Announcement

Collapse
No announcement yet.

La Pavoni undressed

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • La Pavoni undressed

    Here she is in all her glory. Ive pulled a few things off and it looks pretty good inside. Theres definitely scale, but the level is pretty low, consistent with running with filtered water. Ive seen far worse. In fact I drained the boiler and the boiler drain absolutely gushed out. This means that the scale build-up is reasonably light. The water from the boiler smelled like wet carpet, but was completely clear. I also drained some water from the heat exchangers and it too was clear and tasted completely neutral... This is a good sign that the machine hasnt been too abused in its past life. The groups are great. They are La Pavonis version of an E61 group, but the shower screen is held in with a screw and is easily removable. The water dispersion block is a two part affair. There is a large amount of empty space in the head of the group. This is very different from the Bezzera group, which has very little empty space. The most unexpected thing about this group is that when I worked the dispersion block loose, the group seal actually came out with one of them, it remained in the other, but was easily dislodeged with fingers. Now I have both group seals out without having to recourse to an icepick/screw driver type brute force and destruction. Ive been on the alert from one of these Pavoni groups for just this reason. Ive heard some stories about major struggles in getting the seal/shower screen out of a standard E61 group, and this was one of the reasons I avoided.

    The photo is a collage of images, showing the front twin E61, the rear nickel plated 14l boiler, under the group heads with the gasket and dispersion blocks removed (not too dirty at all, but still in need of a clean) The insert in the red box is the rusted pump. Thats the one item that isnt in working condition. I suspect one of the E61 microswitches is also cactus, but thats minor. The motor does run, but there is a bit of bearing noise. I have another nearly identical motor which Ill probably use in its place, although Im sure itll run as is.

    Ive popped the top of one of the E61 groups and its pretty clean inside. Some scale build-up but again rather minor. Im sure that I could get it up and running without a major descale, but it might be worth getting it back to spotless condition before running it. Im still debating this one.

    Anyway, Im pretty happy with the machine. The seller has agreed to reimburse me a large portion of the cost for a new pump, so the machine will have cost me $520 plus pump. Restoration costs might not be too high, but the E61 groups are rather expensive groups to refurb. Ill see how it goes.

    I cant wait till I pull my first shot on the beast.

    On a sad note: The BZ35 has pulled its last shot. Im going to clean it up and sell it off to finance the new machine and some of the refurb. The farewell was about as good as it can get. It was a tight ristretto with a light tamp. The espresso just dripped out with a beautiful red colour... just what I was after.
    After about a year and a half, Ive really learned to drive this machine. With care, its shots are as good as anyything out there. Its solid as hell, easy to work on and is built with commercial quality components and it steams like a demon. I think Ive come full circle with the steaming as Im back on the 4-hole tip and happy as hell. Soft silky microfoam every time and only about 8-10 seconds required for a single cups worth....

    Oh well, on with the Pav restoration... the lack of coffee will drive me... ;D

    Cheers,

    Mark


  • #2
    Re: La Pavoni undressed

    Mark,

    She looks good - really good. You have done well!

    Id say refurb wont be very expensive judging by your description and the photos..... maybe just seals, group filters etc...

    If it were me - Id do a full refurb.... she certainly is worth it!

    You have yourself a very attractive piece of kit!

    Comment


    • #3
      Re: La Pavoni undressed

      Sure is [smiley=thumbsup.gif]

      Mal.

      Comment


      • #4
        Re: La Pavoni undressed

        Heres an update. I finally had her dressed a few days ago and got her up and running.

        First things first.

        I pulled her down to the frame. All the pipes were easily removed by gently tapping the compression fitting nut to crack open the seal. Each pipe was individually descaled in citric acid solution until it looked like a tube of pink salmon.

        The boiler was more difficult. I removed the entire unit. It is a closed boiler (unlike most commercials with an end-plate), so access is only via the various holes. The element screws in and I took the entire boiler to a coffee tek place to have it descaled. Unfortunately they werent able to do the descale, but did remove the element for me. So I went to super-cheap and bought a 40 l bin which was a good fit for the boiler. I used the bin to descale the boiler and HX units. The boiler actually wasnt too badly scaled in any case. I let it sit in the citric acid solution overnight and then rinsed it and soaked it in fresh water to try and get rid of any acid residue. I also descaled the element by fitting a baloon over the element terminals and dropping the entire thing in the acid bath.

        I also removed the steam and hot water wands and cleaned/descaled them. I bought new seats for all the wands from coffeeparts (overnight service is awesome). I didnt open the valve bodies, as unless theyre leaking, I could see no reason to do so.

        I also got really intimate with the two E61 groups. To open these up requires a 36mm spanner, so I had to buy one. I actually bought a 1 7/16" spanner which is 0.5 mm too big, but is the size needed for the element. In any case the slight size difference is negligible at this size.

        For the E61s I did a descale in citric acid as well as a soak in caustic soda to remove any residue in the brew path. This cleans them up really well. I did the caustic soda soak first followed by the citric acid soak. I also had to recondition the three valves in each group. Again coffee parts came in with the valve seats. I also needed some pins that had been worn down by the cam. I got the pins from coffeeparts but they had the wrong thread!!! So I had to work around this. Rather than try to tap the correct thread, I went and bought the valve seats and a few other pins and built up entirely new valves. To save some money, I ordered some pins that I knew were the wrong length (too long) and shortened them to the correct spec in a lathe.
        After all that it was time to put it back together again.

        As for the dead pump, I decided to use one Id been running for nearly a year as an outboard pump.

        So that was everything. Then to put it all back together. No real drama. I only wired in two of the elements to drop the current draw to a manageable 12.5 A.

        Once I got it back together I fired it up and waited.... It looks like the pressurestat was set to 1.1 bar, which is pretty standard. Both pressure gauges worked, which is good. The pump that I had set to 9 bar read 9 bar on the Pav gauge. The boiler filled in no time, using about 7-8l of water (theres plenty of head room for steam).

        The groups use thermosyphon restrictors to keep the group temperature from overheating (3mm apertures). The group heads reached between 91-97oC. The fluctuations due to the pressurestat cycle. Ive already decided to PID this away in the near future.

        I loved how quiet the thing runs. The rotary pump is/was very quiet and the loudest sound is the Sirai pressurestat switching(clunking). But these are 30A switching monsters.

        A pressure check to make sure all the fittings were tight revealed a leak in one fitting. This wasnt a tightening problem, so probably meant some damage on the seat of the compression fitting or the olive. I noticed the leak was via the threads of the compression nut, so a few winds of teflon tape and viola, all tight and no leaks since.

        As soon as I was satisfied I got me some beans and went to work. I made two straight shots. The first was too light, under xtracted. The next was awesome. It hit the red crema zone and came out with caramels and sugars detectable in the rather old beans. Then a couple of cappas. The first was very smokey... I burnt the milk. Man this thing steams fast compared to the BZ... maybe 5 secs for 200 ml of milk. The next was better, but the shot was off. However there was still a taint in the milk due to the descale of the boiler. Ive since refilled the boiler a couple more times, but before I could taste some more of this red crema madness, the pump died...(it started going very squeaky and the pressure was fluctuating). I have yet another pump, which I tried, but this one was also cactus (worn seals couldnt get up to pressure). I also tested the motors (I have a couple) and they were fine. So its off to buy a new pump before this machine can be brought back to life again.

        Then I noticed one more thing. The seals around the lever rod leaked when using a blind filter basket. It looks like another coffeeparts order is about to take place....

        So there it goes. All the really important parts run fine. But the pump will cost me a new replacement pump.

        Ill also add PID control of the boiler temperature pretty soon, as Id like to limit the fluctuations in the group temperature.

        Cheers,

        Mark.

        Comment


        • #5
          Re: La Pavoni undressed

          Mark....

          When you say:

          The groups use thermosyphon restrictors to keep the group temperature from overheating (3mm apertures). The group heads reached between 91-97oC. The fluctuations due to the pressurestat cycle. Ive already decided to PID this away in the near future.

          Im a little (actually a lot) surprised you blame the pressurestat cycle. :-/

          It sounds to me more like variation in the thermosyphon than boiler temp variation.

          My pressurestat has an on/off hysteresis of about 0.15 Bar .
          Now if we assume it is 0.2 Bar that equates to a temperature variation of less than two degrees Celsius........ (from my BP temperature / pressure graph.)

          So unless your pressurestat is wildly off.... it should be maintaining pretty close to what you would get from a PID (infact I thought PIDs are only used on the brew boilers of machines like LMs - the pressurestat being sensitive enough for single boiler HX machines).

          Comment


          • #6
            Re: La Pavoni undressed

            Looks like all is going really well!

            Like JavaB says, Id be surprised if the temp fluctuation were solved by PIDding it ... you did descale the thermosyphon, right?

            Just a few ideas, presuming that the group is very similar to an e61; how about replacing the 3mm thermosyphon restrictors with 2mm restrictors? That should be enough that it doesnt mess with your preinfusion, but it will lower the group temp relative to the boiler so that you can crank the boiler up and cut your steaming time to four seconds instead of 5 ;P More importantly, seeing as the preinfusion restrictor is so easily accessible, you could have one 0.8 and one 0.6 for the hell of it. Of course, if its plumbed in, I guess that youll be able to regulate the preinfusion using the middle position of the lever anyway. Im sure that you have seen the M6 thermocouple adaptor.

            If you want to PID the machine, you might find that running the PID off a pressure transducer eliminates the headache of trying to work out where to put the thermocouple!

            Sounds like youre going to have a blast with this machine.

            Luca

            Comment


            • #7
              Re: La Pavoni undressed

              Good to see that the problems were little manageable surprises rather than shocks, Sparky.

              Dont you just love that salmon copper colour? Its almost a pity that it has to be hidden by the panels!

              Good luck with the pump. Any chance you can rebuild it yourself?

              -Robusto

              Comment


              • #8
                Re: La Pavoni undressed

                The temp variation is real. Ive been monitoring the boiler wall and there is a 6.2 oC variation during the pressurestat cycle. I havent checked the steam charts yet, but if Java is correct, then the Sirai pressurestat needs an overhaul. Thats one of the things that I didnt do during the refurb. Membrane kits are available for coffeeparts, so its no drama. My boiler pressure gauge isnt calibrated below 1 bar, so the low point may be quite a bit lower than the 1.5 bar deadband that JavaB has.

                Luca, firstly its a real E61, just with a different shape and an easily detachable shower screen (OK slightly different). Otherwise its parts compatible with the E61. As for the gicleur, it has 0.7mm ones fitted and they give a really nice flow, so I dont see the need swap em about. Also the E61 has a pre-infusion chamber, which seems to work pretty well. No need to "middle position the lever", which is not really possible anyway as the microswitch is actuated pretty much as soon as the top valve is opened by the cam.

                As for the high group temp, the water dance from the group seems to go on forever. Thats telling me to lower the pstat first. Once thats happening (given the pstat is operating correctly) then Ill revisit the group temp. If it is still too hot, even when the water dance is manageable, then its time to look at 2.5 mm thermosyphon restrictors, which Ill probably make myself, as I love the DIY stuff on the lathe.

                Im aware of Eric S M6 thermocouple adaptor, thanks. Its a mod for down the tracks.

                PID with a pressure transducer is definitely the go, if a cheap transducer can be sourced. I know of one supplier and might look that up again. JavaB, there are PIDed commercial HX machines currently available, such as the Reneka that Pioneer Coffee recently bought. It may not be the best use of a PID, as you suggest. Again, Ill check the pstat operation first.

                Yeah, Robusto, no show stoppers yet. I do have a sticking anti-vacuum valve though and the possibly dodgy pstat (that can be refurbed for cheap) and now my latest pump seems to have completely gone caput. It was getting up to 8 bar this morning, and now nothing.... New pump coming.

                Yeah its all fun if you like that sort of thing. I was just tantalised by the  momentary operation of the beast before the pump upped stumps on me....

                Cheers,

                Mark.

                Comment


                • #9
                  Re: La Pavoni undressed

                  Mark,

                  Sounds like the procons were a bit old and tired..... they have a reputation of being excellent pumps - even happy to draw from a reservoir.

                  I was amazed at the capacity of the La Cimbali pump - greater than most 4 group machines..... but it certainly comes into its own when you are extracting from both groups and the autofill cuts in..... the group pressure barely moves from 9 no matter what I do. They certainly have over engineered the machine (which aside from the weight - Im real happy about).

                  Sounds like your restoration is really going very well- with only a few minor annoyances along the way - as there always are.

                  According to my chart with a total pressure of 1.9 Bar BP is 119C and at 2.1 Bar it is 121C ..... and my boiler varies from 1.1 to 0.95 above atmospheric.... so only 0.15 dead band- which should give <2 deg C variation.

                  It will be interesting to see what the dead band on your is... 6C variation is approximately 0.4Bar variation around 1.1 Bar...... mmm me thinks overhaul time for the pressurestat!

                  Comment


                  • #10
                    Re: La Pavoni undressed


                    Yep 0.4 bar looks to be about what Im getting. I was going to overhaul the sucker, but thought Id suck it and see. But it is usually recommended that you replace all the rubber parts on an old machine, and that includes the pressurestat membrane.

                    A few other things have popped up. One of the thermosyphon lines is now leaking. I think this is just a case of a few thermal cycles loosening up the fitting. Ill retighten and see. Otherwise zi noticed the large relay that switches on the element seems to be humming. Im not intimately familiar with relay failure, but audible humming from the switching coil doesnt sound right.... maybe itll be best to just wait and see....

                    Comment


                    • #11
                      Re: La Pavoni undressed

                      Originally posted by Sparky link=1170566881/0#9 date=1173185227
                      Im not intimately familiar with relay failure, but audible humming from the switching coil doesnt sound right.... maybe itll be best to just wait and see....
                      Many of the high current relays (contactors) are operated on AC rather than DC...... and loose laminations (or even the coil being loose on the former) can cause that hum...... fingers crossed

                      Comment


                      • #12
                        Re: La Pavoni undressed


                        Fingers crossed indeed. Thats a pretty expensive part (although I do have a spare kicking around).

                        Comment


                        • #13
                          Re: La Pavoni undressed

                          Originally posted by Sparky link=1170566881/0#9 date=1173185227
                          Otherwise zi noticed the large relay that switches on the element seems to be humming. Im not intimately familiar with relay failure, but audible humming from the switching coil doesnt sound right.... maybe itll be best to just wait and see....
                          Another culprit with AC armatures is contamination on the main faces where the armature poles make contact..... quite a common problem and easily dealt with by cleaning with a suitable solvent and thoroughly drying out. This is the most common mode of failure for burning out the relay/contactor coil, as the less than optimum mating of the pole faces increases the reluctance in the magnetic path causing current flow in the coil to increase. Over time this leads to over-heating and accelerated degradation of the coil winding insulation and ultimately failure.

                          Always plenty of ways to skin a cat with these things

                          Mal.

                          Comment


                          • #14
                            Re: La Pavoni undressed

                            Thanks for those tips on the relay. Ill have a look and see what I can do.

                            Good news on the pump front. The pump I was originally using seems to be ok. I had a chat with a coffee tek this morning and he pronounced the pump good, but diagnosed the real culprit...

                            Whether by design or later modification, there is a check valve missing from the brew path, which means that hot water flows back into the pump and even further into the reservoir... The odd thing is that the machine didnt show any signs of being modified, so how this happened, Im not sure. But as soon as we got to chatting it all made sense, the pump and motor body getting too hot to touch and the reservoir water getting quite warm. I even noticed a couple of steam burps back into the reservoir...

                            I have a couple of check valves kicking around, so this will be sorted out asap.

                            Id like to have this thing up and running by the weekend... fingers crossed.

                            Cheers,

                            Mark.

                            Comment


                            • #15
                              Re: La Pavoni undressed

                              Mark...

                              Just a guess on my part..... but if using a reservoir then there is no positive pressure ..... whereas if connected to mains you would have 3.5 - 5.5 Bar pressure on the supply side of the pump....

                              Which would prevent and water flowing back from the brew path.... as it would have to overcome that pressure... For example - I always have 5 Bar in the heat exchanger which is a good idea so that the water doesnt boil- and deposit scale!!)

                              The machine was probably designed only to be plumbed in (hence no sign of a mod).

                              Comment

                              Working...
                              X