I've got a quick question about my Oscar, which I recently bought used. When pulling a shot, I've noticed that the pump will run with a normal hum but if it seems like it senses it needs more power, you can hear it almost kick in harder and the flow suddenly gets a little stronger. Is this normal? I'm still getting used to this machine. Thanks!
I am not sure what you mean about needing more power, but the pump may change noise with the heater going on and off. I have a Gaggia with PID and when the PID is on alarm function there is some temperature oscillation, heater on/off oscillation, and corresponding pump noise oscillation. Pump varies as its about 50 watts are overwhelmed by the heaters need or 1000+ watts on the shared circuit.
Very normal for a vibe pump to have different sounds depending on the amount of resistance. The pump will be loudest when there is no resistance and quietest when the flow is blocked, when blocked the pump is trying to makes its maximum pressure. The OPV on the Oscar is more there to protect the pump and keep the pressure below 14 bars. I believe what you are hearing while pulling the shot is the pump getting quiet as it hits the dry puck, as the puck saturates the water begins to flow easier and the pump is getting louder. The smoothness of the flow can be adjusted with grind and dose (always with consistent and proper distribution and tamping) which allows you to change the flavor of the shots.
Okay, well that's good to hear. In the meantime, I'm getting a bit frustrated with my shots. They aren't BAD, but almost every time I pull a shot, I get a soggy puck. Decaf, regular, light roast, dark roast, choked powder, coarse gusher, you name it. I thought I'd get a dry puck every time with the Oscar since I moved up from the Saeco, but it's still a long way from where I feel it should be. I keep worrying there's something wrong with this used unit, but I don't really have a point of reference as this is still new to me.
I know how you feel, I had never pulled an espresso shot before I got my used machine. I have had good shots with wet pucks. I sometimes get dry ones but mostly they are damp on top I think because there are a few drips that come off after I turn the pump off. What is in the cup matters.... Check that you have enough head space before you pull a shot do the nickle test. (espresso my espresso site tells you in great detail how to do it) Since I don't use the spring in my naked filter sometimes my puck sticks to the the group head so I don't believe it is a pressure thing. Just look at youtube for video of pulls to hear an oscar pump sound. And don't worry about the pucks that much.
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My pucks are always towards the soggy side unless I let the PF sit in the group foe a min or so. A 3 way valve is releasing pressure which allows the PF to be taken out with out a spray of hot water spraying everywhere, it does not suck every last ounce of moisture from the spent puck. Daily back flushing and weekly chemical back flushing keeps the my 3way clean, if is gets dirty you will understand the difference from a soggy puck to a soupy mess of a puck. I do not find a chemical back flush does much for getting all the gunk and oils off the screen and needs to be removed once a week ( for me ) to keep things flowing well and staying tasty.
I have recently pulled ristretto shots where the stream starts out fine, then a few seconds later the shot gushes out, accompanied by a louder pump noise. After this happens, I see a depression in the spent puck, indicating channeling. I could also observe this behavior with the naked portafilter whereby I actually saw a thin stream of water being expelled at the pf edge when the gushing occured! So my theory is that it depends on the bean type, grind fineness and the uniformity of the grinds in the basket (e.g. how well you tamped).
I'm starting to definitely think it's my technique, because this morning I had much more uniform (albeit overextracted) shots. I had no channeling, but I think my grind was too fine. I'm really impressed with the Vario-W and I really am loving it so far. I have a naked PF on its way from Chris' Coffee so hopefully that will help me out. I think my issue might lie in dosing and tamping especially since my tamper has ragged edges on it from where the former owner used it as a hammer! (no joke!) Again, I have a new tamper on its way as well. Also, how much should I be dosing into the standard NS doubleshot basket? I'm doing 22.5g with varying results, but am I overdosing?
My puck always comes out with a little puddle on top, but knocks out intact. I guess that's decent?
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