CrackAddict Senior Member Joined: 7 Apr 2005 Posts: 8 Location: London, UK Expertise: I love coffee
Espresso: Expobar Grinder: Minoka Roaster: iRoast
Posted Tue May 3, 2005, 6:57am Subject: Re: Adjusting vibe pump pressure on HX machines
A note that may help some Expobar neophytes like myself.
The pressure adjustment (in my Office Control) is a white plastic screw inside a brass three-way fitting on the outlet of the vibe pump (red plastic inside a metal holder).
It's about a 1/4" screw with a very fine slot - most screwdrivers wide enough to fit across will have a blade too thick to fit in the slot. You may want to file down a cheap stubby slot screwdriver for adjustments.
My "shipped" pressure was almost 14 bar (measured with a portafilter gauge). I have turned it down to 10 (about 1.5 turns counterclockwise) and will report on the results later.
I also followed the suggestion to reroute the overflow back to the reservoir as I live in a very hard water area and use Volvic bottled water in the machine. Supposedly Volvic is soft enough to minimize scaling problems.
Confusedguy Senior Member Joined: 16 Apr 2005 Posts: 78 Location: California Expertise: I like coffee
Espresso: Gaggia Carreza Grinder: Rancilio Rocky
Posted Tue May 3, 2005, 3:23pm Subject: Re: Adjusting vibe pump pressure on HX machines
When I tried to adjust the pressure down on my Quickmill Eliane, I found I had to back the threads almost to the point where where the fitting came off. I removed the nut and spring and and filed down the end of the spring, probably less than a mm. I was then able to get the desired pressure (9.5) without risking the screw falling off. I agree that the adjustment is non-linear. Originally mine was up at about 16! Russell
mayong_md Senior Member Joined: 12 Feb 2011 Posts: 25 Location: Bacolod, Philippines Expertise: Just starting
Posted Fri Jul 6, 2012, 7:45am Subject: Where is the OPV on a Grimac Mia ELE?
]]Hello. Sorry to revive an old thread.
I got to reading about brew pressures and HX machines, and found this thread.
I have a Grimac Mia Electronic version. I decided to open the machine to try the OPV volume runoff method of "estimating" brew pressure. I locked a blind PF and turned on the brew button. The pump came on, after 6-8 sec, the pump became quiet as it labored through the blind PF, the beeping - with a flashing light from the brew button. After 20-25 sec of this beeping, I decided to turn the brew button off. I did NOT see water coming out of the return to tank hose. From the readings, it was mentioned that if little (<2oz/25-30sec) or NO water comes out, then the OPV was adjusted high from the factory.
I looked for the OPV, taking note of the pics of the different OPVs of different machines. I found a pic from the La Valentina - a Grimac Machine, I believe, and used this as a guide to identifying mine. I followed the outflow tube, and the tube was attached to this:
Instead of just a barrel, several fittings are seen attached to a brass block. The outflow tubing attaches to this block as well. I don't see the nut I need to adjust to release pressure. Behind the block, in this pic, is a sort of switch. Maybe a pressure sensor that sets off the beeping when pump pressure is exceeded?
Hope you can help me identify where the OPV is in the MIA.
lotusblackbox Senior Member Joined: 7 Jul 2012 Posts: 11 Location: Sydney Expertise: I love coffee
Posted Sat Jul 7, 2012, 9:23am Subject: Re: Adjusting vibe pump pressure on HX machines
It's beginning to sound like the dream machine not only has perfect temp stability with the ability to set a desired temp but also a controled ramp down of extraction pressure. Also with the ability to set a pressure profile.
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