Conti Prestina project - Page 4

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
User avatar
drgary
Team HB
Posts: 14347
Joined: 14 years ago

#31: Post by drgary »

Is it chrome or nickel? Too long ago but might have been a portafilter in pretty mild citric acid. Robert Pavlis would know this better than me.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

User avatar
cuppajoe (original poster)
Posts: 1643
Joined: 11 years ago

#32: Post by cuppajoe (original poster) »

Hi Gary, missed your reply. Not sure, my guess probably nickel.

Still collecting bits, but have made some progress in the meantime. Picked up a circle cutter that did a clean job of fabbing the boiler gasket out of 3mm PTFE. A bit thick, but had it on hand. Bolt holes were done with an auto gasket punch kit.

Figured out how to reconfigure the Pstat using the original parts. Reforming the tube was the only part mod necessary, which makes it easy to revert to stock. Got the wiring sorted as well. Picked up 3 vintage ceramic terminal blocks awhile back and they have come in handy.

David - LMWDP 448

My coffee wasn't strong enough to defend itself - Tom Waits

Advertisement
User avatar
drgary
Team HB
Posts: 14347
Joined: 14 years ago

#33: Post by drgary »

That's looking really good. If you add a fitting just before the PSTAT you could have a vacuum breaker, which is really nice to have for startup. I really like the circle cutter and have been looking for a good way to cut gaskets.

I noticed PTFE gaskets on the steam and water taps. Those taps have a tendency to turn as you open and close them. Not a great design. I used medium-strength threadlocker to keep them in place, and that may not work with PTFE. Another option is to use just a dab of JB Weld as suggested by the Conti tech who helped me restore my Prestina. (He's a member who sometimes posts here, aka walker30.) Doug Garrott would probably frown on it, but the point is to keep it minimal.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

User avatar
cuppajoe (original poster)
Posts: 1643
Joined: 11 years ago

#34: Post by cuppajoe (original poster) »

Another good example of two heads being better than one. I was making adding the vac valve way too complicated. Fabbing a simple 'U' out of copper tubing with a T at the end would have done the job. Cher said she bleeds false pressure anyway, but if she changes her mind it will be a simple matter to add the vac.

The valve standoffs are sealed on the other side of the boiler with 3mm PTFE washers and cranked down hard. Simple use of the valves should not loosen them. There are also two other potential loosening points on the valve assemblies. The adaptor from standoff to valve body will be sealed with copper washers and Loctite 577. The valve bodies with just 577, as they need to be oriented properly.

Thanks for the feedback
David - LMWDP 448

My coffee wasn't strong enough to defend itself - Tom Waits

User avatar
bill
Supporter ♡
Posts: 526
Joined: 18 years ago

#35: Post by bill »

Thanks for the circle cutter suggestion, David. I'm ordering one on EBay now to have when I get around to restoring my Prestina.
Bill
LMWDP #43

I wasn't born in Texas, but got here as fast as I could!

User avatar
cuppajoe (original poster)
Posts: 1643
Joined: 11 years ago

#36: Post by cuppajoe (original poster) »

Thanks Bill, glad to be of service. I would go with 2mm PTFE rather than the 3mm. The stuff is difficult to cut cleanly, takes many, many, passes with the cutter. I also found ebay the best place to buy PTFE as you can purchase smaller quantities than the industrial suppliers.
David - LMWDP 448

My coffee wasn't strong enough to defend itself - Tom Waits

User avatar
bill
Supporter ♡
Posts: 526
Joined: 18 years ago

#37: Post by bill »

cuppajoe wrote:I also found ebay the best place to buy PTFE as you can purchase smaller quantities than the industrial suppliers.
Good to know, thanks for the tip! I usually go to McMaster-Carr for stuff like that.
Bill
LMWDP #43

I wasn't born in Texas, but got here as fast as I could!

Advertisement
User avatar
cuppajoe (original poster)
Posts: 1643
Joined: 11 years ago

#38: Post by cuppajoe (original poster) »

A little more progress while trying to source Conti OEM parts. Finally heard from cafeparts and sent a new list. Hopefully they will hear from Italy in a couple weeks.

Unfortunately the original U-cup seal for the water fill valve is leaking. Found another source and ordered a possible replacement. if it works, can start testing general operation.
David - LMWDP 448

My coffee wasn't strong enough to defend itself - Tom Waits

User avatar
cuppajoe (original poster)
Posts: 1643
Joined: 11 years ago

#39: Post by cuppajoe (original poster) »

Thought I had it ready to test, but element kept tripping the GFI. Have a new element on order, as well as new water and steam tap knobs and seals and will hopefully pick them up on Tuesday.

In the meantime, found a source for the water fill valve U-cup seal - http://www.theoringstore.com. Fits well and so far no leaking. They have a huge inventory. Also got an O-ring for the top of the group that worked.
David - LMWDP 448

My coffee wasn't strong enough to defend itself - Tom Waits

User avatar
cuppajoe (original poster)
Posts: 1643
Joined: 11 years ago

#40: Post by cuppajoe (original poster) »

Finally got the element sorted. La Spaziale has an element that will substitute for the Conti which is unavailable. 1st line sells it and Nuova Ricambi could order it, who are a half hour from me and also had the Conti parts for the water and steam taps. In the photo below, the upper element is the original and the lower the LS. The fitting spacing is a bit wider on the LS but it will fit. The LS fittings are also 14mm and the Conti are 13mm, so some drilling out is required.

Unfortunately the element mounting holes are pocketed on both sides and so are the new element fittings. The original used flat seals and the new uses O-rings. To get a seal required 'getting creative' as the Italians say. I ended up using two O-rings on either side of a DIY fiber washer. So far it has passed the first pressure test.


Unfortunately the 4mm PTFE I used for the boiler gasket is not working out. It seeps or ghosts at just about all the mounting bolts. Will start a separate thread on that as it is not machine specific.

Important - If you order the La Spaziale element make sure to order the nuts as well While they are 14mm, the thread pitch is some oddball spec.
David - LMWDP 448

My coffee wasn't strong enough to defend itself - Tom Waits