
> bakelite or whatever they are made from.

ANS: I received a tip recently from a chemical engineer to boil a teaspoon of 
"cream of tarter" in half a litre of water and use this solution to clean and 
brighten aluminum. I have not tried this one yet though. Be very careful with 
those dials! It is very likely the nomenclature will come off easily. Unless 
you are sure about what you are using to clean them beyond just brushing the 
dust off it is advisable to leave them alone. 

> 
> Most of the underside is original and will certainly require many new caps 
> and resistors. The Audio o/p transformer might be replacement - mounting

ANS: For excellent tips on recapping the SX-28 visit "Phil's Old Radios" page 
and click on the SX-28 link. A.B. Bonds might have posted something too. Do a 
search on "google" to find them.

73, Greg Gore; WA1KBQ


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