andrewtran Senior Member Joined: 23 Feb 2014 Posts: 1 Location: Minneapolis Expertise: Just starting
Posted Sun Feb 23, 2014, 12:29pm Subject: Low Pressure on Oscar
After reading a ton about espresso (including a lot of posts on this forum), I finally took the plunge and picked up a used Nuova Simonelli Oscar. I've been experimenting with different doses (7-9g for a single shot) and grind sizes (2-4 macro and all the micro-adjustments on a Baratza Vario), but my extraction times are still way too long. About 30 seconds until anything comes out and at least 1.5-2 minutes to get anything close to a 1oz shot. There's also a lot of coffee grounds left over on the screen after each attempt (sometimes even a piece of the puck).
I've tried replacing the grouphead gasket and cleaning the screen. I also backflushed the machine (water seems to only come out of the right hose in the back...). I opened the machine up as well and didn't see any evidence of scaling. I suspect the problem is low pressure from the pump. But this is my first espresso machine so I'm not sure if I'm overlooking another easy, more obvious issue. Any suggestions or advice would be greatly appreciated. Thanks.
plindy Senior Member Joined: 27 Nov 2002 Posts: 79 Location: Seattle Expertise: Just starting
Espresso: NS Oscar Grinder: SJ Pharos Lido HG-One
Posted Mon Feb 24, 2014, 3:10am Subject: Re: Low Pressure on Oscar
Try removing the screen and diffuser plate from the group head and measure the amount of water in 10 seconds. 4-6 oz ? Is the screen just slightly larger diameter than the diffuser plate ? Does the diffuser plate have 4 or eight holes ?
These questions will determine pump delivery to a grounds rather than pod equipped diffuser and screen.
Water from back-flush should only exit from the right side
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