P.S. I don't mean to contradict what Peter said, only to point out that the pump should hold some particular pressure, regardless of grind, for each shot. That particular pressure will be at or below the pressure set with the opv--so if the grind is close to a decent shot, you'll hit the max pressure. If the grind is really loose, the pump should build to some pressure below that max and then hold that. In my experience at least, the indicated pressure shouldn't fluctuate after it builds to its level for that shot.
In your case, I think the pump builds to 10 and then the opv opens. It sticks, allowing pressure to drop to 7. The pump revs up against less resistance. Then at around 7, opv closes again and the cycle repeats. b Sent from my C-Dory On Mar 11, 2011, at 13:17, Ben McCafferty <[email protected]> wrote: > Even easier, put in a blind pf and see if it holds something like 9 bar > consistently, or if it moves. > > Max brew pressure on the gauge is based on how the opv is set, so it will > hold stable pressure against any grind/distribution if the opv is working > well and the pump is not worn (though that pressure may be low if the grind > is really loose). > > My guess is that your opv is sticking, and when it sticks open the pump runs > faster because it has no resistance. > > Try this. Unscrew the opv adjusting screw all the way and remove it. (behind > the drip tray on the right--no pressure on the pump before you > do this!) Look for crud, i.e. mineral deposits and clean them up. Carefully > remove the black rubber puck on the end of the screw, flip it over, > reinstall. Then replace the screw and use your blind pf to set pressure to 9 > bar or so. Then try pulling some shots and see if the problem is resolved. > The opv will eventually need to be replaced, but flipping the puck will buy > you many months of service. If it's sticking, that's another story and you'll > probably need a new one sooner. Curious to hear the outcome! > ben > Sent from my C-Dory > > On Mar 11, 2011, at 13:01, "[email protected]" <[email protected]> > wrote: > >> If the brew pressure gauge is measuring resistance, then it might be a >> tamping and/or grind issue. Does it do this consistently, or only >> occasionally? If the latter, then I might suggest experimenting with >> different grind, diostribution, and tamping techniques to see if that >> makes a difference. >> >> Pete >> >> On Mar 11, 1:28 pm, jpaul <[email protected]> wrote: >>> Hi, >>> >>> Just acquired a used Brewtus II in great shape and I'm excited to be >>> moving from my 6 year old Pulser to a real double boiler. It does >>> have a problem with brew pressure swinging around during extraction. >>> This was known by the previous owner who described exactly what I'm >>> witnessing. >>> >>> Once the pump has been engaged, the gauge reads around 7 bars and then >>> it'll hop up to 10 bars momentarily and then back to 7. As it moves >>> from 7 to 10 I can hear the pump get more lively as if more amperage >>> is being afforded to the pump. >>> >>> This sort of feels like a control box issue but I wanted to throw it >>> out there and see what folks think. Can the control box vary voltage/ >>> amperage? >>> >>> Thanks much for your advice and counsel. >>> >>> JPaul >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Brewtus" group. >> To post to this group, send email to [email protected]. >> To unsubscribe from this group, send email to >> [email protected]. >> For more options, visit this group at >> http://groups.google.com/group/brewtus?hl=en. >> > > -- > You received this message because you are subscribed to the Google Groups > "Brewtus" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/brewtus?hl=en. > -- You received this message because you are subscribed to the Google Groups "Brewtus" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/brewtus?hl=en.
