Problem with Nuova Simonelli Oscar...

by **johnny4lsu** on Thu Jan 17, 2013 6:59 pm

Here are the videos of the problems....Please help!!!!

https://www.dropbox.com/s/pqa8m6i4uicna....52.01.mp4

https://www.dropbox.com/s/m5qcyckb5hm5x....38.49.mp4

I changed the probe and it didn't help. Wondering if it maybe was the two way autofill solenoid valve. So frustrating.

Any suggestions?

by HB on Thu Jan 17, 2013 7:40 pm

To save members the motion sickness your videos are sure to induce, I captured a key frame below:

You moved the camera so quickly, I lost track of which way was up. Anyway, judging from the photo, it looks like the steam boiler pressure release valve, which could mean the boiler water level sensor is failing, leading to the boiler being filled to the top. If you post a photo of the leaking valve, it would be easier to confirm.

by **johnny4lsu** on Thu Jan 17, 2013 7:50 pm

sorry for the bad video. Ill take pictures when i get home.

by **johnny4lsu** on Thu Jan 17, 2013 9:08 pm

https://www.dropbox.com/s/081hntklj1gcj....20.15.mp4

Here is a better video.

by HB on Thu Jan 17, 2013 9:34 pm

For future reference, a still photo is better than dropbox and a video (see Posting images on HB for instructions). Here's another photo from your video:

It confirms my original suspicion: The steam boiler is full to the top with water; it's supposed to have a cushion of steam (see Heat Exchanger in Espresso Machines 101 for details). Judging from the crusty external appearance of the boiler, my guess is that the water level sensor is caked with scale. The scale acts as an insulator, preventing it from detecting the water level. You could try draining the boiler and cleaning the water level sensor, but I'd bet the steam boiler is choking with scale and in desperate need of professional servicing.

To be clear, the safety valve is opening because it's designed to open at steam pressure (around 1.6 bar), but it's being pushed open by pump-driven water (around 9 bar).

by **johnny4lsu** on Thu Jan 17, 2013 9:50 pm

Is the water level sensor inside the boiler?

I can drain the boiler, but how do I get to the sensor?

Can I just pull the autofill probe out and put descal inside the full boiler and let it soak?

Sorry for the rookie questions.

by **johnny4lsu** on Fri Jan 18, 2013 12:58 am

Descaled the Oscar. It actually wasn't scaled up that bad. It appears to be working fine now. I think the main problem was the boiler being full to the top. (not sure how it happened)

Anyway, thanks for the time and help.

by **johnny4lsu** on Sat Jan 19, 2013 10:30 pm

Oscar worked fine today until this evening. Went to pull a shot and noticed the heat light wouldn't come on. I checked to see if the red safety button didn't trip on the boiler but it was normal. The heating element is fine.

So, I decided to take the Oscar apart to get to the brain. The pictures below are what I found. Apparently it has some water damage from looking at it. Could this be causing my problems?

If so, is this repairable or should I just get a new one? Any way to test this with a volt meter?

Here are the pics.

https://www.dropbox.com/s/gmt4gm2zq6tiq....22.12.jpg
https://www.dropbox.com/s/g5g19lpzcvdty....23.38.jpg
https://www.dropbox.com/s/30gppjqgsbyss....23.50.jpg
https://www.dropbox.com/s/oss14nkg36pmp....24.29.jpg
https://www.dropbox.com/s/z6zepd5omr7sv....25.02.jpg
https://www.dropbox.com/s/6ha8nk6bdl46o....25.25.jpg

by **caeffe** on Sun Jan 20, 2013 2:07 am

That doesn't look good

As far as testing with a volt-meter - i couldn't tell you.
However, if you do decide to replace (or repair) the GICAR I'd suggest you figure out how it got water in there. You'll need to understand that before you replace the box so you can prevent it from happening to the replaced/repaired box.

by **allon** on Sun Jan 20, 2013 2:34 am

Looks like minerals from water may be borking it up.
If nothing got zorched, cleaning it up may do the trick. Brush gently and use deionized water. You can dry it with a little help from isopropyl alcohol. If that doesn't do the trick some rework may be in order, if those chips aren't custom they may be worth just replacing (not too difficult for someone with a little SMT experience but daunting for someone who has never messed with a soldering iron, I'm sure).

Good luck.
Edit: the chip is http://www.ti.com/product/uln2004a

Digi key has em for < $1


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