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  • #16
    Re: Classic Pressure?

    Welcome to CS Jimbo. Im glad youre finally learning how to make decent coffee on the Classic. My Classic has still set the high water mark for espresso for me, even though I have since moved on. However, to get the best out of it you really do need freshly roasted beans and a good grinder. But you seem to know that already.

    The pressure mod makes the greatest difference if you are making single basket shots or double basket shots with restricted flow (double ristretto). The difference is most noticeable in the thickness and quality of the crema. This also enhances the flavour of the shots. For this machine, the mod is so easy that its worth trying it to see for yourself. After I made the change, my ristretto shots came out like thickened cream and the crema lasted for a long time. The mouthfeel of these shots is smooth, thick and velvety. If you experience these qualities in your shots you wont want to go back.

    The water starts exiting the OPV as soon as you start the pump, so both methods of timing are identical.

    Regards,

    Mark.

    Comment


    • #17
      Re: Classic Pressure?

      Thanks for the welcome Mark.

      I tried the mod earlier today.

      I must be doing something wrong bacause I get different amounts of water in my measuring cup depending on how long I leave the machine on between runs.

      Is there a specific method? ie waiting a few minutes then turning the pump on.

      Do you make the adjustment then wait several minutes for the machine to heat up before turning the pump on?

      Sorry for all the questions.

      Cheers

      Jim

      Comment


      • #18
        Re: Classic Pressure?

        No worries with the questions. The OPV doesnt require the machine to be hot. It should work straight away. Adjust the OPV (I found 270 degrees counter-clockwise about right) and then close her up. Youll need a to do one of the following to check if it is correct. Either use a blind filter basket in the portafilter and lock it in (you use this for backflushing, to stop water exiting the group) and then press the brew switch. The other alternative is to turn on both the steam switch and the brew switch (the method used to get hot water through the steam wand), but keep the steam valve closed. This should turn on the pump but keep your 3-way valve closed and let water exit the OPV return pipe. One note here is the 3-way valve itself can act as an emergency relief valve and will usually open at some pressure above optimal brewing pressure, such as 10-12 bar. If this happens, youll see water coming out of the group as well. It can also be a good indicator that youve lowered the OPV setting enough when this flow through the group stops (if it occurs at all).

        I used the blind filter basket method, so didnt have to worry about the 3-way relief pressure.

        Hopefully, youll be able to figure it out from here.

        Cheers,

        Mark.

        Comment


        • #19
          Re: Classic Pressure?

          Mark,

          Youre right about the Carezza - I was just thinking Gaggia - but the Carezza doesnt have a 3 way, and I dont know if its got a OPV - although it does have the tube from the boiler back to the water tank, so Ill check and see when I get a moment.

          Will update this if it does. Otherwise- I just knocked out another shot, and it sure did seem thick and smooth... so perhaps ignorance will be bliss?

          Comment


          • #20
            Re: Classic Pressure?

            Hi again,
            I got around to doing the OPV mod on my Classic over the weekend and, like the others, Im very happy to have done it.
            It was relatively quick and painless thanks to all the detailed info in this thread.
            Kudos to Mark and Ben especially.
            I ended up settling for 125ml per 30 seconds flow from the return line against a blind filter.

            In my case - it was very lucky that I stumbled onto this thread and felt the need to open up my machine. I found, to my horror that, the U-shaped metal bracket that holds the pump was heavily corroded!
            This is the bit that keeps the pump upright and lifted - so the inlet pipe can snake up under it and into the pump inlet. The pup itself is attached to a metal plate that attaches to the bracket via 2 screws.

            Youll understand why in a minute.
            The intial flow from the return line was less than 50ml in 30 seconds from the stock machine. The pressure buildup in the system was enough that there was leakage at the point the inlet pipe went into the pup as the OPV just couldnt pass enough water.

            Ive cleaned away as much rust as I could and Ill just have to monitor it now and hope that it doesnt get any worse - now that the OPV is doing its job. <touch wood>
            Thankfully - the plate the pump is attached to, the pump itself and the boiler and surrounds are all pristeen. The rust is confined to the bracket and some staining around it.
            I have to keep an eye out that no rust flakes off and finds it way into my water tank now - the shelf that the bracket attaches to doesnt seal off the water tank area.

            Another shock was that the inlet pipe was showing signs of serious wear due to rubbing against the metal bracket. In one place it was nearly rubbed through. Ive taped it up for now but will see if I can find a replacement somewhere.

            Jim - the way I did my measurements after making adjustments was to run the pump against the blind filter until water started to run from the return pipe. I then stopped the pump and got out the measuring cup. Id restart the pump and measure the flow in 30 seconds.

            I did this as I found the volume of water remaining in the return pipe would be different every time I took it and the attched nut off the OPV to make adjustments. This ensured that the volume out of the return pipe started at a consistent mark.

            I didnt do anything special temperature-wise. I just turned it on after pulling it apart and started doing the testing. I think that prefilling the return pipe prior to doing a test will solve the inconsistency problem.

            Hope this helps

            Frankie

            Comment


            • #21
              Re: Classic Pressure?

              Hi Frankie,

              Im glad you got it sorted. The extra steps you mention I just took for granted. Thanks for the addition.

              Its an excellent mod at no cost with great results.

              Cheers,

              Mark.

              Comment


              • #22
                Re: Classic Pressure?

                Could someone who has a clue please tell me if this mod can be done on a Gaggia Espresso (parts diagram is hopefully attached)? If so, which valve/nut is it?
                Thanks!

                Comment


                • #23
                  Re: Classic Pressure?

                  Hi BSOD,
                  looking at the partsguru site (I assume thats where you got the schematic from) there is a photo above the plan. The photo looks a lot like the one further up in this thread, where the return line to the tank comes off the top of the boiler where the steam pipe is instead of on the way into the boiler like the Classic. (around part 26)

                  If so - the non-adjustable nature that Sparky mentioned may apply.

                  That said - Greg hasnt chimed in yet to say definitively whether the OPV is adjustable or not in this configuration.

                  Might be worth the 10 minutes or so itd take to pull it open and have a look.

                  Frankie

                  Comment


                  • #24
                    Re: Classic Pressure?


                    I just bought one of these machines today, courtesy of Jack at Barazi. I had a look in the shop and it didnt look like there is any way to adjust the OPV in this machine. I only bought this machine for parts, so its not an issue for me.

                    Im still not 100% certain as I havent pulled it apart yet, but it doesnt look too promising.

                    Cheers,

                    Mark.

                    Comment


                    • #25
                      Re: Classic Pressure?

                      Thanks for the reply gz20tt. Yes, the schematic was from Partsguru. Just so I know exactly what I am looking for, could you please let me know the number of the part (or its approximat location) on the Classic schematic at http://www.partsguru.com/GaggiaClassicCoffee.html ?

                      Thanks!

                      Comment


                      • #26
                        Re: Classic Pressure?

                        Hi!
                        Is this the right place for doing the adjustment? The picture is showing my Gaggia Coffee Classic.

                        Mats

                        Comment


                        • #27
                          Re: Classic Pressure?

                          BSOD,

                          I just pulled my machine apart this morning and found what looks like an adjustable OPV. Its going to be hard to adjust, but it looks very adjustable. Its part 43 on the parts diagram. Its the very first t-piece that is attached to the output of the pump. One side goes off to the boiler and the other other side points down directly into the water reservoir. Very tricky and not easy to spot unless you pull the pump out. That said, in the end of that t-piece there is a screw with a hole in it. It takes a standard blade screwdriver and definitely adjusts a spring preload. In the one from my machine, it was set at some value (ie not max in or out, so factory setting). Id say this is the adjustable OPV. Now you just have to figure out how to adjust it.

                          I hope that helps.

                          Cheers,

                          Mark.

                          Comment


                          • #28
                            Re: Classic Pressure?

                            Dilbert3000,

                            Yep blue marks the spot. You just ahve to unscrew the top nut (with the black pipe coming off it) to reveal the adjustment inside.

                            Cheers,

                            Mark.

                            Comment


                            • #29
                              Re: Classic Pressure?

                              Mark - Ive had a look at the Carezza, and its the same sounding thing as part 43 on the Espresso. Tee-piece with a blade screw adjustment on the underside of it.

                              Was wondering how youve adjusted yours, and if you have, how did you test it without the blind PF? The Carezza doesnt have a 3way valve, and doesnt have the same backflushing ability of the Classic??

                              Comment


                              • #30
                                Re: Classic Pressure?


                                Hi Andy,

                                I didnt test mine. I pulled it apart for parts. At $30 it was cheaper than buying a boiler, which was what I was trying to do. Ill be using the pump system to test an idea for an electronic OPV. Nevertheless, you could still use a blind filterbasket. You can release the pressure by opening the steam valve into a jug. The hard bit will be accessing the screw adjustment and then attaching a hose to divert the flow into a measuring cup. The other thing to note is that the pump type. My pump is an Ulka EK2 which is a 55W pump with a slightly higher flow rate. Youd be looking at aboutr 150 ml in 30 sec for this pump, as opposed to 120 ml in 30 sec for the E5 pump.

                                Thats about as much as I can add as I wont be testing this myself. I hope this helps.

                                Cheers,

                                Mark.

                                Comment

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