Refurbishing Century Edkotron

microstar

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Jan 19, 2014
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Lawton, OK
I just acquired a Century Lighting Edkotron #281 Control Unit on eBay. Why, you ask. Well, I worked with one in grad school 50 years ago. It is also a historically significant milestone in lighting history; check out Derek's Wiki page for details. The #281 Control Unit is a simple controller with 6-channels and a master supplying a 15 volt half-wave DC signal to the dimmer pack via standard 10-pin CJ connectors. As the photos show, my unit is complete (except that the original on/off key switch has been replaced by a toggle switch) but the paint has completely deteriorated.
As received only the master pot and channels 1-3 are functional, so I plan to completely disassemble and refurbish as much as possible. Oddly enough, I have an original instruction manual for the Edkotron system, which is quite helpful.

281 Frnt Panel.JPG 281 Circuit Bd.JPG 281 Pots Switches.JPG
 

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Mac Hosehead

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It sure looks as if a diode was replaced at some point. If a potentiometer is bad I would think there is some chance in finding a replacement but if the nylon gear that slides over the shaft is bad then I'm not sure where a good one could be found.
 

DrewE

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Vermont
If a potentiometer is bad I would think there is some chance in finding a replacement but if the nylon gear that slides over the shaft is bad then I'm not sure where a good one could be found.
It may very well be hard to find the gear commercially, but it looks like the sort of part that could be 3D printed with only a little bit of effort. A resin printer could do it quite easily; an FDM printer probably would need to be in fairly good tune and might need some trial and error to get well-shaped gear teeth of that size, but it should still be quite possible. (It would even be possible to print in nylon, with the right setup, but other plastics that are less finicky to print would also be entirely serviceable in this application.)
 

ship

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I believe I have one working and intact in the museum. Contact me off line in sending it to you for take apart/testing or sending it to where I work to restore your's - experts on staff.
 

JonCarter

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Apr 18, 2011
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Meridian, Idaho, US
If you need gear(s) . . . Some years ago I needed some small nylon gears to repair an H-P printer. I found a source for such items but can't think of it offhand. Give me a couple days . . . .
 

microstar

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Jan 19, 2014
Location
Lawton, OK
I have begun disassembly to see what parts need fixing. Fader pots are CTS brand 4K linear taper, so will be researching replacements. The splined shafts on a few pots I have laying around
are too small in diameter to fit the small gear. Interesting that the inner diameter of the small gear does not have teeth to match the splined pot shaft; it just relies on a friction fit. The first pot
I tested has a bad spot resistance-wise near the center of rotation. It is pretty well sealed against spraying anything like Deoxit Fader Lube inside. Wondering how hard it would be to bend up
the four tabs that hold the thing together and open it up. Will try it on a junk box pot first and see how it goes. Some photos of the fader assembly. This is the most heavily damaged inside gear track:

281 gears1.JPG 281 Gears2.JPG 281 Gears3.JPG 281 Gears4.JPG 281 Pot1.JPG 281 Pot2.JPG
 

FMEng

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You should be able to find the same sort of pot, but I doubt you will find any with a stubby shaft like that. That may have been a custom product for Century. Replacements will have longer shafts, and you might have to settle for nylon instead of metal. Just cut the shaft to length.
 

microstar

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Jan 19, 2014
Location
Lawton, OK
You should be able to find the same sort of pot, but I doubt you will find any with a stubby shaft like that. That may have been a custom product for Century. Replacements will have longer shafts, and you might have to settle for nylon instead of metal. Just cut the shaft to length.
The original shaft measures 6mm diameter and like you have said, I think I've found a replacement with a longer shaft than I can cut down. The replacement is 5kΩ instead of 4KΩ, do you think that will be critical?
 

JonCarter

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Apr 18, 2011
Location
Meridian, Idaho, US
I've opened those type of pots. You can usually get away with it once, after that you may find the tabs break off when you bend them again due to stress fractures.
If you can't find a Clarostat 4k linear pot (try Allied Eledctronics), don't bend the tabs more than necessary to open it and when you close it up, just bend them a little then solder them to the top of the pot..

Still looking for gears . . .
 
Joined
Nov 4, 2020
Location
Illinois
I just acquired a Century Lighting Edkotron #281 Control Unit on eBay. Why, you ask. Well, I worked with one in grad school 50 years ago. It is also a historically significant milestone in lighting history; check out Derek's Wiki page for details. The #281 Control Unit is a simple controller with 6-channels and a master supplying a 15 volt half-wave DC signal to the dimmer pack via standard 10-pin CJ connectors. As the photos show, my unit is complete (except that the original on/off key switch has been replaced by a toggle switch) but the paint has completely deteriorated.
As received only the master pot and channels 1-3 are functional, so I plan to completely disassemble and refurbish as much as possible. Oddly enough, I have an original instruction manual for the Edkotron system, which is quite helpful.

View attachment 21872View attachment 21873View attachment 21874
Hi!, I spent many years in field service back in the analog dimmer days. I have all sorts of things still sitting around here. Pretty much all obsolete these days, from pulse transformers to Superior SMRB pots to Major firing cards (I worked for Major for 7 years) to E.C. and Teatronics stuff. It breaks my heart to just throw these things out. The good news is that I have one of those Edkotron control units. The bad news is that it sat outside in a scrap metal pile through a Chicago winter. The good news is that I salvaged the good complete potentiometer assemblies before scrapping the unit. You can have all of it for the cost of shipping. I have also repaired numerous Edkotron dimmers if you have any questions or need individual electronic parts.
 

microstar

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Joined
Jan 19, 2014
Location
Lawton, OK
Hi!, I spent many years in field service back in the analog dimmer days. I have all sorts of things still sitting around here. Pretty much all obsolete these days, from pulse transformers to Superior SMRB pots to Major firing cards (I worked for Major for 7 years) to E.C. and Teatronics stuff. It breaks my heart to just throw these things out. The good news is that I have one of those Edkotron control units. The bad news is that it sat outside in a scrap metal pile through a Chicago winter. The good news is that I salvaged the good complete potentiometer assemblies before scrapping the unit. You can have all of it for the cost of shipping. I have also repaired numerous Edkotron dimmers if you have any questions or need individual electronic parts.
Fantastic! I will send you a PM with my email and shipping address to correspond further. I believe I have actually met you when you serviced some EC bolt-in dimmers here in Lawton.... 1980's maybe?
 

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