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La Pavoni Modello Professional

Postby Heckie on Tue Jun 08, 2010 12:55 am

Ok so I am new to this site. I have worked on mine and customer's Pavonis for many years but can't seem to figure this out! :roll: My machine, La Pavoni Modello Professional Pre Millenium 1997 or 98
The issue.........
The 2nd and consecutive shots, coming out the portafilter spout are way too hot and therefore I get steaming hot froth-looking espresso (at that point it's not really espresso anymore) spraying out of the spout.
Normally, at home my machine is only used for the first pull, unless we have guests over or I happen to want a 2nd or 3rd. I was wondering for those that pull consecutive shots until the boiler is near empty, has anyone experienced the same condition? If I run the portafilter under cold water between pulls that seems to eliminate the problem. :D But weird thing is I have never had to do that with any other Pavoni I have used. Then again as I said I don't pull consecutive shots.
Boiler temp is set to .7 bar, which I had lowered a while ago, down from .9bar, to try to solve the issue. That didn't work .. Other things I have checked out:
All gaskets in entire machine are new and functioning properly, siphon tube is new, brass piston ok, no scale inside grouphead, etc.... All other possibilities have been exhausted with the exception of replacing pressurestat, which periodically malfunctions letting boiler pressure go to high but that is occurring independently of the main issue. So that's the deal any shared experience is welcomed! Thanks....
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Postby espressme on Tue Jun 08, 2010 11:41 am

You seem to know your machines and these are a couple of thoughts. LaPavonis do have a group temp problem but usually after the second shot.The chilled PF and/ or a cold wet towel are common fixes to the problem.
Since your machine has a pressure gauge, try shutting the switch off after the gauge says .8bar. Remember, the temperature of the boiler is for steaming and not really for pulls so the pressurestat is set to a higher temp than necessary for a pull.

The two switch LaPavs had a high and a low switch setting so one could keep the boiler idling at a lower temp than needed for steaming.

If the machine seems to still be too hot, the gauge may have been damaged and is reading too low.
A malfunctioning pressurestat is not a good thing!! If the little relief valve is scaled up it may cause a pressure problem as the excess pressure may not be able to escape quickly enough.

~Richard
richard penney LMWDP #090,
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Postby michaelbenis on Tue Jun 08, 2010 12:01 pm

Even when a Pavoni overheats the symptoms aren't as extreme as you describe and definitely not at the pressure readings you are seeing on your gauge, so given that you are sure the gaskets are OK it does sound as if you may have a problem with your pressurestat and pressure gauge, the accuracy of the gauge maybe having been affected by the pressurestat letting things rise very high at some point.

During preinfusion, with the lever raised, do you find that the beads of coffee drip from the portafilter quite quickly and regularly before you commence the pull, even with a fine grind? This could confirm that the boiler pressure is on the high side, especially for what is shown on your gauge.

Cheers

Mike
LMWDP No. 237
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Postby F.M. on Tue Jun 08, 2010 2:54 pm

Heckie wrote: If I run the portafilter under cold water between pulls that seems to eliminate the problem. :D But weird thing is I have never had to do that with any other Pavoni I have used. Then again as I said I don't pull consecutive shots.


I think that's the rub right there.

Once a week my inlaws come over, and I end up pulling 3 doubles in a row on my millenium pro.
Originally I started washing the basket between hots just because I wanted a clean basket for every shot. But then I noticed that 2 seconds of cold water on the basket and portafilter, then wiping dry, nearly solves the over-heating issue. Turning the Pavoni off during during the actual pulling of the shot seems to help too.

If neither of those things resolves the issue, then yeah maybe a bad pressurestat?

I have my pressurestat set at about .85 bar. Having the best luck with the double basket, single pull. The second shots generally seem to be the best. I know there is always room for learning and improvement with coffee, but at this point I don't think equipment is the path to higher quality. I like what I am drinking now too much to care really!
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Postby Heckie on Tue Jun 08, 2010 6:31 pm

Thanks everybody for chiming in here, all really great info.
~Richard, thanks.. relief valve checks out ok, but bad temp gauge is possible, as I think the previous owner had tried to unscrew the small screws on the back of it... So who knows what might have happened. Also, the pressurestat definitely needs to be replaced b/c it has been overheating, although I haven't ever let it get past 1.2 bar.
~Mike, the espresso doesn't drip quickly, with the lever up, usually takes 10seconds or so.. just a guess, depending on the grind.
~FM, thanks for confirming what everybody else here seems to have experienced: Cooling porta-filter handle and turning off machine to cool grouphead a little before pulling shots .... sorta replicating the techniques of using the old 2 switch Pavoni's.. I will test these methods again tonight to confirm and post my results..Thanks everybody!!
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Postby Heckie on Wed Jun 09, 2010 12:36 pm

Problem= Pavoni Portafilter too hot, the 2nd and consecutive shots, coming out the portafilter spout are way too hot and therefore I get steaming hot froth-looking espresso (at that point it's not really espresso anymore) spraying out of the spout.
Solution= Cool portafilter between pulling shots either with a cold rag or quick cool rinse.
Thanks
Everyone for helping out, my Pavoni and I are back in business... :D
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