Paolo_Cortese Yes, we talked about the HX two years ago. The steam boiler is not filled completely with water, hx shouldn’t be broken.
I don’t know how but I’m 100% sure steam pressure is affecting the brew circuit. I can not explain from where or how but it’s happening for a long time. Steam boiler off the machine runs smoothly. Steam boiler under pressure, tha machine does not run smoothly. I’m sure is a “physical” thing and no an electric issue because once the coffee profile “breaks” this 2 bar obstacle, it will be fine in the next shot without cooling down the service boiler. A friend lives nearby and I can tell his machine does exactly the same:
Steam boiler hot, above 125-126º. Pull a shot and it stops at two bars, pump struggles and overshooting happens. Clean pf, grind coffee, tamp, pull a second shot (steam boiler at 128º) and it’s like the 120º video. The pressure builds smoothly up to 2,5 or 3 bars, stay here during preinfussion and goes up to the expected pressure, no overshooting.
I know this can sound strange but believe me, this is what is happening for years with these machines.