If the pressure goes to 15 bar and there is a gauge you can see, to make it work now, you need to start making the grind coarser till you get max pressure to 9 bar. Many of the vibe pumps were designed to run at 9 bar to make a "typical" espresso. If that's the case, you might also need to disable the pre-infusion as much as you can. Other than that, add an OPV valve to limit the pressure to 9. It will likely be a faster shot and you will be limited in what you can do, but it might work.

SandraF wrote:You need fresher beans.

Lots of tips offered, but no amount of tinkering will result in a "good" shot if the beans are too old. Get freshly roasted beans & wait 5 days. See if that helps.

OP said they were using week-old beans, so I don't going freshness is an issue. I've pulled beans up to a month old and haven't experienced channeling on them.

If you don't mind tinkering, there's a guide on how to adjust the OPV setting to drop your max pressure limit down to 9 bars:

What about now

May I assume there's nothing wrong with my prep and beans ?

luckydragon wrote:

thank you !

for easier reference, here are the useful links:

Over Pressure Valve Upgrade

Stock OPV adjustment

ifeghali wrote:What about now


video

May I assume there's nothing wrong with my prep and beans ?

Nicely done!

Looks great, what was the final step that made it work?

by pulling in pre infusion mode only (where pressure is usually around 8 bar). its good enough for me but in the name of science I might take the next steps to see what happens:

1) puck screen
2) shower screen upgrade
3) as a last resort if (1) and (2) don't work: OPV upgrade

It's unlikely that a puck screen or shower screen will help. If taking it out of pre infusion means the pressure gets over 9, figure that out first, but if it gets to 8 in pre-infusion mode, I'd just do that and work on what kind of coffee you like and what grind size adjustments do? There is nothing wrong with limiting brew pressure to 8bar.

I agree with ira; puck and shower screens aid with water distribution, but your issue is that your pump pressure is too high, and the screens will not provide sufficient resistance to lower the water pressure at the puck.