Magister Stella Pro brew pressure variation

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#1: Post by afranco »

I recently got one of this machine from idrinkcoffee, so far it's been awesome, but I notice something that to be honest I have no clue if it is normal.

During the process of taking a shot, the pressure gauge don't keep stable, it's not only decreasing, but keeps coming from 9 to 8.5 bars, a couple of times, and this follows the heating element, for example, every time during the shot that the heating element turn on, the bars goes down, and vice versa.

Someone know if this is normal, or affect the quality of the espresso?


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#2: Post by Jeff »

It sounds to me like it's related to load on the electrical circuit in your home. Is the machine the only thing on the circuit when it's running? No electric kettle, toaster, pancake griddle, egg steamer, or anything else running in the kitchen at the same time? (There's often lots of outlets on one circuit.)

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afranco (original poster)

#3: Post by afranco (original poster) »

There are others appliances connected on the same circuit, but all of them are turned off during the shot.

Found this video on YouTube and it's similar on what is happening to mine.
Thank you


#4: Post by JRising »

All vibe-pump machines will do this to some degree.
Of course it depends on the gauge of the power cord, internal wiring, household wiring, etc.

The gauge is working. When the draw of the element is weakening the stroke of the pump, the pump will move less water per stroke. The resistance to flow isn't increasing through the puck so pressure drops slightly.

Everyone who claims you can't tell the difference between rotary pumps and vibe pumps in the cup are claiming you won't notice the effect this drop has.

Someone came up with a rather clever idea using a diode to eliminate this issue, I can't remember exactly what it was, but it uses the pump circuit to half-phase the element so it's still half heating but the pump is getting all of its half-phase (it's only using that half anyway, it has its own diode). That was in the thread where someone claimed that the amp draw of the heating element was interference caused by the PID.
Electrical Issue- PID controlled equipment causing interference

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#5: Post by HB »

JRising wrote:Someone came up with a rather clever idea using a diode to eliminate this issue, I can't remember exactly what it was, but it uses the pump circuit to half-phase the element...
See Pressure Perfect with Vibe Pump.
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#6: Post by Nunas »

As others have said, this is normal, due to voltage sag. Incidentally, it wasn't easily noticeable until manufacturers began to put PIDs into HX espresso machines. Pressurestats have a dead-band, which causes them to switch on and off less frequently; so you only see the bump once in a while. Sometimes, on my older Stella I'd pull a shot and not have the heater come on at all. PIDs are usually adjusted to have a much smaller dead-band, making the slight change in pressure more noticeable due to the frequent switching. There may be a setting in your PID where you can change this, but I don't know where it is. If you mess with your PID settings, be sure to write down the original ones, or know how to do a factory reset :lol:

afranco (original poster)

#7: Post by afranco (original poster) »

Hey guys,

Thank you so much for all the detailed explanation on this, since this is my first "serious" espresso machine, I thought that this unit maybe would be defective, so before run to the store that I bought, I thought a good idea to come to you guys first and have a better idea.

Thank you so much!

I will not do nothing about it, since that is hard or even impossible to me notice any difference on the cup, I was just concerned if it was malfunction.

For this week, planning to change the shower head and filter basket, IMS shower head and VST filter basket, do you guys think anything else that can increase the consistency of the shots? Maybe next month I will buy an EricS Thermometer.

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#8: Post by Nunas »

On an e61 HX machine a brew group thermometer will make a huge difference in consistency. I put an EricS one on my Stella PRO thinking I'd leave it on only until I got used to the machine. I never took it off and used it always.
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#9: Post by Jeff »

I agree that an EricS thermometer is probably the best, first step.

In my experience, VST and other high-flow baskets tend to accentuate imperfect puck prep and probably grind irregularities. If you want a "precision" basket, I'd start with the EPNW HQ 14 (doses like an 18, if you can get it at an affordable price delivered into Canada). I'm not sure that expensive shower screens dramatically improve in-cup quality. I don't consider "nanocoating" to be an advantage.

I'd also go for a good, WDT tool. I prefer the LeverCraft one, but some 0.4 mm or finer acupuncture needles in a cork are very good, at a more modest price.

If you don't already have a scale that reads to 0.1 g, that's an essential part of getting repeatable results, in my experience. There are several around US$15 that are suitable.

afranco (original poster)

#10: Post by afranco (original poster) »

Awesome, thank you so much for the tips.

The only thing that I am still looking for a thermometer it is because these plastics one I found kind of ruin the beauty of the machine, so I am trying to find one that is more pleasant to look at lol

Good to know about the rest, the only thing that I already got was the screen shower, its because besides the fact about getting a better shot, it was told me that it is way easier to clean up. idk.