Conti Prestina Espresso Machine Restoration 101 (Completed and Indexed) - Page 66

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
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drgary
Team HB

#651: Post by drgary »

I finally succeeded in hooking up the Sirai PSTAT and it does in fact have a much narrower deadband. Here's a photo of the pressure test:

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I really struggled to get here, soldering and resoldering the caps at the end of that short pipe. Then one of them broke and I had to shorten the pipe, turn it around, and put a sleeve on instead of a bicone cap. Then the sleeve would slip through the compression cap until I wrapped it in ptfe tape and it held firm. So now the pipe leading into the PSTAT has a Teflon wrapped sleeve and even a Teflon gasket to make the exit hole narrower. I hooked it up and the bicone cap that had been working fine attached to the Sirai leaked at the bottom of the T fitting. Ugh! Well, if pfte would work in one place, why not another? This was a fix I gleaned from the OE website, and it worked. Finally. I'm not a fan of compression fittings.

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My next step will be to secure the PSTAT in place using cable ties. Then I'm ready to secure the steam and water tap with a little Loctite 567 thread locker so they don't turn. I've received Melamine for boiler insulation and will cut that while wearing a breathing mask. Then I'll put the case back on and see if I can attach a quick release fitting to the water inlet.

I've finished filing the drip grate top plate to size and can now have that tack welded. Before I do that I want to eyeball it with the front plate installed and will add a chrome molding to the very back.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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drgary
Team HB

#652: Post by drgary »

Securing PSTAT, Taps and Wires

Now that the PSTAT is working, I started securing everything place before the final pressure test. To support the PSTAT independently from the pipe I followed Doug's suggestion to use a cable tie, a very large one. It's wrapped behind the pipe underneath the PSTAT, cradles the sides and connects with a smaller cable tie that's threaded through the hole securing the manometer bracket.

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Here you can also see the vacuum breaker runoff tube routed toward the drip tray. Although the PSTAT appears to be sticking out too far to the side I fitted the case to the back. The PSTAT fits easily and the case provides an extra support.

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The runoff tube is tied to the water inlet valve and terminates over the drip tray. I'm using some bare copper wire for this and latex tubing rated for 175 degrees F.

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I also stripped the ptfe tape from the steam and water tap threads, cleaned them with a wire brush and applied Loctite 567 to the threads. This should prevent them from turning.

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Otherwise I've used small cable ties for the wiring so it's now out of the way.

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Tomorrow morning I'll do a final pressure test after the Loctite has had a chance to set.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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drgary
Team HB

#653: Post by drgary »

Close Call This Morning

After thinking through all the details above and hurrying to tidy up before the Superbowl :cry: , I thought I had things ready to go. This morning I went out and turned on the machine, then went into the house for breakfast, knowing it takes awhile to heat up. The only problem is I forgot to close the water tap. (!) When I checked 1/2 hour later there was water on the garage floor, the sight glass was empty and the drip tray full of steaming water! I checked the element resistance and it's fine and steady. Whew! I couldn't turn the machine on, though. Fortunately the GFCI had tripped. The thermal fuse failed (stayed intact). So I've ordered a heat safety switch from Orphan Espresso, one where I can strap the bottom onto the front plate of the boiler to have double protection.

I learned and confirmed a few things from this. Of course, always check to make sure the taps are closed. With a machine that has a valve that turns open, it won't easily remind you of its status compared to an Elektra Microcasa a Leva where the switch looks open or closed. You've got to check it. When preparing a machine with a new setup, don't hurry. Don't test a machine without watching it closely. Do pressure testing in the garage in case there are leaks. Think about how much a custom heating element costs. Know that a thermal switch or fuse must be placed so it will easily overheat if necessary. Use a GFCI whenever possible.

Added: To put this in perspective, a fried element would not be a catastrophe, just expensive and time wasting. At this point I know the machine so well I would still have a fine machine near the end of restoration.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

cafebmw

#654: Post by cafebmw »

loctite 567 is only a thread sealer, it does NOT have any threadlocking properties! you can use threadlocker, which locks and seals, like loctite 243 (up to 360F) or, to be on the safe side, loctite 246 (up to 450F) resp. 2046 for food compliance. you still can disassemble it with tools only and no heat.

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drgary
Team HB

#655: Post by drgary »

Thanks, Oliver. I looked up its properties before using it and believe it has a moderate hold. This morning when I went to turn the taps they were held in place by the Loctite. If it fails to keep its grip I'll look into your option.

Here's where I got the idea to use that product:
erics wrote:Some side notes:

A threadlocker will also act, secondarily, as a thread sealer and a thread sealer will also act, in part, as a threadlocker. I believe you need to differentiate between "food handling" equipment and products that carry NSF approval for potable water use. One US manufacturer of espresso machines (which do have NSF approval) uses Loctite 262 threadlocker and Permatex 24240 threadlocker in their assembly depending upon the specific machine area. No teflon tape is used on any part.

edit - to directly answer one of your questions - Loctite 567 threadsealer will also act as a threadlocker.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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drgary
Team HB

#656: Post by drgary »

Follow-up on Close Call

I couldn't wait until morning so checked out the Prestina tonight. I checked the resistance at the heating element terminals. It was just as before and steady. I refilled the machine with the steam and water taps closed and then plugged the thermofuse back in and turned it on for a moment and the GFCI tripped. Then I substituted wire for the thermofuse. The GFCI tripped. I noticed that the area around the power switch was wet as was the grounding wire near it. I dried these. Turned it on and the GFCI was okay. Yay! Tomorrow I'll make sure that area is completely dry and will use a hair dryer to make sure. Then I'll wrap the power switch terminals with Rescue Tape to avoid any other shorts caused by water on contacts.

Also I tested whether the Loctite 567 is holding the steam and water taps in place. It is. Rock solid.

When I get a thermal safety switch from Doug and Barb I'll substitute that for the thermofuse. But the thermofuse may have stayed intact because the heating element didn't overheat. The flooding drip tray must have short circuited things before it had a chance to do that.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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drgary
Team HB

#657: Post by drgary »

cafebmw wrote:loctite 567 is only a thread sealer, it does NOT have any threadlocking properties! you can use threadlocker, which locks and seals, like loctite 243 (up to 360F) or, to be on the safe side, loctite 246 (up to 450F) resp. 2046 for food compliance. you still can disassemble it with tools only and no heat.
Oliver:

After testing today you're right! The tap turned. I'll get a true thread locker like you recommend. I hesitated to order Loctite 2046 because it's very expensive, over $38 shipped from the low cost source. But it's a 6 pack of 12 ml tubes so I'll sell off the rest in the Buy/Sell forum. Added: The listing is incorrect. That's the price, shipped, per tube, and is comparable with selling prices elsewhere. I've now got the stuff and will use it.

Also there is still a small leak at the bottom of the Sirai PSTAT. These compression fittings are really a hassle. Added: But with a dozen more turns of ptfe tape that fitting is sealed. I checked and the compression sleeve was holding in place where I soldered it. And now I'm ready to pull shots again.

Added again: 19 gm Harfusa Yirgacheffe, Pharos grinder. More layers of flavor. I think my latte art's going to improve fast. So that's how easy it is to get microfoam with commercial steaming! :D

And now another slow leak under the PSTAT. !!! Soooo close!

Fixed the leak. I'd wrapped the pipe and collar in ptfe tape and had inserted a home-made Teflon gasket in the compression nut. The Teflon gasket tore and was the source of the leak. Now the compression nut seals tightly against the many windings of ptfe tape. Whew!

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Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

jedovaty

#658: Post by jedovaty »

I'm not looking forward to tracking down leaks. Just hoping it won't be as bad as on an old diesel mercedes :roll:

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drgary
Team HB

#659: Post by drgary »

Hey Jano:

I'm finding every way to fumble through it so you can learn from my mis-steps. When you pressure test yours by all means close the water tap!!! :lol:

BTW this tube is a bit lively so I'm going to find an elbow fitting so it discharges down into the drip tray.

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Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

jedovaty

#660: Post by jedovaty »

The runoff tube is part of the p-stat?

I'm all too familiar with lively hoses. :oops: