Conti Prestina Espresso Machine Restoration 101 (Completed and Indexed) - Page 46

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

#451: Post by drgary »

As a learning exercise, given what I've got and Doug's basic layout, here are the fittings I think need to be in place. Imagine Doug's photo above with vacuum breaker on top of a T and pressure release valve jutting out the side. Instead, there's an extender at top of the manometer, a T sits above that. On top of the T is my existing pressure release valve. Extending out the side is my vacuum breaker with dish, with its 90 degree pipe connected to the side of the T. Here's a more complete version of fittings I believe I need with sizes (please check):

1. 1/4 BSPP compression nut for steam inlet port of PSTAT or 1/4 BSPP double female elbow with 1/4 BSPP compression nut
2. Will my 1/4 inch U.S. tube with compression caps suffice or do I need a metric size?
3. Solder and flux. I don't know what to buy. I have a propane torch to heat it.
4. Assembly at top of manometer knuckle, which measures 3/8 BSPP per Doug and measures 16 mm or 5/8 inch OD of the male thread, needs A) 3/8 BSPP male/male extender to clear steam pipe that is brazed on so a T fitting can't turn into the thread in the knuckle; B) above that a T fitting with 3/8 BSPP female bottom, 1/4 BSPP male at the side where vacuum breaker connects with tube that bends upward through dish, 3/8 BSPP female at top; C) my existing pressure release valve installs at top of the T vertically.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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drgary
Team HB

#452: Post by drgary »

The Rattly Window Approach

Following Doug's example of (compulsively) using the parts I have because I have them, I undid the Loctite on all of my pieces and did some puzzle fitting. If I put the T (or in this case the cube) on the bottom, I can attach everything. Forget the curve in the pipe. That's there just to show it fits the bottom of that stack. I'm only missing is cap nut for the PSTAT, plus solder and flux. Putting the T below preserves the manometer positioning bracket too. If I can do this with 3 or 4 fewer adaptors (with the appropriate connections sizes on a different T fitting) I'll be happy but if I can't quickly source them I may just Loctite this together to test my machine. I can create more elegant plumbing later.

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This is essentially Dave's solution, replacing the Teflon tube with pipe and replacing the many adaptors at the PSTAT port with a single cap nut.

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I took apart the pressure relief valve, and it's a simple ball bearing held in place by the enclosure. It would be fastened in with the dish facing up, of course.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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drgary
Team HB

#453: Post by drgary »

I just got some coaching from LVX on how to solder the end caps and am sourcing the cap nut today, I hope. More soon.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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RayJohns

#454: Post by RayJohns » replying to drgary »

Make sure everything is clean, use flux and put the heat away from the joint a little (so it draws the solder into the joint) as opposed to on the seam of the joint.

Get yourself a nice push button mapp gas torch with an igniter (if you don't already have one).

If you really wanna be trick, you can silver solder it ;-)

Ray

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drgary
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#455: Post by drgary »

Thanks, Ray.

I assume you're suggesting I heat the pipe above the cap so the solder runs into the joint, right?

Lucio (LVX) told me that if I heat both the cap and the pipe well I can add the flux and solder without applying a flame.

I went to the best plumbing supply shop in my area yesterday to source an Imperial fitting, and they don't have any. Neither does the local espresso servicing company. But the plumbing supply place was able to sell me solder and flux that are free of lead and antimony. They suggest putting my workpiece in a vise and tell me that my propane or mapp torches will both work as long as I don't overheat things with the mapp torch. I also bought a pipe cutter as suggested by Doug.

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I've got a parts order in with OE to see if they can help me reduce the number of adaptors but need to have Doug review my posts above before that's sent. Doug and Barb are probably flooded with Pharos and LIDO orders to fulfill before Christmas. Meanwhile to keep this project going erics was kind enough to ship me a compression cap, 6 mm pipe, caps and ferrules so I can construct a pipe from the manometer knuckle to the PSTAT. At that point I'll be able to assemble this machine, if need be, with the other fittings I have.

So, unable to complete plumbing today I took some time for roasting and then had some moments to measure the Synesso drip tray grate to start planning my replacement drip tray fabrication. I've also ordered 3/4 inch steel edging from eBay.

Here are some photos of the Synesso grate to give you a sense of the beautiful piece I've got to work with. It has a lip in the back and curves in the front to wrap around the front of their machine's frame.

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Overall their grate isn't as wide as the Prestina's, which measures 7 1/4" from the front plate to the front edge of the frame and 13 1/4" wide on the outside of a frame where the ledge is 7/16". The size of the drip tray underneath can be up to 9 1/2" by 6 1/2" or smaller than that and can be any tray that will catch water. That's smaller than the inner diameter of the front frame to make room for the water inlet valve.

The Synesso grate is 6 5/8" deep from the back of the lip to the outer curve in the front. The width of the strip of holes is 6 1/4". For fabrication I'll have to choose which curves to cut. It's a shame because the Prestina has an upturned back lip. The Synesso grate bends to beautifully seat into the front of the Prestina frame. There are a few obvious options. I will probably need to add 3/4" edging on both sides to create a uniform, lateral hole pattern.

1. I'm thinking of keeping the front curve and cutting the lip off the back or maybe adding a piece to extend the lip backwards. I also would not use the entire curve of the Synesso grate but would cut and finish it to curl over the front of the Prestina frame.

2. I could turn it back to front, cut off the back lip and use edging to extend that forward. In that configuration the I could use flat edging at the back or cut it where it rises at back, creating a soft back lip instead of an abrupt one. That configuration would leave the hole pattern more centered.

3. I could use the flat surface only and attach edging pieces to frame it on all sides. The edging that's on the way is 3/4" wide. I could frame the hole pattern centered between the edging, but this would partly cover the edges of some holes and may not look as good as an off-centered but complete hole pattern.

4. I don't know a way to cleanly flatten out the bends. That would give me more alternatives, but I don't think it's an option.

The Synesso grate is just short of 2' 2" wide, so there will be enough left over if anyone else needs to fabricate a Prestina grate. It's 2 mm stainless steel. From photos I'm guessing it's a bright finish but haven't peeled back the protective plastic. The edging I've ordered accommodates up to 4 mm thickness and is bright stainless steel.

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Here's a view from the back:

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And the hole configuration in front. From the end of the holes in back to the start of the curve of the back lip is 1/8". There's 3/4" from the holes to the start of the lift in front and 1 3/4" from front of the holes to outside of front curve. In total the depth of the grate cutting out all bends is 5 5/8". The depth cutting out only the back lip is 6 1/2". If I choose to cut out the front curve and keep the back lip the depth would be 5 7/8".

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This view shows flats that will be cut off after I create the front lip. They will give me extra material to work with, if needed. The flat closest to the holes is 5/8", 1", then 1 3/8".

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Another measurement that may come into play is the flat surface on each outer edge before the perforations begin. That dimension is 9/16".

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I'll clamp the piece onto wood and plan to cut it with a hacksaw, will file and grind off any burrs or unevenness and then fasten edging into it with a few dabs of JB Weld. I'll use a protractor to cut 45 degree angles on any edging abutments. The edging piece is 1 mm stainless steel and is 3/4" wide.

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The same supplier, Rigidized Metals Corporation, has two other trim options. All are quite affordable. The first is a T channel, where the narrow width is 1/2" and the widest 1 1/4".

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The other trim option could work for a lip in the back and looks like this. I've written to find out measurements.

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Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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RayJohns

#456: Post by RayJohns »

You might also wanna pickup some plumbers sandpaper (it's a red sandpaper, kinda like tape) and is used for scuffing up the fittings (although any sandpaper will work; just make sure to clean everything).

And get yourself some spare copper pipe fittings to test and practice on first. And yes, be careful with Mapp gas, as it's much hotter than propane and it's easy to melt stuff. The other day I went to make a ring out of a Russian coin and the Mapp gas melted the coin before I had time to blink - oops.

When sweating pipes together, I use sort of an on/off method with the flame. You definitely don't want to over heat the pipe and you don't need full flame constantly. I apply the flame and watch the surface of the metal - you can see it flush with heat and changed color very slightly. It's almost like an invisible wave that goes over the metal. At that point, take the flame away, then apply the solder and see if it melts. Apply more flame as required, until the solder is sucked into the joint.

As far as where to put the flame, you want to apply the majority of the heat in such a way so that the pipe is slightly hotter inside the joint, not at the edge of the joint. Let me draw a little picture real quick.

Okay, see below there - you want to heat where you want the solder to draw into and avoid the initial temptation to heat at the joint where the cap ends.

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So cut the pipe, remove any burrs from the edges, etc. Then sand the surface, then apply flux.

Then heat until the flux melts (you can also apply the flux while it's hot - either way usually works). Heat all around the pipe, not just in one place. Avoid boiling away the flux. Touch the solder to the joint once you heat it up and circle the solder around the joint, then put the flame back and forth until the solder draws into the joint/fitting.

Then let it cool completely without any movement.

If you end up with an ugly drip at the bottom, you can wait until it cools, then clip the drip off with diagonals and file it down (or you can apply just enough additional heat to the fitting to remelt the solder just slightly).

And usually less is more with the solder.

Practice is a good idea. Once you do it a few times on a test pipe, then you'll get the hang of it. Just remember, you are not welding, nor brazing here - solder melts at a far lower temperature; don't overdo the heat and you'll be fine. And remember, clean, clean, clean surfaces and the solder basically tracks wherever there is flux, so make sure you flux the inside of the areas before you put them together.

Ray

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drgary
Team HB

#457: Post by drgary »

That's a gem, Ray. If you put a headline on it like "A Primer on Soldering a Compression Fitting" people will search and find it. Thank you!
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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drgary
Team HB

#458: Post by drgary »

Still Some Missing Parts

Try as I might, I've been unable to source all the parts to get this machine plumbed in as planned. I got all the way to here today and waiting for parts to arrive. Here's the bottom assembly connected to the manometer knuckle, with the vacuum breaker and everything else well sealed and firmly installed.

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Next was attachment of the pressure relief valve.

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Then connection of the water inlet valve.

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I arrived home after mail delivery and found that the compression nut and cap had arrived. But due to a misunderstanding, I don't have the 6 mm copper tube to hook up the Sirai PSTAT.

So ... inspired by the meanderings of Congress, I'm forced to move to Plan B, which is to attach the old Sopac PSTAT and the old pipe that connects it to the manometer knuckle. Except when I do this I'll have to temporarily omit the vacuum breaker because the old pipe connects directly to the bottom of the manometer knuckle.

If the old PSTAT works I'll be able to wire and test this Prestina over Christmas. However, I don't know how to disassemble and rebuild the Sopac PSTAT if it's scaled beyond functioning. I just have to hope that it works. And I'm not sure how to wire this thing. Fortunately the Sopac PSTAT is labeled with diagrams that explain to the electrically literate what goes where. Here are views of all of that labeling.

This first image shows the circuit of the switch and the functions of each of the three tabs, except I don't know what it means. It's the Rosetta Stone for understanding how to wire this thing. I think that when the hot lead, 1, contacts C, the circuit is closed and the heating element works. But I'm not sure. Maybe someone can verify or correct me here.

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Next I'll inspect the teardown photos and see if they tell me how to wire it.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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drgary
Team HB

#459: Post by drgary »

Wiring

Fortunately the teardown photos reveal where what wires were attached. Here's how the power cord connects to the PSTAT, the blue wire connects to the left heating element and the yellow and green wire grounds to the frame.

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Here's how the Sopac PSTAT was wired. The white wire connects with Terminal 1 and goes from there to the right heating element.

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The black wire from the power cord went to terminal C. Terminal 2 was vacant.

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Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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RayJohns

#460: Post by RayJohns »

In your wiring diagram, C should be the common wire. Not 100% sure what their diagram is trying to indicate, but there are only two possibilities here.

1. The diagram is saying that has temperature increases, the common is shorted to terminal 1

or

2. The diagram is showing the normal state and suggesting that as temperature increases, the switch moves up to short terminal 2

The easiest way to find out is to check the continuity of the switch while there is no pressure applied to it. You can either use a volt meter or a 9 volt battery and a little light or something. Check to see if current flows through C and 1 or C and 2.

If it shorts across C and 1, then that should mean that under cut off pressure, C and 2 are shorted.

Depends on what the rest of the wiring diagram for the machine looks like. Since it's just a P-stat that kills power to the heating element (right?) I would think you'd only need a switch that breaks the circuit, not something that opened one circuit and closed another (but again it depends on what all the machine is doing during its cycle).

Ray