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1976 La San Marco Tipo 75 two group

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  • IamOiman
    replied
    I fixed the valve leaks from a suggestion made by a contact. The main nut that secures the toggle to the valve body is not supposed to be fully tightened. Doing so pulls the toggle body into the valve stem and keeps the valves permanently open. It does not need much turning to adjust the valve where the gasket seals against its lip, I only needed one half of a turn for both valves.
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    After some on/off cycles and chasing most of the leaks away I was able to pull my first shots this morning. The new springs are quite strong so I did not coarsen my grind size and used 15.5g of Saka Espresso Bar to good effect.
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    Unfortunately I'll need to stop and think what to do for addressing the one persistent leak (and one I expected): the hot water pipe fitting. After multiple attempts and applying more and more loctite 55 the worn threads on the fitting do not lock well to the boiler fitting threads, and a leak always develops. It is not like the modern San Marco machines that use a 3/8-1/4 BSP fitting as far as I know and uses a currently unknown thread size that is not BSP. I will need to investigate and see if a new fitting is necessary.
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  • IamOiman
    replied
    I did turn on the machine tonight, wired for 240V 20A (the original elements are calculated to draw 13A). I filled the boiler with 7 liters of water to immerse the elements fully. I let the machine start pressurizing briefly and noted three leaks: one of the steam valves and the hot water valve leak from their valve gasket even though the actuating arms are in their rest position. I am unsure if that is due to weakened springs or poor seating of the valve gasket. The third leak noted was the hot water pipe to the boiler connection but I will need to see what else will leak if I can get to operating pressure first. For tonight though I will let the machine cool down then tighten the fittings a little more.
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  • IamOiman
    replied
    To connect the pstat to the boiler I had to adapt one of the original nuts to a pipe I made. This is because the thread the nut screws on is not BSP, but a metric thread. I used a compression bushing instead of a normal nipple when brazing. I then used an adapter to go from 3/8" BSP to 1/4" BSP and had a second pipe brazed to connect to the pstat. I also made another pipe for the steam arm since the replacement fitting for the steam valve is not the original 3/8" BSP. Wiring was the last step completed before testing.
    Click image for larger version  Name:	new steam pipe brazed pipe.jpg Views:	0 Size:	151.1 ** ID:	932515 Click image for larger version  Name:	compression nipple vs sleeve.jpg Views:	0 Size:	209.9 ** ID:	932519 Click image for larger version  Name:	new pstat pipes with pstat.jpg Views:	0 Size:	186.1 ** ID:	932516 Click image for larger version  Name:	compression fitting nut.jpg Views:	0 Size:	180.8 ** ID:	932518 Click image for larger version  Name:	wired LSM 75.jpg Views:	0 Size:	204.4 ** ID:	932517

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  • IamOiman
    replied
    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.
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    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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  • IamOiman
    replied
    The cup warmer valve came together too. And this is the current state of the machine. I was waiting for 240V to be installed which happened today, so I can proceed forward with my two San Marco machines. The breaker is 20A 240V with GFCI, plently for my needs.
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  • IamOiman
    replied
    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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  • IamOiman
    replied
    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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  • IamOiman
    replied
    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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  • IamOiman
    replied
    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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  • IamOiman
    replied
    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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  • IamOiman
    replied
    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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  • IamOiman
    replied
    __________
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  • IamOiman
    replied
    Click image for larger version  Name:	pressed pin.jpg Views:	0 Size:	165.1 ** ID:	925427

    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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  • IamOiman
    replied
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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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  • IamOiman
    replied
    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.

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    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.
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    Last edited by IamOiman; 20 August 2022, 11:57 AM.

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