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Old 23-11-20, 23:01
David Dunlop David Dunlop is offline
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Join Date: Feb 2006
Location: Winnipeg, MB
Posts: 3,384
Default PLATES, Phenolic, Calibration ZA/CAN 4361

So! Let’s back up a moment to Post 435 and take a look at the area on the Sender front panel, directly above the PA LOADINGS decal between the two Counter Dials. Notice the empty pair of vertical holes? I did not, until last evening, and I was not impressed. Calm, but not impressed.

That is where the PLATES, Phenolic, Calibration goes. Mounted directly to the Sender front panel, and it is highly recommended this be done well before securing the front panel back onto the Sender chassis. The reason being, the two Dial Assemblies either side of the PLATES, Phenolic, Calibration, effectively block about 85 % of the access to the PLATES hardware location. There is no access at all from above or below. Silly me!

The bright side of all this was that after about 10 minutes of looking things over, I discovered it was possible to get my left hand in the Blower Door Access Hole, slide it in far enough to allow my left index and middle finger to carefully clear any contact with the left side Counters assembly and get the middle finger to reach both mounting holes for the PLATES, Phenolic, Calibration. The real trick, however, was going to be how to get each pair of lock washers and hex nuts over there to connect with their respective screws coming down through the Sender front panel, without all the bits getting scattered all over the place. I have had enough of that adventure for a while.

The first step of the solution I came up with was to take a couple of small drops of clear nail polish and glue the two lock washers to their respective hex nuts, being certain to keep the washers centred over the holes in the hex nuts and to keep any, and all, nail polish out of the threads in the nuts. Got that done successfully and they are now curing.

The second step, when I am ready to do the PLATES install, will be to glue the bottom of the hex nut to the tip of my middle finger with a drop of red nail polish and let it cure. Which will take about 15 minutes. The theory is the hardware set will stay put until the middle finger successfully avoids hitting anything and gets the hardware to the correct hole for the screw to be dropped into place and secured. Once the screw threads have engaged the hex nut to capture it, finger pressure will hold the nut in place until the lock washer starts to engage the back of the front panel, and I can let the hex nut twist free of my finger.

Having got all that sorted out, I then realized why I had not had the PLATES, Phenolic, Calibration all ready and waiting for reinstallation prior to remounting the Sender front panel to the chassis. This particular PLATES had a very bad bend in it. So bad, one could easily slide a new, closed manila file folder under the left edge of it and still have room to spare.

Earlier, I had thought I would simply replace the Sender PLATES with the one off my parts COILS, Aerial Tuning, only to discover it too had a curl to it, and the PLATES for the COILS were made by a different manufacturer than the ones used on the Sender. That had left me with the problem of whether or not it was possible to straighten out my curled PLATES to salvage it.

Some exploring on the Internet eventually revealed that people out there restoring vintage pinball machines from the 1930’s and 1940’s were faced with the same problem on their machines. Everything that lights up on these old games is hand painted artwork on plastic. A huge problem with these machines was the tendency of arcade owners to over lamp their machines to draw people to the newest games. The hotter bulbs took their toll on the plastic covers, frequently warping them.

The solution to this problem was to remove the warped plastic covers from the machines, lay them face down on a metal cookie sheet and place them in the oven at about 400 degrees F, leave the oven door open and sit and watch the plastic pieces until they slowly flatten out. This apparently takes about 10 to 15 minutes when the oven temp hits the 250-degree range. You then quickly remove the cookie sheet, put it on the counter and cover the plastic bits with something metal and heavy and let them cool for about 10 minutes. And they are flat.

I went a modified approach. I placed a sheet of parchment paper on the cookie sheet on the counter. Then put the PLATES, Phenolic, Calibration face down on the paper. Then I took a clear glass Pyrex baking dish with a smooth flat bottom and set it over the PLATES so I could watch it. Then I used a heat gun set on ‘High’, (about 500 F) and moved it back and forth over the dish while watching the PLATES. The weight of the dish flattens the PLATES for the most part, but I could still see the stress line at the worst part of the curve, so watched it. After 10 to 12 minutes, I could see the stress line disappear. I had oven mitts ready, so shut the heat gun off and carefully set it aside, relying on the retained heat of the baking dish to keep the PLATES flat. I had a small sheet of metal on standby with a small hydraulic jack. Removing the dish with my oven mitted left hand, I swung the metal sheet in behind it with my right hand and placed it on the plates, along with the jack. At this point, both the cookie sheet and the sheet metal and jack are acting as heat sinks. After 20 minutes, I removed the sheet metal and jack and removed the PLATES for inspection. Nice and flat with no damage.

The attached pictures show the before and after heating set up, and the edge on views are the Sender PLATES first, with the COILS PLATES next. You can see the amount of light getting under each. The Sender PLATES was originally twice as curled at the COILS one is in the photo.

I shall see if I am up to reinstalling the PLATES on the Sender tomorrow.

David
Attached Thumbnails
PLATES, Phenolic, Calibration 6.JPG   PLATES, Phenolic, Calibration 2.JPG   PLATES, Phenolic, Calibration 3.JPG   PLATES, Phenolic, Calibration 4.JPG   PLATES, Phenolic, Calibration 5.JPG  


Last edited by David Dunlop; 24-11-20 at 02:45.
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