Journey of Repairing Motor on Quick Mill Vetrano 2B - Page 6

#51: Post by **DaveC** » February 18th, 2023, 6:41 pm

glinskonian wrote:Update: I even went as far as going back to the espresso shop and swapped out the pump they had replaced for a different one. I was pretty sure that the pump they had given me was a dud, but low and behold when I put the new one on today, I'm still getting the same noise!

I'm extremely frustrated at this point, kind of running out of ideas as to what could be causing this and possible solutions...

If anyone has insight as to what else I could check, that would be appreciated.

I only just noticed the thread, read the first post, listened to the noise (which isn't cavitation). I assumed it was the start run capacitor (I don't believe it's just a start capacitor), quickly read through it and saw you didn't change it. Try a known good cap from the espresso shop and it will probably fix the problem.

The cap will make the motor run rough and also run weak. When it goes really bad, the motor usually stalls. If the cap is a problem, you can get one from ebay of the correct value and type (voltage can be higher) very cheaply.

February 18th, 2023, 7:51 pm

I connected an auxillary line to the input side of the pump and the noise/struggle to get to full pressure was still there.
I'll do this for the outlet side also and see if I notice a difference.

February 18th, 2023, 8:28 pm

cyclery wrote:Something inexpensive to try is replacing the rubber insulating bumpers. I have an even older QM Vetrano. One day last year, the motor started to make a buzzing noise and vibration similar to what you're hearing. I took out the motor and ran it on the counter, where it ran quietly. I checked the pump, which rotated smoothly. When I reassembled everything, the machine still made the buzzing noise. The original bumpers felt and looked fine, but they had to be the problem. My old Vetrano's bumpers are under the motor rather than suspending the motor, but the same principles apply.

I found suitable bumpers online for pretty cheap, I think under $10 for 8. After installing them, the machine went happily back to nearly silent operation. It might be worth a try to isolate at least one variable.

Interesting, the rubber mounts look ok but like you said it might be hard to know until they're changed. Although you would think the machine would still get to full pressure with no issue if the problem was related to this.

February 18th, 2023, 8:32 pm

DaveC wrote:I only just noticed the thread, read the first post, listened to the noise (which isn't cavitation). I assumed it was the start run capacitor (I don't believe it's just a start capacitor), quickly read through it and saw you didn't change it. Try a known good cap from the espresso shop and it will probably fix the problem.

The cap will make the motor run rough and also run weak. When it goes really bad, the motor usually stalls. If the cap is a problem, you can get one from ebay of the correct value and type (voltage can be higher) very cheaply.

I actually checked the capacitor yesterday, and it was reading 26 mF (capacitor is rated for 25mF).

Is this capacitor both a start and a run capacitor, or just a start capacitor? I was thinking that the run capacitor might be the issue, but afaik the only capacitor on this machine related to the motor is the one mounted beside it.

February 19th, 2023, 11:35 am

It might well read OK initially which is why the motor starts OK, then runs out of steam. Pretty sure it's a start run cap, but don't like to say I'm 100% certain if I'm not.

The espresso machine motor doesn't need a particularly high starting torque because it's under very little load when it starts. The main load is once it runs up to pressure. There is a single capacitor and if I were designing the motor, I would make it a start run with a value of 30-50mf. A start capacitor wouldn't be appropriate and would require a second run capacitor when it gets disconnected from circuit.

Hence my assumption it's a start/run capacitor (which it's value would also point to). Just try what I suggested, it's quicker.

February 19th, 2023, 1:25 pm

DaveC wrote:The espresso machine motor doesn't need a particularly high starting torque because it's under very little load when it starts. The main load is once it runs up to pressure.

If the OP can post a picture of the top of the capacitor, as well as the specs on the side of the capacitor. That should tell the whole story of whether this is a start/run capacitor. A start/run capacitor should have a minimum of 3-contact points if there is a common ground or 4-discrete contact points.

I respectfully disagree that start up, represents the lowest or lower load of an AC motor. Quite the contrary. Usually start up represents the highest load of an AC motor, until the magnetic field is established. The winding of the rotor is seen as a straight piece of wire, a dead short, if you will, capable of carrying the full current of a piece of wire the gauge of wire used in the rotor winding. Only a literally 'locked rotor', Locked Rotor Amps (LRA), draws more power. However, the inertia of a rotor that is stopped also has to be overcome as well.

For the 1st few cycles before the 'magnetic field' is 'seen' the motor draws current like a pure DC circuit seeing a straight piece of wire, which is why lights can dim at startup or breakers can pop when that side of the AC line's voltage can drop from excessive current draw.

Hope this is not too far into the weeds.