Piedmont, OK
One of the neat features on Gottlieb's Centigrade 37 is the backbox thermometer animation. The mechanism behind this is a little quirky and needs to be set up "just right" to work spot-on correct. The ribbon is advanced by a typical solenoid advance unit, and is reset by a spring just like you see in a credit unit. Unfortunately, this ribbon runs in a dirty environment and collects coil dust and other junk, and eventually will look pretty dirty. Replacing the ribbon with a new one makes a big difference:
WARNING! If you're thinking about cleaning your old dirty ribbon, do not wash with soap and water! Upon drying it will shrink up so much that you'll probably not even be able to reinstall it (ask me how I know)
Step-by-Step Removal and Replacement:
1) Start by taking out the three larger screws that attach the thermometer body to the wood board. They're on the bottom side of the thermometer:
2) Now take out the single screw holding the wire clamp in place. This is needed to allow enough wire length to remove the thermometer:
3) Open the board latch, and drop the board down until it rests on the stops
4) You will see another single screw right at the top of the thermometer, on the front side of the board. Remove that screw. Now the thermometer will be free to move.
5) Take out the 6 lights that light up the thermometer and set them aside.
6) Now, carefully remove the complete thermometer through the large square hole in the backbox light board. BE CAREFUL not to allow the thermometer to hit the back side of the backglass when removing it. There will be enough wire length to set the entire thermometer unit down along the bottom of the box, where you'll be working on it. Once you have the entire thermometer unit out, close and latch the light box board back up.
7) Remove the upper roller and shaft - the one at the top with the little springs attached - with a 5/16 socket and screwdriver. (see pic above)
8.) Remove the lower roller and shaft. This is the roller right at the bottom of the thermometer that the red side of the ribbon runs around. (see pic above)
9) Before you remove the aluminum wind-up wheel, I recommend marking how the wheel is "clocked" on the center mount boss. Using a sharpie pen, make a dot on the wheel, and another similar dot on the mount boss finger thats directly adjacent. These marks will be used later to eliminate guess work when putting the wind-up wheel back on.
10) Take the wheel off (three screws plus triangular plate) and remove it along with the attached ribbon.
11) Take the ribbon retention plate off by removing the small screw and make sure you catch the little nut inside when it comes loose.
12) Take the old ribbon off. If your C37's ribbon has factory glue along the plate, you can cut along the glue with a hobby knife and break it apart.
Congratulations - you're now ready to install the new ribbon and reassemble.
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First, a word of *CAUTION* about handling the new ribbon. If your hands are dirty, go now and wash. Dirty fingerprints on a brand new ribbon suck. They will definitely show up in the white portion. Also: don't allow the ribbon to get folded, kinked or otherwise abused when handling it. The kink/fold WILL be visible with lights on (ask me how I know). I ship new ribbons wound over a 3/4 PVC bobbin so they can't get messed up in transit, and this is the reason why. So from here on stay clean, work slowly and carefully and be nice to the new ribbon.
Reassembly instructions:
1) Start by mounting the new ribbon. Thread the red and white ends through the attach plate as shown in the pic below and install the little screw/nut but not tight at this point. Just tight enough so it doesn't fall apart. If the new ribbon has extra length (you bought one from me) thats fine - the extra length will be trimmed off later on. Here's how the new ribbon should look when mounted:
2) Put the wheel back in place on the mount boss. Use the two sharpie dots to get it correctly aligned with the mount boss. Leave these screws a little loose for now, so we can adjust the wheel position later.
3) Install the bottom and top rollers that you removed, making sure the ribbon is routed correctly (see picture). Make sure you don't over tighten the upper roller shaft nut, as the upper roller must be free to move in the slot. Reattach the two springs for the upper roller. Here's how the ribbon should be routed through the rollers:
Thermometer Ribbon Routing Thru Rollers
4) Its now time to adjust the red and white lengths on the ribbon. Manually increment the step-up solenoid until the thermometer is fully advanced (at the top mark).
5) Adjust the length of the red side of the thermometer ribbon so the red aligns with the top mark on the thermometer scale. Don't trim the excess ribbon quite yet.
6) Now adjust the length of the white side of the thermometer until the upper roller is centered in the slot. While adjusting the thermometer mechanism, its critical the ribbon tension is right. Too much tension on the springs will load the entire roller system up too much, and might inhibit the thermometer from resetting. So, take a close look at how the ribbon is tensioned here: the upper roller should be roughly centered and level in the slot. Also pay attention to see that the ribbon is aligned so its level and not crooked when viewed from the front side. Finally, when fiddling with the lengths on the ends, make sure the ribbon rides correctly on the wheel. It should be centered on the wheel.
7) Operational Test: Tighten down the ribbon retention plate screw, and manually increment and reset the thermometer to verify it works correctly: increment and reset. Watch for correct alignment, any skewing issues, and proper position on the wheel. We'll make final adjustments to the vertical position so the thermometer ribbon aligns with the marks on the front side in the next step.
8.) Fine-tune the thermometer position by adjusting the wheel position on the mount boss. There's some room on the wind-up wheel attach screw holes to allow for some movement here. Make sure you tighten these three screws after adjusting the wheel.
9) Using scissors, trim off extra red / white ribbon length by the attach plate. Here's how it should look:
10) Put the thermometer and lights back in place and HAVE FUN!
ADDITIONAL REFERENCE PICTURES
Perth
