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Post by cablehack on Apr 24, 2018 8:21:43 GMT
According to the service manual, your machine has a one knob control (see p49 of the Scotch Yoke manual). Prior to 1938 they had two knobs. It mentions there's a sealing slug over the screw that holds the cover on, so sounds like the two knob version on earlier models. I've not dealt with single knob controls but the principles and method of construction looks similar. This is one of my CA controls www.flickr.com/photos/13469158@N05/8755451893/in/album-72157633054793795/and here you can see where the screw is hidden by the sealing plug. Just use something sharp and pointy to prise it out. The reason for the plug is that the screw is actually live at 120V. www.flickr.com/photos/13469158@N05/7984118741/in/album-72157633054818403/
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Post by mrhoot on Apr 24, 2018 13:01:04 GMT
Awesome so I had located the right spot already. The plug/cover in that hole is definitely not something that will pry out. It seems to be the same hardness as the body of the unit. I will try lightly drilling with a small drill bit unless advised against it.
Update: The slow drill worked perfectly. Popped the cap out gently and in one piece. I removed the cover and evaluated while looking at the scotch yoke manual. From what i can tell, the main contact that is intended to be actuated by spring armiture is not moving. I can move it with my finger, but twisting the control never moves it. I noticed that compared to the photo in the manual, the bellows look less inflated/filled which changes the position of that armiture that controls the contacts. If i pull the arm that the bellows push on towards the knob, adding tension to the spring for the contacts, then turn the knob, the contacts connect. Should i put the unit in the freezer/ put a heat gun on it to see if the bellows expand to put more pressure on the arm? .
I have been taking photos as I go. Will post when i figured out how.
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Post by birkie on Apr 25, 2018 0:22:24 GMT
I have been taking photos as I go. Will post when i figured out how. The easiest thing to do would be to upload to flickr, then click on the "share" icon, and select the "bbcode" tab. You can cut 'n paste the code, and that'll link to the images. For videos demonstrating how things move, upload to youtube and just paste the link to that
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Post by mrhoot on Apr 25, 2018 1:01:34 GMT
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Post by elec573 on Apr 25, 2018 2:47:35 GMT
Nice looking fridge. Did you download the scotch - yoke service manual from this site it has some pages devoted to what you’re working on.
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Post by mrhoot on Apr 25, 2018 3:00:43 GMT
Nice looking fridge. Did you download the scotch - yoke service manual from this site it has some pages devoted to what you’re working on. Yeah it has been pretty helpful. I understand what is goin on and not going on in my thermostat, just dont know if i can expand the bellows to put more tension on the bellow arm.
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Post by cablehack on Apr 25, 2018 9:32:47 GMT
The inside of the control looks good, but it does seem there might be a problem with the bellows. The normal pressure inside the bellows at room temperature is quite high - I had some difficulty reattaching mine, when I shouldn't have removed them (early days of my learning curve & no service manual back then). This is how much the bellows expand at room temperature www.flickr.com/photos/13469158@N05/7984118671/in/album-72157633054818403/Certainly at room temperature, the bellows should have more than enough pressure to force the contacts to close. At this point I'm suspecting a leak in the bellows or associated refrigerant tube. In that case, I'd suggest loosening the screws that hold the bellows to the back of the control. If the bellows don't expand as you do this, and you don't feel any pressure, that's what the problem is likely to be.
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Post by mrhoot on Apr 25, 2018 11:41:46 GMT
The inside of the control looks good, but it does seem there might be a problem with the bellows. The normal pressure inside the bellows at room temperature is quite high - I had some difficulty reattaching mine, when I shouldn't have removed them (early days of my learning curve & no service manual back then). This is how much the bellows expand at room temperature www.flickr.com/photos/13469158@N05/7984118671/in/album-72157633054818403/Certainly at room temperature, the bellows should have more than enough pressure to force the contacts to close. At this point I'm suspecting a leak in the bellows or associated refrigerant tube. In that case, I'd suggest loosening the screws that hold the bellows to the back of the control. If the bellows don't expand as you do this, and you don't feel any pressure, that's what the problem is likely to be. In the case that the bellows will not expand more, would that mean i need a whole new control?
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Post by mrhoot on Apr 25, 2018 12:58:50 GMT
It does not seem to be expanding at all.
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Post by birkie on Apr 25, 2018 13:01:53 GMT
In the case that the bellows will not expand more, would that mean i need a whole new control? Either that, or a new bellows from a donor control. If you're feeling adventurous, you could attempt to re-fill the bellows tube. I think those used methyl chloride. R152a (which is obtainable from certain air duster cans) is only 1-2% different. So you could try clipping off the end of the tube, evacuating it, and putting a little bit of R152a in so that there's some liquid (i.e the vapor us saturated), and see what happens. That is, unless there's a hole in it.
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Post by mrhoot on Apr 25, 2018 13:36:25 GMT
In the case that the bellows will not expand more, would that mean i need a whole new control? Either that, or a new bellows from a donor control. If you're feeling adventurous, you could attempt to re-fill the bellows tube. I think those used methyl chloride. R152a (which is obtainable from certain air duster cans) is only 1-2% different. So you could try clipping off the end of the tube, evacuating it, and putting a little bit of R152a in so that there's some liquid (i.e the vapor us saturated), and see what happens. That is, unless there's a hole in it. I have been thinking about both these options. The control is in such good shape other than the bellows issue that i feel like i should be able to pull off something creative. So I either need another flat top single knob with a dead condenser, or... The refill option. This machine is filled with SO2. I assume there is none in the bellows or tube. when i put a heat gun on it for a few seconds it would have expanded at least some i think. There is a threaded connection between the bellows cup and the temp sensing line. I cant find a hole anywhere. Im curious is there may be a problem at the back of the bellows where it connects to the cup. When you said ‘air duster’, do you mean the canned air that you can flip over and make a flamethrower/freeze burn things? If so, thats a neat idea.
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Post by birkie on Apr 25, 2018 15:44:51 GMT
When you said ‘air duster’, do you mean the canned air that you can flip over and make a flamethrower/freeze burn things? If so, thats a neat idea. Yup. Actually, you specifically want the kind that makes a flamethrower, because that's R152a (1,1-Difluoroethane) and it is flammable. I hope you can find/repair the leak, it'd be neat if this actually worked. While evacuating it would be ideal, you could probably get by if you squirted a excess liquid R152a into the tube, made sure it drained into the bellows, and let some gas and hiss out as it boils.. crimping the end shut once you think most of it had boiled off (but a little liquid remains). It'd probably displace most of the air and be OK enough. It might be a good idea to have it in the control when you filled it, that way you wouldn't have to clamp it. It could be satisfying to watch it expand and click the control 'on' before re-installing it and seeing if it'll actually cycle.
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Post by mrhoot on Apr 25, 2018 17:10:57 GMT
I hope you can find/repair the leak, it'd be neat if this actually worked. While evacuating it would be ideal, you could probably get by if you squirted a excess liquid R152a into the tube, made sure it drained into the bellows, and let some gas and hiss out as it boils.. crimping the end shut once you think most of it had boiled off (but a little liquid remains). It'd probably displace most of the air and be OK enough. Im thinking i can maybe take an ice pick/awl and open the original crimp just enough to get the canned air straw in, squirt some, then crimp the same crimp back closed. The other option would be to cut the temp sensing tube just above the crimp, fill, and recrimp. How easy would it be to overfill it?
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Post by mrhoot on Apr 26, 2018 0:15:26 GMT
Well good news and bad news guys.
The trick for refilling with the air duster seems to be completely and utterly VIABLE! I rigged up a piece of fuel line between the temp line and air duster straw with teflon tape. Turn the can over and pull the trigger and the bellows IMMEDIATELY fill and push the arm! The trick is timing the crimp immediately as/after the r152a passes.
Good news is that I think it works as a method and that i happen to have two pairs of pliers with the proper crimp slots to recreate the original crimp (thanks grandpa).
Bad news is that what I had suspected is true.
The fault is this: The bellows seem to have failed at their rear where they connect to to the cup and temp line. I was able to fill and crimp my line (i think, it all happens very fast) but my bellows immediately shrink as they cover with tiny frost. The cup surrounding the bellows shows a corrosion akin to that of a battery post on an automobile. I noticed this originally but hoped it was just a result of time when I know corrosion is rarely just time. I believe that corrosion is a result of the original SO2 blowing. I will add some photos of the process and the cup corrosion soon.
Guess i need to order a ramco to do for now, and start looking for a donor bellows and temp line.
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Post by elec573 on Apr 26, 2018 0:23:12 GMT
Don’t know your location but saw a rough looking fridge on craglist Pittsburgh pa you’re modal . Posts says 1$ but not sure if that’s starting price or something else. But worth a look see what you think. Maybe you can get some parts off it .
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