Conti Prestina Espresso Machine Restoration 101 (Completed and Indexed) - Page 72

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
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drgary
Team HB

#711: Post by drgary »

Removing the back of the boiler was instructive, and I'm glad I did that at this time as I found some of the bolts have started rusting and will replace them with marine grade hardened stainless steel (type 316). Getting that boiler off without a flood can be messy but I minimized that. I held a wide-mouthed canning jar under the group opening and tipped the machine into it several times to drain the water. This way when I unfastened the bolts there were no drips. And here's what I found:

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This is what the boiler looks like on the inside, browned and stained but still pretty clean. When I rubbed my finger against the stain above the water line it had no smell.

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Here's a close-up to show the nuts holding the taps in place. It's a shame these fasten from the inside so one has to remove the back of the boiler to service them.

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Another design feature that prevents tightening the taps from the outside is the length of the dipper tube, which extends beyond the circumference of the boiler. That's a shame. Otherwise one could turn it from the outside, checking to see that it's pointed downward by reaching in through the group port with the group removed.

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This close-up of the water tap shows the service I want to secure to a smooth, unthreaded port. I think I'll use food-safe Loctite thread sealer where the nut threads onto the tap and inside the smooth hole and where the gaskets push in, hoping this creates enough friction. If not I'll have to apply a larger amount of JB Weld to the outside, because the first application didn't hold.

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I also noticed the beginning of scale, even though I've been using mostly distilled water. This means I'll need to keep up with a descaling regimen.

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Scale tends to build up especially where there's heat, as you can see here at the heating element terminals inside the boiler.

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And here's a photo of significant rust that had already started developing in the bottom boiler bolts. These had been exposed to some early leaks during initial testing. This amount of rust formed despite their being coated in anti-seize compound. I'm now ordering marine grade stainless replacements for all of this hardware. I've revised the section much earlier about hardware selection to show the need for stainless.

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Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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drgary
Team HB

#712: Post by drgary »

Over the last two days I finished replacing the bolts with 316 marine grade hardened stainless steel. I also generously used Loctite 2042 to better secure the steam and water taps, including where they join the boiler plate. That's expensive Loctite but it doesn't smell bad and I had it on hand. So far, so good. If the taps loosen again I'll make a flat aluminum bracket that catches the female junction between the taps and steam wand/water spigot and holds them in place. It would have snug holes that align them with each other and there's no way with that sort of arrangement they can turn. This morning I was delighted to walk into my kitchen and pull a shot that revealed the coffee flavors in high definition again.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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drgary
Team HB

#713: Post by drgary »

The fittings connecting the Sirai PSTAT to the manometer knuckle started to leak again. I've got a H-B party at my house in a few weeks, so I decided to simplify things and reinstalled the old PSTAT pipe, eliminating the vacuum breaker. The vacuum breaker run-off line had clogged, so this would need servicing anyway if I reinstall it. I tested the machine with the old Sopac PSTAT in place and it worked without leaks. Then I ordered a Jaeger PSTAT from Chris Coffee service, installed it the other day and find I like it more than the large, bulky Sirai. The Jaeger keeps a narrow pressure range (deadband). It doesn't make loud clicks like the Sirai. It gives me plenty of pressure range of adjustment and is easy to get at with the drip tray and grate removed. I'll resell the lightly used Sirai to someone who needs it. If I reinstall the vacuum breaker I'll get a brass fitting so I won't be working with dissimilar metals, and one where the connections don't require me to fumble at sweating compression fittings.

Here's the Jaeger PSTAT I ordered, with a link to its listing at Chris Coffee Service, who sells it.

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As a note to myself, for the Sopac, the power cord attaches to terminal C and the right heating element to terminal 1. The equivalent connections for the Jaeger are power cord to terminal 1 and right heating element to terminal 2. These were determined by comparing the very similar circuit diagrams printed on each switch.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

IMAWriter

#714: Post by IMAWriter »

drgary wrote:The fittings connecting the Sirai PSTAT to the manometer knuckle started to leak again. I've got a H-B party at my house in a few weeks, so I decided to simplify things and reinstalled the old PSTAT pipe, eliminating the vacuum breaker. The vacuum breaker run-off line had clogged, so this would need servicing anyway if I reinstall it. I tested the machine with the old Sopac PSTAT in place and it worked without leaks. Then I ordered a Jaeger PSTAT from Chris Coffee service, installed it the other day and find I like it more than the large, bulky Sirai. The Jaeger keeps a narrow pressure range (deadband). It doesn't make loud clicks like the Sirai. It gives me plenty of pressure range of adjustment and is easy to get at with the drip tray and grate removed. I'll resell the lightly used Sirai to someone who needs it. If I reinstall the vacuum breaker I'll get a brass fitting so I won't be working with dissimilar metals, and one where the connections don't require me to fumble at sweating compression fittings.

Here's the Jaeger PSTAT I ordered, with a link to its listing at Chris Coffee Service, who sells it.
Great stuff, Gary.

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Rob
LMWDP #187
www.robertjason.com

Cafedenda

#715: Post by Cafedenda »

Thanks for updating us on your Conti adventure. Since CC doesn't want to divulge the connector size of this PSTAT, could you tell us what size is that connection and how narrow is the deadband. The CEME in my E61 HX is not working as it should. The band is way too narrow at less than 0.1 bar so the machine cycles on and off much faster than before. I think I'll buy the CEME if the Jaeger is also right around 0.1 bar. Thanks.

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drgary
Team HB

#716: Post by drgary »

Let me suggest you contact Chris Coffee for that information as I'm busy preparing several lever machines for an H-B gathering. All I know is that it screwed right in where the Sopac connects without other modification. Not even a Sirai gives 0.1 bar deadband. The Sirai is rated at 0.2 bar. If memory serves the Jaeger is 0.35. All I know is in practice it may be narrower than that as I don't see the needle in the pressure gauge vary much and the coffee is delicious.

I looked up the CEME PSTAT on the Orphan Espresso website and it is listed as 1/4" BSP and as a replacement for the SOPAC. So that is probably the thread size.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

Cafedenda

#717: Post by Cafedenda »

Thanks, Gary. It probably is 1/4" BSP also since there are not that many sizes and 1/4" is about right. I think my CEME is defective because it doesn't seem to work right. I'll remove it for inspection first though.