I have recently bought an ACS Minima, sold as being defective, at about the same time I was generously given a faulty Lelit Bianca flow valve kit by @thusband through this forum. I hesitate to use the term restoration on such a young machine but people may be interested in my experiences in trying to sort out the devices.
I have other machines including an ACS Evo Leva but wanted something to play with, I have had lots of other machines before but as I have never had a dual boiler E61 machine before, the Minima and flow control device fit the bill.
The Minima is an early one, number 51 dated March 2019. The seller told me that the steam boiler used to occasionally overfill and the fill solenoid had been replaced with one sent by Bella Barista. He said that it still overfilled after fitting the new solenoid, hence it being sold as defective, but it has not happened recently and may have cured itself. I have had the machine running for a few hours every day for about two weeks now and the boiler hasn’t overfilled yet. I’ll post my experiences with the flow control device later.
The first problem encountered was with the reseviour level switch. As it is an early machine the water container sits on a platform. The weight of the water depresses the platform and operates a micro switch under it. In this case the platform had settled on the switch leaving it permanently on so low water was not being detected. Easily fixed by bending the platform back to get proper operation.
Second problem is that the chrome plating on the mushroom had disappeared. There was a silver coloured sludge on the bottom of the mushroom and silver flakes on the gauze filter over the gicleur. I spent some time flushing the system out and still get silver coloured flakes in the drip tray water.
I don’t know why the chrome had come off, possibly over enthusiastic descaling? There was no sign of scale on the mushroom or anywhere else.
I replaced the three hole steam tip with a two hole version provided with the machine
The steam boiler temp was about 105C when I first got the machine, I set it to 128C and one day noticed that it was back to 105C. It has not happened again and i’ll keep an eye on it.
The machine now seems to be working perfectly, I make one coffee a day with it so not much opportunity to experiment to find the optimum settings. The first few coffees were disappointing, weak and under extracted. I noticed that the coffee was being extracted at 6 bar. I changed the basket to a VST basket, adjusted the grinder to grind finer, weighed in 18g of grounds and the coffee is much better. I am playing with a different Gene 101 roaster (I am testing it as it was also bought as being defective) at the moment so roasts are variable from one 200g batch to the next as I play with settings, so not much opportunity to experiment to find optimum settings yet as I don’t want to waste a lot of coffee dialling in.