samuellaw178 wrote:How did you get the number? It was my understanding boiler safety valve is generally around 1.8-2.5 bar.

You are correct. the safety valve is at 1.8 bar. I'm not sure how I got those two mixed up. Hmm, back to the flat tire with water scenario. Maybe I can salvage this boiler, despite my best efforts to the contrary.

There's another safety valve which is the OPV (overpressure valve) that oversees the brew circuit (~9 bar operation and max 15-16 bar as you cited).

The stock Oscar does not have an OPV. It has the neplax valve on the grouphead instead. I believe that one was originally a fixed pressure valve at something like 16 bar. People have been changing this to an adjustable valve that can be turned down to 9 bar to control brew pressure. The downside of this mod, as I understand it, is that you get a bunch of water going into your drip tray every time you pull a shot.

The more I think about it, the more it makes sense to put an OPV in and plug the port in the side of the grouphead.

The $200-250 boiler sounds like a reasonable price actually. I've always thought it would cost an arm and a leg.

I think if I ordered the part through a North American supplier it would be something silly like $400. On the Elektros site it is listed at 85 Euros, silly inexpensive for a replacement part. Actually, all their prices are very, very good.

I talked to maintenance at work and they have no bsp taps. I've found a local supplier that lists a parallel pipe tap 55 degree thread angle, bsp joint type right hand and they have a 1/8" - 28. Quite the mouth full, but seems to fit the bill. I'll have to check them out tomorrow. I have a hunch this will be a special order if I go that route.

For the cost and effort, it is looking more and more like a retap an plug of this port and the insert of an OPV is my best option. There is no going back if I go this route though.

been there , done that
tap
group head most likely salvageable
there are at best 4 full threads , refit a new neplex with thread locker or sealant
there are more threads on the neplex than in the group head Do NOT overtighten
the nexplex is a safety for the HX and the 3way , I would retain that
if you want to play with pump pressure , OPV on the cold side , or rheostat the pump

boiler copper easily reshaped , go slow , small steps
my original oscar has a re-tapped group and a re-silver brazed nut

the grub screws for the over temperature cut-off are shorter than the ones for the bottom metal plate , they look the same , don't mix them up

chat friday afternoon plindy on skype or pm for #

G'luck

plindy wrote:been there , done that
tap
group head most likely salvageable
there are at best 4 full threads , refit a new neplex with thread locker or sealant
there are more threads on the neplex than in the group head Do NOT overtighten

Looks like Amazon is my choice. My inner impatient self really wanted this tapped today, even though I don't have a part to put in there.

The first thing I noticed about the neplax was the extra threads. The last person just kept cranking until it was in flush.

the nexplex is a safety for the HX and the 3way , I would retain that
if you want to play with pump pressure , OPV on the cold side , or rheostat the pump

boiler copper easily reshaped , go slow , small steps
my original oscar has a re-tapped group and a re-silver brazed nut

Locked down tight. Short sharp shocks. Not budging.


I'd try heating the boiler around the heater coil to expand it and then try again, but not having worked with copper like this I don't know if that is a good idea.

Time to remove that last fitting. Short sharp taps. Oooh, look! its moving. Tap, tap, tap, oops.

I don't know how that nut/fitting held on. Tried removing the fitting from the nut and the threaded end of the fitting was completely corroded as well. I think that's as far as I can go on this boiler.



The lighter areas inside the circles are the only parts of this ring that were still bonded to the boiler. I'm not sure how it actually held on and did not leak profusely.

plindy wrote:...
my original oscar has a re-tapped group and a re-silver brazed nut
...
G'luck

Ha, you knew where this was going.

I feel a little like this guy:


The view doesn't seem so good, but I don't want to give up.

Looking more closely at the boiler, the copper under where the nut was brazed looks to be in good shape. It looks like it was the brazing that corroded. If I can straiten out the boiler and clean off the corroded brazing, there is something to work with.

I actually just spent the last hour watching brazing videos (slow night at work). Back when I last tried this stuff, it was just copper and brass rod, no fancy silver stuff. The pros make it look easy. I know we have a couple of maintenance guys that are very good welders.

I also spent a lot of time trying to find a 1/4 bspp nut (I think that's what I need) and think I've finally found a somewhat local source. Living in the great white north, I don't have nearly the selection of products and suppliers you folks in the US do. I need to contact them tomorrow to see if they actually have stock. I should be able to get my neplax from them as well.

silver braze to avoid lead
however should also avoid cadmium
not cheap
Radnor saftey-silv 56 rod
Radnor Stay-Silv white brazing flux

clean/de grease base material , you can't get it clean enough
coat with flux
gentle oxidizing flame as not to reintroduce oxygen / porosity
heat all , flux turns clear ; add rod , done

plindy wrote:silver braze to avoid lead
however should also avoid cadmium
not cheap
Radnor saftey-silv 56 rod
Radnor Stay-Silv white brazing flux
...

Not cheap indeed. The best I could find locally was 2oz for $50. That's half the cost of a new boiler.

Why the high silver vs something like a 15% silver rod? The 15% silver seems to be what is recommended by manufacturers for higher ductility applications (vibration?) for brazing brass to copper. The high silver stuff is not recommended unless brazing copper/brass to steel.

If I can use something like a Harris Stay Silv 15, which I can find locally for $10 a rod, the repair makes sense.

The largest benefit of repairing this boiler is that I can test out the rest of the machine without too much additional cost. I have no idea how long this heater coil will last. Since I can't extract it, once it goes, I have to replace both the coil and boiler, so to me, it is not worth putting that much money into repairing.

might think about putting this project to rest for a bit , till you find a cheap non-working Oscar ...

Now where's the fun in that?

Cheap anything relating to espresso does not come up very often in Canada. This is the first time in a long while I've even run across an Oscar. I know they pop up quite often in the US, but they are not so common here.

I'm actually having quite a bit of fun with this. I just don't want to get carried away with how much I spend to get it working.