Well I dialed back the Sirai half a turn just to hopefully eliminate any concerns of danger from too much pressure. I measured the temperature with a very accurate instant digital thermometer last night and again this morning. Last night water was 202 (measuring flush water) and 190 a few minutes later. This morning I measured the flush through a portafilter at 190 and, a few minutes later, espresso immediately in the styrofoam cup at 170! The espresso still had thick crema but tasted a bit sour.

Without having a better way to measure temperature or pressure at the moment, I'm guessing that a descale is my next best step. BTW my beans were 6-days-old yesterday. I store beans in an airtight container, buy a pound at a time from Stumptown here in Portland, and use within a week max.

Thanks again for all of the great tips!

I used to try and measure water temp from the Oscar with a nice digital thermometer/ foam cup. I never got any useful, consistent data. Eventually I just trusted the flush routine and stopped worrying about it. Ok, maybe I never quite stopped actually worrying about it.

Any advice on descaling Oscar? Thanks!

Considering nothing is broken, you should dial the boiler pressure with some reading. This idea from Orphan is a nice one to set the boiler pressure with no fuss.

I'm restoring two NS Oscar and the first one is running. I found that the brew temp rises a lot (using a Scace device), almost 5-6C during the shot. So Oscar's problem is not a cold brew temp, even at 0.9 bar boiler pressure.

Simonelli is using two flow restrictors at Musica, 3.2mm at the top inlet and 3mm at the bottom, and 1.3 bar boiler pressure. I had to make the M8 thread inside the inlets at my old group (Oscar from year 2000). But I've done few tests with 2 x 4mm restrictors so far.

Márcio.

marcbsilverman wrote:Any advice on descaling Oscar?

Here you go.