I took apart the original pstat. Unfortunately this older style of sirai does not have available spares from the big parts sellers, but it is certainly a cool piece. It is designed just like modern Sirais but with the diffrent membrane. I will be using a modern Sirai 20A for now but I will see if in the future I can get a spare membrane kit made for the original.
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1976 La San Marco Tipo 75 two group
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The hot cup tray valve was taken apart after my metal guy showed me you can clamp a socket in the vise to exert the leverage needed. Nifty stuff. It's the same design in terms of seals used in modern San Marco machines.
The body panels were washed up. I will keep them original, but I did need to bend back one of the side brackets and panels that appears to have been struck by something in the past. I used my vise to get the worst of it out. I also got rid of the crud on the lower panels using green scotch brite to pretty good effect. The feet are still at my metal guy's place since they are getting media blasted.
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I got my frame back from my Metal guy. It was powdercoated a black with 80% gloss, really shiny and nice looking. I also had him clean up the lower stainless steel panels that slip on the bottom of the frame, the boiler lid, and the corroded feet. The o ring I am trying out fit extremelly well, and it is a perfect snug fit inside. I am really optimistic it will work with this boiler lid style. Please don't mind the Marte missing its body panels in the back, that is how I found it best to move it without assistance.
I assembled the two groups when I received my Eevad order containing the last parts needed to begin. I first started with the lower groups and installed the preinfusion valve + one way valve. The former is a little difficult to install due to the strong springs necessary to keep water from escaping from the boiler when pressurized. I had to push down while turning the threads to get them to engage. The one way valve was easy enough to install, and they tightened perfectly in the correct position.
Last edited by IamOiman; 20 August 2022, 11:57 AM.
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The upper group starts with the lever fork and rod assembly. I was able to reuse the original bearings after cleaning and regreasing them. The roller pins will stick to the bushing when the tacky grease is applied. There is a lever fork pin that is pressed through the bushing and pins. My ball bearings were made in the USSR, and this is not the first time I've seen that on espresso machines.
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The felt washer is stuffed in a recess in the upper group housing and the piston rod can be inserted then secured with the bearing bolts. The springs can be installed after, and I had to compress the big spring about 13mm to allow the spring nut to thread on. At this point the upper group is inserted without the piston into the lower group because the fat piston v gasket flares out too much to be inserted from above. Thus it needed to be screwed in below, and is why I decided to just buy the tool for future maintenance. I was able to hand tighten the pistons enough they are when the groups are standing upright for the short term.
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With that they are both assembled minus the portafilter gasket and showerscreen. The preinfusion lever had the roller pins replaced but they are otherwise in good shape. There is a tiny bit of play with the left group due to wear but it should not impede function. I did however need to use loctite instead of a rod pin for the same group because it screws tighter than the pin hole can align properly.
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This is about 2 months worth of updates going on here.
After the groups were assembled I focused on cleaning up the little feet. They were severely corroded, so the first thing I did was media blast them. I then used a folded piece of 240 grit sanding belt attached to a jacob's chuck adapted for my little omega grinder to get rid of as much pitting without compromosing the integrity of the foot. I hand sanded dry to 800 grit then up to 5000 mesh grit wet (320 600 800 1000 1500 2000 3000 5000 grits were used). I am posting the original condition of the feet again because I was quite happy with the results.
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I replaced the rubber feet that were all basically disintegrated with new ones I sourced from rubberfeet.us Large Round Rubber Feet - .500 H x 1.312 inches. It cost me $7 with shipping and removing the metal bushing allows me to fit the M6 thread that secures the foot to the frame perfectly. I made sure there was clearance so the hex head was not touching the surface the machine rests on.
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I mounted the groups afterwards. I used new stainless setup studs to replace the old ones since they were slightly damaged in the thread (pre removal). I needed to make sure the one way valve was not interfering with the flange, which will happen if not tightened to a correct orientation. I did receive the piston tool so the pistons are tightened properly. When pulling the levers down they are so strong that the frame tilts without the boiler. However I hear rubbing of the spring and bore on the left group so I'll need to adjust that later.
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The bakelite handles were cleaned up and polished. They were lightly sanded then polished on my Baldor buffer with white tripoli. I learned a trick to use a screwdriver to hold the round piece against the wheel so one spot is not focused on during polishing (also useful for sanding which I did with the feet).
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The valves were assembled this week. The steam taps and hot water tap are the same design, but I had to replace one of the fittings due to cracks in the old one. The replacement has a 1/4" BSP thread so I will need to braze a new pipe for that. I also assembled the water inlet valve, but I will need to test if it can hold pressure since the modern inlets have a slightly different design. I am using a steam tap teflon conical gasket (which is what the modern ones use) and a 7x3mm o ring.
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The boiler was mounted with teflon tape and copper crush washers. I'll soon find out if I tightened the big two nuts enough connecting the boiler to the group flanges.
The heating elements were attached after to the cleaned boiler lid. The terminals and screws were also cleaned but separately in the tumbler. New M10 bolts were installed once the pstat bracket was made.
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