I've scored NS Oscar for $30 and decided to modify it. Group head and PF were very dirty, gasket hard and cracked.
I had to break spot welds on shower screen to clean the mesh as it was totally blocked.
Spot welded it back after heavy scrubing and installed new gasket ($10).
Also installed o-ring between shower screen and dispersion disk.
Installation of restriction orifices as per Musica.
I had to use 3.3 mm for top inlet as temperature was slightly dropping during the shot with 3.2 mm.
Now it is stable within 0.5 deg C.
Pulsation damper
Gauge pressure was vibrating badly during the shot so decided to fabricate pulsation damper.
Membrane is from silicone kitchen dish and pumped on one side to 4.5 bar through tyre valve.
Temperature probe
It is K-type and made from compensation wire.
First I've installed it at the inlet to Neplas but readings were not reflecting shot temperatures.
Relocated it to the group head at small distance from dispersion disk.
Pressure transducer
Old pressure switch had 0.3 bar deadband so had to go.
Transducer voltage goes to LM311 voltage comparator and SSR. Reference voltage is adjustable through pot installed next to temperature display in front of the machine.
Range is 1.0 to 1.5 bar and deadband 0.05 bar.
Temperature display
Circuit is 4,5 digits but I had to downgrade it to 3.5 digits as 2-nd decimal digit was changing continuously by up to 5 units and it was distracting. Pot on right side is for pressure adjustment.
