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Eureka Eureka Electronic Controller


Registered User
Dec 24, 2014
Bryan Mumford made a controller for the Eureka clock which ensured it kept quartz quality time. I have had one on my No.1 clock for about 15 years and it keeps almost perfect time. Having acquired a No. 6 clock a few months ago I replaced the flag & pin set, cleaned it up and gave the case a bit of TLC. It ran well and reasonably accurately (one or two minutes/day which I could probably have improved) on 1.5v.
I wanted a second controller and experimented with the controller which Frank Roesky (who posts as Praezis on here) offered for the Bulle clocks.
Unfortunately I could not get it to work with the Eureka, but Frank kindly worked on it for me and developed a modified set of code for his controller that drives the Eureka brilliantly. The clock needed setting up ( via the star wheel) to loose a bit on full voltage (maximum arc) and gain as the arc decreased.
My No 6 has now been running on his new model controller for two weeks. It is driven by a pair of 1.2v Ni-Mh C cells in series. It has almost 345 degrees of action and after two weeks is keeping as close to perfect time as makes no difference.
The next question is how long the C cells will last. The same cells in Bryan's controller (his uses three in series) run the No.1 clock for about four months.
Next step is to see if I can fit the controller into one of Carlton clocks Eureka batteries so that it all looks right.
If anyone with a Eureka wants Quartz accuracy, then I recommend Frank's controller.

James McDermaid

Registered User
Apr 29, 2011
I use one of the Carlton Clock #6 fake dry cell (Flag cell for UK folks). I have it adjusted down to a little more than 2 volts. The fake #6 uses 4 "C" cells and I usually get a good year. I made a repo label and slipped it on and it all looks all original.

There is a company making some of the old Eveready batteries that were used in 50''s electronic stuff and I believe they make a real #6 drycell. Excell is the brand I know of. This gives me motivation to get my Eureka running on 1.5 volts.

My Eureka running just on battery voltage runs fairly accurate, certainly less that a minute a week. When the Arizona weather changes it will go either fast or slow and a couple of appropriate turns of the star wheel gets it on time for a long time.

The balance wheel goes about 365 degrees. On the clockwise turn the bar stops at 11:59, and on the anti-clockwise turn it stops at :55. There must be some isochronism going on as it keeps time even when the balance turns less than 360.

I had read about Mumford''s gadget, I figured if it ran too perfect all I wound have to do is wind clocks.