Started restoring my recently acquired SX-28. It looks like a long road ahead.

Has anyone ever seen this before?

At first I thought the previous owner had used a slit saw on the meter case for some reason but then I realized they are fatigue cracks. Sometime in the past, someone had backed up the meter scale by gluing a piece of card stock as shown. Then perhaps used (maybe not the same owner) an excessive amount of illumination in order to see it. I managed to separate the two without damaging the meter face as shown. The meter's plastic face is distorted also.

Could heat build-up have caused these cracks?

My solution has been to install a 3" stainless steel radiator hose clamp, clamping it down just ahead of the meter movement mounting holes until the movement seats correctly. The meter movement works OK.




Thanks for any insight,

Bill

Don't know about Hallicrafters, but I've seen a lot of the same problems in the Hammarlunds from the late '40s. Strange, it doesn't show up so much in the WW2 Super Pros, but both the SP-400s and HQ129Xs all seem to have split meter cases. I assume it's a problem of heating by the light: the front is constrained by the bezel and the back expands. I've done some passable repairs by clamping the pieces back into shape, then soldering the inside and grinding it smooth.
Ed W2EMN

Very common across brands and I have used the same process described by Ed. At hamfests I have seen a bunch of fairly ugly repairs using hose clamps, cable ties, and a copious amount of hot glue in one particularly unfortunate case.

My solder repairs don't look perfect but they are passable. The good news is that the mounts I repaired several years ago didn't develop any new splits.

Rodger WQ9E

http://en.wikipedia.org/wiki/Intergranular_corrosion

The brass alloy used for the case was not a good choice for longevity. Same type of problem on some brass based 20's tubes and the later. metal ringed gtb octals, light bulbs.

I've also seen this cracking on works of art too.

I have a Hammarlund with the cracked meter case and and two Utah horn drivers with cracked cases.

Not a lot different from the problem with pot metal...

Chas

There was somebody offering a repair kit for the Hammarlund meters. It consisted of a thin wall brass tube that could just slide over the meter case o.d. and then be soldered in place. I haven't seen it offered for several years now.

I think you could make your own, starting with the closest undersize brass tubing available, and using a Harbor Freight muffler pipe stretcher to expand the ring to fit. It may take some heat treating of the brass between stretching sessions to anneal it and prevent it snapping.

--Chuck

I am not happy with the hose clamp either and the soldering technique sounds interesting. I will try it. I have to repaint the case anyway.
If that doesn't work I will try the brass ring solution. Maybe both
The original fix was duct tape with a #12 copper wire wrapped around and twisted together.
Thanks for the hints.

Bill

I have an SX 25 with the same problem. Looks identical to yours.

Lloyd Godsey, aka Skyrider, the gent who recently passed away made
a repair kit for the SX-28 meters a decade or so back. Unfortunately,
that is a very common problem for the SX-28 meter. It looks like some
one dropped a cherry bomb inside of the meter case Lloyd's fix
was a section of tubing that he had modified to slide over the meter
shell. I think he used something like the swedging tool used in
muffler repair shops on pipes.

Pete

I've restored these cases on occassion but have used my lathe and two torches one on either side....

By using two hose clamps to close up the breaks, then chucking the case and rotating it slowly, I'd heat it up enough and apply flux to the ID. I'd use the thinnest solder I had in the shop to insure that it melted quickly. Once the solder has coated the entire inside of the case, I'd wipe down the inside with a rag and let cool. When cold to the touch I'd remove the clamps. Repaint with a flat black. For some reason, the mounting holes won't line up exactly and I'd use the Dremel with a pointed abrasive tool to enlarge them a bit.


Seemed to work pretty well.

Just an update on this procedure.....

Instead of using hose clamps, which present a "flat spot" when you clamp down on the case, better results are attained if you use steel wire. Like a 20 ga. or 18 ga. wire. Reason being is that using wire and twisting it up will pull the leaves of the brass inward more evenly. Since the diameter of the case is fairly large, using hose clamps of that accomodating diameter won't work as easily as the wire and you'll see "steps" between the affected leaves of brass that will be hard to correct. Before, I'd use small shims to correct the problem however it gets difficult to maintain a perfect ID. This new procedure is much easier and quicker.

..try it, you may like it.

Two things I would do 1st anneal the brass, not going to need much heat cause it is so thin. Then make (turn) a wood or aluminum bar to the proper size as you squeeze the brass down the force will be spread more evenly. There is a lot of zinc mixed with the copper to make that brass, that is why it is deteriorating that way. tt

@1oldgoaly....

Never thought of a mandrel to align the leaves. It wouldn't be a bad idea. That's because I would solder on the inside of the case. When you apply soft heat to the case, wouldn't the idea of annealing the brass already come into play?

...Jim

Annealing brass is the opposite of annealing steel. For brass you heat it, then quench it in water to anneal it.

Jim,
Annealing 1st will allow the brass to be reformed to it shape easier, it will take the stress out of the brass, further cracking should be eliminated. Ed is correct on the annealing process, I haven't done a meter housing but old car lamps other old brass items. After applying the solder do you wipe it down with a clean cotton cloth, sorta like the way the old autobody men did when they tinned the spot they put lead filler back in the day? I can sling lead horizontal but vertical still is hard to do! tt

Ive used SS lashing wire (used by CATV line crews) for several years on those. Sometimes just leave it alone with the wire and other times silver solder the splits in spots as added "security". I never trusted just soldering as that just begs new cracks to appear.... being my luck.

Something else to try is to use the hose clamp to compress and hold and then form #10 or 12 bare copper wire all around and then solder in place . Maybe do it in two places.

The tubing is much more elegant, I'll have to look into that soon.

Carl

That's why a lathe comes in handy....

Using flux, of course, and the lathe turning maybeee 2 RPM, you don't need to wipe. If you can get the case to turn on it's axle using anything that'll do, it's a very quick job. Never used anything more than the newer style Bernz-O-Matic torch.

...Jim

If you want to clamp meter cases with wire, wire clamping has really caught on. Go here to see lots of stuff:

https://www.google.com/search?q=wire+cl ... 66&bih=785

I saw the double "T" shaped tool at an RV show years ago, and it is pricey, so I made one. On the URL above there is a picture of one that a guy made: http://www.google.com/imgres?hl=en&clie ... ,s:0,i:120

This tool really works.

Bill

OK, Could not find any thin wall tubing, brass or otherwise, in the local area. Settled for an ABS plastic plumbing coupling. Pics show the rest

From left to right: Plumbing coupling as purchased. Coupling with plug for support while chucking. Final sleeve.



Sleeve installed on meter.



Bill

Looks good!

Very nice!
And since you kept the original brass sleeve intact, they'll be no static interference from the PVC....if there was any anyway.