Who Am I

hopalong

Hi Folks,
    My friends call me Tony and like everybody else here I enjoy a good cup of coffee. I brew with an ancient Cimbali Domus made in 2002 and in my limited experience with domestic machines, makes a brew that is difficult to better and the massive cast construction indicates that it will outlive me.
    I roast in a machine that Heath Robinson and myself designed, incorporating a champagne bucket for the beans, an Ozito hot air gun for the heat and a motor off a 1960's photocopier for the stirring. It does a kilo at a time which is more that I can drink and keep things fresh.
    As an aside, I also have a 50L brewery for that other beverage, but that's another forum.
    I joined this forum for selfish reasons as the Cimbali disappeared in a cloud of smoke and a loud pop. It turned out that a large capacitor connected to the pump failed gloriously. I removed the remains and the machine still runs the same. I wish to discover the function of this capacitor and its importance. Perhaps somebody can advise me which part of the forum I should go for advice.
Cheers.

askthecoffeeguy

hey mate and welcome to the group I had a la cimbali m20 for a very long time and it lasted for ever but after taking it camping along with a generator one too many times it lost its sheen a little bit and i couldnt really use it for commercial gigs any more, so I moved it on but it never gave me a days trouble and I serviced it one per yer whether it needed it or not so it was always in top condition cant really answer any technical questions about the machine i had a sunbeam cafe series em6910 that went 'pop' about a week and a half ago - there was a loud banging noise and then everything just stopped working - could probably have fixed it and maybe i still will but I goy a 12 month old machine for $100 - later model version of the same machine, plus i have a modded rancilio epoca single group on the bench at home so i feel like im pretty sorted all the best with your repairs, pat

Koffee_Kosmo

Electrical parts can fail but heat is a big factor, however they are easy to install Without a schematic I can't help with its function in the machine if you can't find an original capacitor from the maker / distributor look for the equivalent uf value and also a 105 Celsius model KK

Brett H

Welcome mate!  Agree with KK. For the longevity of your pump you need to replace that Cap.  Welcome mate!

mycuppa

Welcome. The answer to your question is not so much for a coffee forum but a very simple electrical problem that afflicts literally 95% of all single phase motors eventually, particularly motors that have higher torque duty like pumps. Electric motors operate by creating offset magnetic poles that cause the rotor to spin. Starting this spin process is by far the most difficult task for an electric motor, like the effort to crank something from standstill. This is far easier in 3 phase motors because you have different simultaneous vectors at your disposal. A reason 3 phase motors are more efficient in both startup and eventual lifespan. They can also be built a bit more compact. Single phase motors will generally have one or two capacitors. The first capacitor is used for startup and if it's got a second, smaller capacitor it's function is for power factor correction (which is useful if there are a lot of motors hooked up). The startup cap creates a phase split to enable the windings of of motor to think it's a 2 phase supply for a very short moment, or delay. Once the motor is spinning, the startup cap is essentially redundant as there is usually a centrifigual switch that controls the on and off for the start cap......sometimes you may hear a faint click sound as the motor is slowing after turning off a motor, that's the cfg switch reengaging. Generally speaking, when motors fail with a pop, it's likely the cap has blown......for a variety of reasons, but caps don't last forever. Another cause of a blown cap is the cfg switch stuck on, meaning the start cap is always active. Finding a replacement that has similar ratings is usually simple. Sometimes this caps are on the outside of the motor and in larger motors they are inside the terminal housing. There are instances whereby a start cap can partially fail, or render itself less effective and motors continue to start, but the motor itself can sustain damage as the additional current draw risks burning out windings. The instantaneous load to spin a motor from standstill is a quantum larger than the load at run speed. If a cap is not working then this start load melts winding very quickly and can take out other components in the circuit as well, like expensive control boards. Motors with light loads, e.g. Fans may be able to start.....sometimes they do this slowly spinning until rpm is sufficient to get enough polar momentum. Many bathroom and toilet exhaust fans suffer this problem prior to total failure. Motors with higher loads like short burst pumps should not be used without the start cap as it will lead to motor burnout.

Brett H

Jeff... this is a comprehensive and generously informative post. Thank you so much!

hopalong

Thanks for that helpful information folks, one learns something new every day. I had not realised those capacitors were so important. In fact I did not know that these little reciprocating motors needed one at all. Now I need to find out what size the offending item was, as it was totally smoked and any markings were obliterated.