[Hallicrafters] Aluminum panel warp?

[Barry Hauser]

Mike wrote:

> I've got an aluminum panel on one of my SX-42's and it exhibits a 
> pronounced outward bow.  Laid flat and face up, the middle of the 
> panel rises almost half an inch.  Frankly, I was amazed that Mike 
> Shelton was able to do such a great job of repainting it recently!  
> This bow, by the way, was in the panel when I bought the radio.
<snipped>
> Instinct tells me to remove the panel, span it across some wood 
> blocks positioned under the edges, and weight the center to "bend" 
> the bow out of the panel.  Experience, however, tells me that 
> instinct can be wrong.

Your instinct agrees with mine -- and some experience with panel
unbending.  However, if I'm not mistaken, the panels on the SX-42's are
steel, not aluminum, so might be a bit tougher.

One problem -- particularly if it's steel -- you have to bend or flex it
about twice the amount existing bend in the opposite direction to get it
straight when it flexes back.  Also, depending on the paint Mike used,
the panel may be more flexible than the finish and will crack or chip off
altogether. If there's any chance of this -- expecially after having the
panel professionally refinished, you may be better off finding some other
way to minimize the warp or compensate for it by shimming controls, etc. 
 (BTW -- why wasn't it straightened _before_ it was refinished?) 

If you decide to risk it, prop up the panel on two blocks with rounded
edges or some rags wrapped around them to avoid creating a crease. 
Position the blocks, 2 X 4's/whatever a bit outside the start of the bow.
 Put another (soft) rag over the panel and lean on it using body weight
and a sort of rocking motion -- pushing down, then releasing and
checking.  Don't try to do it all at once. Stop and check.  Your first
two or three attempt should be intentionally feeble -- just to get the
feel of it.  It may require so much force that you'll have to step on the
panel.  I have been known to use my knees for this, however, there are
penalties for "elbowing" ;-)  When it's close enough, do no more -- don't
try to make it perfect.  The panel screws should be able to take care of
the rest, especially if you've gone a bit too far, or a remaining warp
of, say 1/4 inch should be OK.

Again, the risk is that you'll crack the finish -- and some of the
silkscreening.  If you think so, think twice.  I have succeeded in
straightening out some panels and got away with it with little or no
cracking, but most of the time, it's at the pre-refinish stage.

Another way is to place one end of the panel on a carpeted floor, or
thick rag and hold the other end up at about 45 degrees.  Then, with your
"main" hand, press down on the middle, leaning into it a bit.  First, get
a feel for the flexibility, then "rock" it a bit and make your move. 
Going easy at first will give you an idea of whether you can fix it
without messing up the finish.  This technique has the advantage of
spreading out the force from edge to edge and provides some leverage and
control.  Actually, I think I'd try this before resorting to blocks, etc.


An alternative is to drill some additional holes and add screws to the
front panel.  However, this will make the rx "non-authentic" and simple
self-tapping screws may not be enough.  You may have to use nuts and
bolts, with the nuts and star washers epoxied or taped to the back of the
flange on the cabinet so you can start them in.  Or those clip on
retainers (speed nuts?).

Good luck.

Barry

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