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Is anyone using voltage to control Vibe pump pressure instead of OPV?
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Discussions > Espresso > Espresso Mods > Is anyone using...  
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Frost
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Frost
Joined: 26 Jul 2007
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Posted Thu Aug 16, 2007, 2:20pm
Subject: Is anyone using voltage to control Vibe pump pressure instead of OPV?
 

I've read alot on the forum about how the 15-16 bar vibe pumps can make it difficult to pull a good shot because the pressure is too high without some form of regulation. The most commonly used approach is to use the Over Pressure Valve to bleed off excess pressure above 9-10 bar.   A good machine with a decent OPV seems to work well with this approach but a bunch of machines (ie: my Gaggia Espresso) either has no OPV or the design in many cases is intended for a safety release to prevent damage only and regular use is likely to result in a leaky OPV (unless upgraded to a better quality).

I had come across a discussion some time ago about using a Variac to regulate the Vibe pump pressure/output and it occurred to me that perhaps, after characterizing the pump/pressure/volume behavior on a specific machine using a variac to contol the pump, you could install an appropriate resister inline to the pump and achieve the voltage drop to get the volume/pressure drop needed.

While this approach would still be sensitive to shot volume ( would change pressure for single vs. double) it would not be an issue for me (it's double or nothing). Also it would seem you could arrive at a better compromise between singles and doubles than what is delivered with a 16bar pump running full open....

Anyway, I'm curious if anyone has tried this approach and could help me save time in investigating behavior of the vibe pump at various voltages other than 120V? My searches here have not turned up anything.

As a side note, I noticed the pump in the Gaggia is rated for 110V 50-60hz while my line delivers a full 120 across the terminals.
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PaulTheRoaster
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PaulTheRoaster
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Posted Thu Aug 16, 2007, 3:29pm
Subject: Re: Is anyone using voltage to control Vibe pump pressure instead of OPV?
 

If you do a google search for "variac vibe pump" there are a few places where people report success with that.

Calculating the right resistance value will be a little tricky. A vibe pump is an electromagnet and a diode. I am not sure if there is a good way to measure the actual current or power it draws with a regular multimeter. But there might be a few ways around that.
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Frost
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Frost
Joined: 26 Jul 2007
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Location: Sierra
Expertise: I love coffee

Espresso: Isomac Venus
Grinder: Lelit PL53
Roaster: Poppery I w/variac, MET, BT
Posted Thu Aug 16, 2007, 5:43pm
Subject: Re: Is anyone using voltage to control Vibe pump pressure instead of OPV?
 

Thanks Paul, re: the diode, that explains the extra pump connections and meter readings I got. I gleaned enough from my searches for proof of concept so full speed ahead I went through my parts bin and found a 10ohm 10 watt resistor and stuck it in there: voltage across the pump dropped from 120 to 110 volts.  (what luck for seat of pants!) I have no way to check actual pressure on this thing yet. I will give it a couple days running (I know this machine too well by now) to see how it effects shot pour and taste. The pump is just a bit quieter too.  I was mistaken on the pump spec: it says "110/120V 60Hz 55 watts" so I'm still within operating spec and should not be dissipating too much current through the resistor.
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jim_schulman
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jim_schulman
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Posted Fri Aug 17, 2007, 9:20am
Subject: Re: Is anyone using voltage to control Vibe pump pressure instead of OPV?
 

I would suggest a dimmer and a pressure meter.

 
Jim Schulman
www.coffeecuppers.com
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Tex
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Tex
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Posted Fri Aug 17, 2007, 9:34am
Subject: Re: Is anyone using voltage to control Vibe pump pressure instead of OPV?
 

OK, I acknowledge up front that I'm the last person that should ever say this, but why are you attacking a pressure problem by reducing the pump's capacity? It's a straight forward proposition to install a Gaggia Classic OPV in your Espresso for ~$20. Is there a particular reason for attacking the problem via the pump?

Good luck!

Tex: OPV.jpg
(Click for larger image)

 
Tex
--
http://www.tinyurl.com/mb4uj - My coffee pages.

http://www.tinyurl.com/2tnv87 - My 'Guidelines For Newbies' page.

http://www.tinyurl.com/2cr3e2 - I sell things for friends & neighbors here. Can I list something for you?

http://www.tinyurl.com/235dfr - BUG is Bunn User's Group (espresso)
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Frost
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Frost
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Location: Sierra
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Espresso: Isomac Venus
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Posted Fri Aug 17, 2007, 2:34pm
Subject: Re: Is anyone using voltage to control Vibe pump pressure instead of OPV?
 

In a word Tex: K.I.S.S.  Yeah, I read that thread about retrofitting the OPV.  I almost  get simple and straighforward out of it. Just a few complications. Is there someone that  has that valve in stock now? I can't put the machine out of commission until at least monday when I get a Venus. Gotta have the morning Capp. I will be stripping down the Gaggia after the Venus is on line. I have to peek in the boiler to see how much bigger it has gotten with all those little black chunks it's been blowing. I may look at doing something different about the overpressure situation then... or I may loose interest from using the Venus.

I did get a noticable improvement in the morning shots just dropping the voltage from 120 to 110 though. It took me all of about 20 minutes of risk free, no leak modifications to try it.  As Jim suggests I do need to get a reading on pressure though to know what I'm doing, but one thing is for sure: it is a step in the right direction.
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Tex
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Tex
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Posted Fri Aug 17, 2007, 2:49pm
Subject: Re: Is anyone using voltage to control Vibe pump pressure instead of OPV?
 

Frost Said:

In a word Tex: K.I.S.S.  Yeah, I read that thread about retrofitting the OPV.  I almost  get simple and straighforward out of it. Just a few complications. Is there someone that  has that valve in stock now? I can't put the machine out of commission until at least monday when I get a Venus. Gotta have the morning Capp. I will be stripping down the Gaggia after the Venus is on line. I have to peek in the boiler to see how much bigger it has gotten with all those little black chunks it's been blowing. I may look at doing something different about the overpressure situation then... or I may loose interest from using the Venus.

I did get a noticable improvement in the morning shots just dropping the voltage from 120 to 110 though. It took me all of about 20 minutes of risk free, no leak modifications to try it.  As Jim suggests I do need to get a reading on pressure though to know what I'm doing, but one thing is for sure: it is a step in the right direction.

Posted August 17, 2007 link


Firm believer in the K.I.S.S. principle myself - not a bad place to start from. However you get there, the pressure does need regulating in the Gaggia. I'd never considered doing it your way, but if it doesn't harm the pump in any way it sounds like a simple enough solution.

BTW: the OPV was available from an Italian source via eBay. Check with Susan (SJM) for more details.

Good luck!

 
Tex
--
http://www.tinyurl.com/mb4uj - My coffee pages.

http://www.tinyurl.com/2tnv87 - My 'Guidelines For Newbies' page.

http://www.tinyurl.com/2cr3e2 - I sell things for friends & neighbors here. Can I list something for you?

http://www.tinyurl.com/235dfr - BUG is Bunn User's Group (espresso)
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SJM
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Joined: 17 Nov 2004
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Posted Fri Aug 17, 2007, 3:21pm
Subject: Re: Is anyone using voltage to control Vibe pump pressure instead of OPV?
 

Tex Said:

BTW: the OPV was available from an Italian source via eBay. Check with Susan (SJM) for more details.

Posted August 17, 2007 link

'Xackly right,

http://stores.ebay.com/ItalianCoffeeShop

except for the price which was $49 and change including shipping (ITALY to CA).  

Susan
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Frost
Senior Member
Frost
Joined: 26 Jul 2007
Posts: 2,070
Location: Sierra
Expertise: I love coffee

Espresso: Isomac Venus
Grinder: Lelit PL53
Roaster: Poppery I w/variac, MET, BT
Posted Fri Aug 17, 2007, 4:19pm
Subject: Re: Is anyone using voltage to control Vibe pump pressure instead of OPV?
 

Thanks for the link Susan. Did you get yours installed ok?  For $49 I think I'll hold out for a domestic supplier or continue with the 50 cent voltage drop resistor approach. Gaggia is about doing it on a low budget and this thing might be asking me for a $50 boiler when I open it up.... hoping I can just clean it up and replace the gaskets.... getting a slightly larger boiler out of the deal ;^)
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SJM
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Joined: 17 Nov 2004
Posts: 1,706
Location: CA
Expertise: I love coffee

Espresso: SAMA, Gaggia Classic
Grinder: K-10PB, Rancilio MD-50
Vac Pot: no like
Drip: no like
Roaster: HotTop
Posted Fri Aug 17, 2007, 4:37pm
Subject: Re: Is anyone using voltage to control Vibe pump pressure instead of OPV?
 

Frost Said:

Susan. Did you get yours installed ok?  

Posted August 17, 2007 link

Okay, okay, my Achilles heel:  finishing projects I start.  Blush.  It's still sitting in the drawer waiting for me to find out where my get-up-and-go got-up-and-went to.

BUT, Prav did get his installed, and you can see how pleased he was with the results if you check towards the end of this thread:

"Does new Gaggia Coffee have an adjustable OPV valve?"
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