For today's pulls I reverted the system back to a steam blocker setup rather than the water filled group version as a test.

I used only the steam blocker on the back of the group
Boiler runs at 1.1BAR for great steaming with the water filled group setup.
No teflon heat break between the group and boiler.
Performance was HOT. Overheating after every shot, long time to cool using the portafilter as a heatsink. To make this work you really need to lower the pressure on the boiler to probably 0.75-0.85BAR and include the heat break. It was slower to heat than a straight to boiler connection though, and almost manageable. By the time I ran the 8th shot through it took quite a while for the group to cool so I reverted to using a water filled cup to suck water into the group and cool it that way.... Definitely not going to work for me.

Worked on a new modification that should be mostly "setup and forget" today, and will document that if it turns out. Again a water filled group method.
My previous group plug would fall out into the boiler sometimes if I didn't check it in the beginning, and it's a mild annoyance which I put up with due to the great temp stability.

Just wanted to point out that some of us that stay quiet are eagerly waiting for every update to this thread. Keep up the good work

I've been wanting to make sure whatever solution I find really works. Today proved how well the water saturated group is working compared to the steam heated version. What was La Pavoni thinking with these 'pre-millenium' models I wonder???

I've been pulling shots of home-roasted Ethiopian Sidamo Natural G4 (lots of picking through those G4 beans!). From where I measure temp I tried pulling the shots with a starting temp of 92.5c and they were spicy - just okay. Changing the start temp to 92.0c I get the most wonderful hazelnut and vanilla shots, and great in cappuccino. Shot after shot the temp stability has given me a new appreciation of this little beast. Running the boiler at 1.1BAR also gives me great steaming capability, while still enjoying the temp stability.

Generally I test load/temp on various beans and roast, and I'm able to dial in quite precisely with the previous setup of the back of group plug to dipper tube. Tomorrow I'm testing a modified dipper tube through the plug to the back of the group for a water saturated group.

Updates will follow.

LaPavoni thinking was a rapid heatup to operating temperature for 1 or 2 quick first coffee of the day before leaving for work.

Then why develop a "16" (8) shot professional during this period which is bound to overheat. Poor design decision I think. They should have returned to the original group style or released the 'millenium' group at that time.
Would have been interesting decision meeting series to listen in on.

Okay, here's the fix for my La Pavoni Pre-Millenium Professional:

-Taking a Millenium version group 'plug' filed down to fit the back of the pre-millenium group, reaming out the thread area to 8mm for nearly all of the center hole, then filing that left area to 7.5mm I was able to tightly fit the dipper tube through that plug.
-Then filing a hole in the top of the dipper tube that extends inside the group cavity, cleaning all brass flakes off of the dipper tube and screwing this into the back of the group, as usual, you now have a group with hot water where steam used to be.
(This could be accomplished with a lab grade plastic cork too. That would be far easier than turning or filing down the millenium plug to size.)

Now when you raise the lever the piston rising will send water from the group back into the boiler, and as the piston lowers it will bring hot water from the boiler to the group. When pulling a shot starting with 92.0c I often see an overall rise of 5-6c. Dropping the PF into cool water, then locking into the group will typically drop the temp back to where I want it in the time it takes to grind and tamp the next basket. Mini pumps of the lever can be used to raise the group temp by 0.2c increments quite easily, and a full pumps will bring it up quicker.

Initial heating of the group does require several pumps of the lever with pausing in between, but that's the price I have to pay for an 8 shot La Pavoni system. Running the boiler at 1.1BAR is perfectly fine, as the group is temp stable, so now you can get better steaming for those cappuccinos.

I also modified the steam valve with a silicone hose, 3mm ID x 5mm OD, slipped over the end of the valve and cut flush. Now about 1/2 turn brings it to max, and the turn off is non-leaking. Got the idea here on HB with mention of power coating hole and bolt cover discussion, but didn't have those handy and the local hardware store had the small silicone hose in stock.

Thermo Probe Placement: Covered by velcro wrap for insulation from ambient. Naked k-probe.


Dipper tube cut show with files used to cut and cleanup the work.


Close up of dipper tube hole.


Steam valve with silicone tubing cover.

And here's a video walkthrough of the modifications:

DanoM wrote:Then why develop a "16" (8) shot professional during this period which is bound to overheat. Poor design decision I think. They should have returned to the original group style or released the 'millenium' group at that time.
Would have been interesting decision meeting series to listen in on.

Simple answer the steam heated group was the standard before the Professional was born. The Professional model was born in 1976-1977 with the only idea of increased boiler water capacity. The present capacity Pro did not arrive until the 78 model year and the earlier were transitions. http://www.francescoceccarelli.eu/lapavoni_pr_eng.htm

Very nice. You are making the 2nd gen La Pavoni group perform like the similar group of a 2nd gen Olympia Express Cremina.

Wish I had a Cremina to compare it with. If anyone wants to send me one in need of repair I'll be more than happy to fix it, test it, and report back.

It has been very temp stable though, and when pulling 8 shots out of the professional that's been great. Higher pressure boiler has really been good for steamed milk too.