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1976 La San Marco Tipo 75 two group

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  • #31
    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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    • #32
      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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      • #33
        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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