Conti Prestina Espresso Machine Restoration 101 (Completed and Indexed) - Page 61

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

#601: Post by homeburrero »

drgary wrote:As I was leaving the garage I turned off the light. At that moment I heard the GFCI trip.
Might be worth doublechecking that you don't somehow have a switched neutral. With the garage switch off you should see no voltage between ground and either slot of the wall outlet.

Better yet, use an outlet tester -- all three lights should go out when the switch is off.
Pat
nínádiishʼnahgo gohwééh náshdlį́į́h

User avatar
drgary
Team HB

#602: Post by drgary »

Pat:

Is there a way to test that with a multimeter?
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

User avatar
homeburrero
Team HB

#603: Post by homeburrero »

If your multimeter has thin enough probes you can set it on the appropriate voltage range, then with the outlet's switch on put the black probe in the ground, then try the red probe in each slot, you should see 110V in the narrowest slot. If you see 110V in the wide one then your polarity is backwards at the outlet. Then switch it off and try again. If you still see 110v in either slot you are looking at a neutral-switched circuit.
Pat
nínádiishʼnahgo gohwééh náshdlį́į́h

User avatar
RayJohns

#604: Post by RayJohns »

BTW, here is the tape I use:

http://www.amazon.com/Scotch-23-Electri ... 000V4P58M/

By 3M, part #23. Splicing tape.

Ray

User avatar
TomC
Team HB

#605: Post by TomC »

If you encounter more problems with the fabrication of the drip tray or the costs keep piling up, you can just buy one that measures the same dimensions you listed earlier in the thread here. They only cost $37.

http://www.homebrewstuff.com/stainless- ... mount.html

They have multiple sizes. The back wall mount part could easily be removed.

User avatar
drgary
Team HB

#606: Post by drgary »

Thanks, Tom.

If you look closely at those they work well for a beer glass but aren't level enough for a demitasse cup.

My drip tray grate is coming together. It takes time to figure out how to best do it and where to get the materials, but I think I have it solved, and if I botch the first workpiece I have a second one that's identical.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

User avatar
TomC
Team HB

#607: Post by TomC »

A demitasse cup would have to have a narrower base than any two parallel slats for it to sit off level, which is physically impossible. But it sounds like your set either way.

User avatar
drgary
Team HB

#608: Post by drgary »

Much Progress Today

To follow up on past issues:

- Tested the circuit and did not have a switched neutral outlet. Thanks, Pat, for showing me how to check that.

- Replaced the gooey electrical tape with Rescue Tape.

- Installed a green pilot light on the right, tested pilot lights and they work to show when the machine is powered on (right green) and when the heating element is powered up (left red on).

- Fastened the pilot lights in place using Blu Tac and soft thread sealer. Used cable ties to tighten pilot lights too. Here's a photo:

Image

Here are cable ties on the other circuits. I've left the hot (black) lead to the PSTAT long because it will need more length to connect with the Sirai PSTAT I'll install within the next few days. I'm again considering using a terminal block in the back to make the wire runs neater but I may live with it as it is because it works.

Image

I sourced a miniature ice cube tray on eBay that fits well as a drip tray. This one's 1 inch deep. I could use something up to 1 3/4 inches but a drip tray is better than no drip tray.

Image

Then I began to prepare the case parts for installation. This began with final clean-up, starting with the brushed stainless steel parts I intend to use. I had covered the workbench with an old (and ugly) towel to prevent scratches. While the polishing and prep was going on I brought the Prestina up to temperature to tighten the boiler bolts back to 15 foot lbs. The bottom bolt had begun a slow drip again, so this heat cycling is essential.

Image

I should have looked at the backs of the panels first. There were some rust stains to deal with and buffing compound from long ago. I polished off the rust stains with a felt tip coated with Mother's Aluminum Polish. The I went over the smudges caused by handling these panels on the fronts again, and I was ready to attach them.

Image

I took a break for lunch, turned the machine off and tightened all bolts to spec. When I returned I laid out the case parts for assembly. Sequencing things this way would allow the machine to cool so I could attach the case comfortably.

Image

When I first took out the sheet metal screws I was concerned I'd gotten the wrong size because they were too small to grip the case. Then I vaguely remembered that these were fastened together with sheet metal screws and what I'll call "spring nuts" for lack of vocabulary, but I wasn't quite sure which ones and where. Old high res photos were helpful as well as just puzzling it out. I got out the spring clips and coated each nut and each new screw with anti-seize compound to prevent rust. After the way this started, I HATE rust! I replaced the old sheet metal screws with slotted heads with Phillips head screws because I also HATE stripped screws and fumbling to get a screwdriver to fit the slot. The old screws had also rusted a bit.

Image

Here's how these work. When tightened the spring nut tensions against the frame for a very nice fit.

Image

Now I began to attach the case panels, starting with a side and back panel. I checked an old photo to make sure the orientation was correct.

Image

I was easily able to attach the two side panels and the Conti badge to the back. Now I had the back and sides together. But it's good I had some time. Because I don't have an installation manual, I redid several steps while figuring out how to assemble things and in what order. I began by taking off the group to position the front panel but found that with that panel attached, I couldn't attach the group. So I removed the panel, reattached the group and removed the portafilter holder. One of the hex screws is hard to get to this way. I managed it with a long hex key but would have done better to remove it while the group was removed. Well, I was finding my way.

Next I tried to attach the back and side panel assembly using the large chrome screws in the front that connect with square nuts encased in clips. At first I got these backward until I realized I couldn't reach the bottom nuts to tighten down the screws. Here's one installed backward.

Image

Here's how they should go.

Image

This is because the spring nuts fasten into square holes in the case, like this. But at first I couldn't get them in. The newly powder coated case left a narrower opening, so I had to use pliers to compress the clips slightly to get them to fit.

Image

Image

So I fastened the back and side panel assembly to the front plate and fit the cup tray on top, only to realize I hadn't attached what I'll call sandwich nuts, which clip the frame edge from both sides. It turns out these must be very precisely aligned. I realized the best way is to fasten the cup tray onto the side and back panel assembly before attaching to the front panel. Anyway, it's good I had time. I'm writing this so the next poor bugger who reassembles a Prestina doesn't have these headaches. Here are two sandwich nuts in place. I had to move them around a bit to align them with the screw holes in the cup tray.

Image

Okay. NOW I was ready to attach the entire back case to the front, and it connects with just four large chrome screws through the front plate. And finally my Prestina could try on his new clothes!

Image

There have been some happy accidents with this restoration. One of those was my inability to create a mirror polish. I think this machine looks much nicer with a brush finish.

Image

Also I'm following Doug's suggestion to leave the group cover off to display the amazing engineering of the group. I'm really glad I did that. It makes this machine look well proportioned, not awkwardly boxy. Another fortunate accident is the color coordination between the frame panels and the brass parts in the group and the steam and water taps. The color is intended to match our granite counter. Also replacing the group cylinder with a new brushed aluminum one matches the brushed steel panels. The machine looks completely updated. I didn't think a Prestina could look good. I certainly didn't think a Prestina could look this good!

Image

Still more to do, but this is really close to done. Next steps will be:

- To complete the drip grate after the steel plate arrives early next week;

- Insulate the sides and back of the boiler; and

- Install the vacuum breaker and the Sirai PSTAT. The pipe and fittings should also arrive on Saturday or early next week. After seeing that the back case comes off in one piece by loosening four screws I'll position the Sirai horizontally as the manufacturer recommends. This will also require making a bracket assembly similar to that used long ago by Bill Jackson.

If I feel ambitious in the future I may create a custom brushed steel panel that fits behind the group. Getting a flat fit will require an elbow fitting to replace a steam pipe that protrudes about 2 to 2 1/2 inches outward from the front boiler plate, but that would give a finished look. I'm still holding onto the old case parts should anyone want to restore this machine to its original configuration in the future.

To think this project came from searching for a Cremina for $250! :lol:
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

User avatar
arcus
Supporter ♡

#609: Post by arcus »

Wow, what a nice reveal! She looks fantastic w/o the group cover; in fact, so nice that I'm on a mission to find one of these now.

User avatar
drgary
Team HB

#610: Post by drgary »

Thanks, Arcus. Good luck with your search.

Today I'm going to try and install the Sirai PSTAT as the Sopac has a wide deadband at this point in its lifecycle. I'll test that deadband with a steamwand manometer before changing it out. I've looked up PSTAT info online and here's what I'm gathering.

The Sirai is so outsized because it's a commercial unit and is capable of running a much larger heating element than in my machine. No matter. It will work for mine. Paul Pratt's site has a good discussion of PSTATs, and he says the Sirai is rated with a 0.2 bar deadband at first, but that deadband widens as the Teflon membrane stiffens over time. Others have mentioned changing out the membrane every two to three years. Paul recommends mounting the PSTAT low for longevity as a hot environment may stiffen the membrane sooner. There's a rebuild kit that is almost as much as the Sirai itself, but the PSTAT isn't very expensive, $58 if I remember correctly. The drawback with the Sirai is its huge size, but I've determined it will fit in my machine. As erics noted from the spec sheet the Sirai is best mounted horizontally to retard scaling of the membrane. If only I had an erector set! But I'll figure out something simple.

I also briefly considered switching out my Sopac with a Jaeger that appears almost identical and would simply screw on the existing pipe. Chris Coffee likes the quality of the Jaeger but I've been unable to find specs, including deadband.

In any case, I received my other plumbing parts and assuming they fit I'll attach the vacuum breaker, which will be a big plus from starting up the machine and bleeding off the air once or twice before it comes to temperature. I'll finish securing plumbing pieces in position with some Loctite 567 used sparingly. I'm still deciding whether to fit a steel panel over the front gap. If I do that I'll do something so the steam pipe protrudes less and can allow installation of a flat panel in that place.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!