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Fixing a laboratory waterbath

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    Re: Fixing a laboratory waterbath

    Sounds good I ll do that. I might use the lamp bulb trick here because I m worried about causing a short again. Like putting a 100w bulb between the primary of the transformer and the PCB.

    Comment


      Re: Fixing a laboratory waterbath

      Hey guys,

      I ll be posting some pictures of what I am doing to make sure I don't make any mistakes.

      First, the triac. I put thermal paste between the triac and mica and mica and heatsink. I put what I think is considered a thin layer. The triac is screwed to the heatsink with a washer so the screw doesn't touch the metal plate. I do not know the size of the screw but it is smaller than the triac hole. There is no continuity between the triac and heatsink or the screw and the triac metal plate. It all seems to be good but I d like to run it by you first.

      I soldered the new capacitor. The way I understand this is there is no polarity in film capacitors, and also it's AC so I don't have to watch for polarity. The transformer is back where it was. I believe everything is set. I m going to get a 100w bulb and hook it up between the transformer and the PCB.

      If you guys see anything abnormal please let me know. I m quite worried I either forgot something or did/hooked something wrong and do not want to have to go get new components once again.

      Thank you!
      Attached Files
      Last edited by vrasp; 07-19-2021, 12:02 PM.

      Comment


        Re: Fixing a laboratory waterbath

        the washer is a special one with a lip that goes into the triac so the screw cant touch the sides.

        Comment


          Re: Fixing a laboratory waterbath

          Originally posted by stj View Post
          the washer is a special one with a lip that goes into the triac so the screw cant touch the sides.
          Yes that's what I got. It came with the TRIAC.

          Comment


            Re: Fixing a laboratory waterbath

            One problem I see is that you are not getting your connection hot enough for the solder to flow and those connections are not going to be very good and you need a fuse holder ( or a fuse that has pig tail wire on the fuse ) and not solder the fuse to board like you did those are not going to be good connections

            I am sorry if it sounds like I am giving you a hard time with this but it is important that your soldering joint connections are solid so you will not have issues later on with this device

            When you see the strands of wire and very little solder on them this not going to be a very good connection you would be better off if used a piece of wire with the insulation still on the wire and go from point “A” to point “B” and make a good connection on point “A” to “B”

            Or

            You would have been better off if you had flatten the end of the wire across the the solder joint pads and solder it that way then your connection would have looked a lot better in the long run

            If you can find wire wrapping wire which is one solid wire and you laid them side by side and flowed solder on that to make solder trace you would have been better off doing that

            Are you using solder that has flux inside the solder if you are then the solder might not be of good quality if you are having issues with it to flow

            Not all solder that has flux in it are the same in quality be aware of this back in the day when Radio Shack was every where you could find good quality solder you can still find solder on there website however I do not know if the quality is still exactly the same as it was back then
            Last edited by sam_sam_sam; 07-19-2021, 01:16 PM.
            9 PC LCD Monitor
            6 LCD Flat Screen TV
            30 Desk Top Switching Power Supply
            10 Battery Charger Switching Power Supply for Power Tool
            6 18v Lithium Battery Power Boards for Tool Battery Packs
            1 XBox 360 Switching Power Supply and M Board
            25 Servo Drives 220/460 3 Phase
            6 De-soldering Station Switching Power Supply 1 Power Supply
            1 Dell Mother Board
            15 Computer Power Supply
            1 HP Printer Supply & Control Board * lighting finished it *


            These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

            1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
            2 Hem Saw Computer Stack Board

            All of these had CAPs POOF
            All of the mosfet that are taken out by bad caps

            Comment


              Re: Fixing a laboratory waterbath

              look closely at these places ...
              Attached Files

              Comment


                Re: Fixing a laboratory waterbath

                Originally posted by petehall347 View Post
                look closely at these places ...


                One problem I see is that you are not getting your connection hot enough for the solder to flow and those connections are not going to be very good and you need a fuse holder ( or a fuse that has pig tail wire on the fuse ) and not solder the fuse to board like you did those are not going to be good connections

                I am sorry if it sounds like I am giving you a hard time with this but it is important that your soldering joint connections are solid so you will not have issues later on with this device

                When you see the strands of wire and very little solder on them this not going to be a very good connection you would be better off if used a piece of wire with the insulation still on the wire and go from point “A” to point “B” and make a good connection on point “A” to “B”

                Or

                You would have been better off if you had flatten the end of the wire across the the solder joint pads and solder it that way then your connection would have looked a lot better in the long run

                If you can find wire wrapping wire which is one solid wire and you laid them side by side and flowed solder on that to make solder trace you would have been better off doing that

                Are you using solder that has flux inside the solder if you are then the solder might not be of good quality if you are having issues with it to flow

                Not all solder that has flux in it are the same in quality be aware of this back in the day when Radio Shack was every where you could find good quality solder you can still find solder on there website however I do not know if the quality is still exactly the same as it was back then
                This is good advice. I d rather you tell me that and I fix it rather then having to open everything back up to fix connections in a few weeks/months. This waterbath is supposed to run (if I m able to fix it for good) at temperatures from -20°C to 120°C. The connections must be good.

                I ve been under-estimating the power of flux. I will reflow solder on these connections with some flux see what I could do about that fuse.

                Thank you!
                Last edited by vrasp; 07-19-2021, 03:36 PM.

                Comment


                  Re: Fixing a laboratory waterbath

                  It's not the temperature range of the bath that's the problem, the phase change motor's vibration is what kills electronics. I'd suspecting it's what killed your connectors in the first place, and perhaps if that avenue was checked first, there wouldn't be so many bodges around now...

                  Comment


                    Re: Fixing a laboratory waterbath

                    Originally posted by eccerr0r View Post
                    It's not the temperature range of the bath that's the problem, the phase change motor's vibration is what kills electronics. I'd suspecting it's what killed your connectors in the first place, and perhaps if that avenue was checked first, there wouldn't be so many bodges around now...
                    That is likely why it worked for a week. I ve been doing a lot of things wrong since I opened this thing a few weeks ago. Even with all these issues I get excited about this and look forward to working on it and understanding better how these circuits work. I think I ve found myself a new hobby. And of course, as I ve said before, I m really appreciative of you guys taking some of your time to help me even after half of these issues I ve caused myself.

                    Comment


                      Re: Fixing a laboratory waterbath

                      btw how the heck do you get a water bath to 120°C, is it pressurized water?

                      Comment


                        Re: Fixing a laboratory waterbath

                        To keep it liquid at 120°C, you must increase pressure to at least 200 kPa (so around 100 kPa gauge pressure).

                        Comment


                          Re: Fixing a laboratory waterbath

                          Originally posted by eccerr0r View Post
                          btw how the heck do you get a water bath to 120°C, is it pressurized water?
                          Originally posted by petehall347 View Post
                          To keep it liquid at 120°C, you must increase pressure to at least 200 kPa (so around 100 kPa gauge pressure).
                          No pressure here. We use a mixture of water and anti-freeze. It allows us to get to temperatures below 0 and a bit higher than 100 °C. We almost never use it at such high temps anyways. If we wanted to we d have to use another mixture. We do use it at temperatures below 0 though.

                          Yesterday I made myself a small current limiter setup with a 100w bulb. I tried it today with the waterbath. The waterbath starts and runs but the display is dim and the pump fan turns slower than it should. Also the bulb is bright. I suppose it needs more amps to run properly.

                          Tomorrow I ll try with 2 bulbs or more. If I understand well, if I can get to a point where the bulbs are dim and not at full brightness, I can confidently assume that there is no short. Otherwise, if after adding a few bulbs they re still really bright there is probably a short. I don't know how many amps the load normaly takes but since there is a heating element I think it's likely at least a few amps. What do you think?
                          Attached Files

                          Comment


                            Re: Fixing a laboratory waterbath

                            Yes unless you have to many lights bulbs then would almost as though you were using a fuse
                            9 PC LCD Monitor
                            6 LCD Flat Screen TV
                            30 Desk Top Switching Power Supply
                            10 Battery Charger Switching Power Supply for Power Tool
                            6 18v Lithium Battery Power Boards for Tool Battery Packs
                            1 XBox 360 Switching Power Supply and M Board
                            25 Servo Drives 220/460 3 Phase
                            6 De-soldering Station Switching Power Supply 1 Power Supply
                            1 Dell Mother Board
                            15 Computer Power Supply
                            1 HP Printer Supply & Control Board * lighting finished it *


                            These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                            1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                            2 Hem Saw Computer Stack Board

                            All of these had CAPs POOF
                            All of the mosfet that are taken out by bad caps

                            Comment


                              Re: Fixing a laboratory waterbath

                              I tried with 3 bulbs this morning. They all light up. I dont think they re at their full brightness but I m not 100% positive. They do get very hot.

                              I noticed the voltage drop across the primary of the transformer is about 65v. Is it normal for these bulbs to drop the voltage by that much?

                              The waterbath temperature increased by 0.5 degrees in 20 min. So it slowly heats up which would make sense with the limited amps and lower voltage.

                              I m not confident everything is working well enough to plug it without the bulbs.
                              Attached Files
                              Last edited by vrasp; 07-21-2021, 07:35 AM.

                              Comment


                                Re: Fixing a laboratory waterbath

                                It's up to you to decide what's going on... especially when dealing with heaters and other things that draw a lot of power.

                                Comment


                                  Re: Fixing a laboratory waterbath

                                  I plugged waterbath straight into the wall without the bulbs in series. The TRIAC blew again. It was not grounded, I checked.

                                  These are the observations I made:

                                  The resistance between where MT1 and MT2 connect have a low resistance (even with no TRIAC connnected). Based on my reading, it is supposed to have a high resistance. From now on I ll refer to where MT1 and MT2 connect as MT1 and MT2 to make things easier. MT1 connects to the heating element. It's the live of that heating element and then there is a neutral wire that goes from the heating element to the PCB. MT2 connects to 120V.

                                  I removed the heating element cable from MT1 and the resistance between MT1 and MT2 became very high, which makes sense since MT1 is only connected to that. Could a faulty heating element cause that? I don't see how but I don't know.

                                  Any ideas?

                                  Thank you!
                                  Last edited by vrasp; 07-21-2021, 03:16 PM.

                                  Comment


                                    Re: Fixing a laboratory waterbath

                                    Or there is a very low resistance between neutral and live. I ll check that.

                                    Comment


                                      Re: Fixing a laboratory waterbath

                                      If the heater element is like the type in a water heater then you need to check the outer case to the terminal of the heater element and you should NOT get any resistance if you do have any resistance then there is an issue with the heater element

                                      What is the resistance of the heater element because if it is for 120 volts then the resistance can not be extremely low because if this might be your problem ( it should be around 8 to 10 ohms )

                                      This also depends on the tirac amperage rating if it lower than 15 amps then your resistance would be higher than 10 ohms
                                      Last edited by sam_sam_sam; 07-21-2021, 04:17 PM.
                                      9 PC LCD Monitor
                                      6 LCD Flat Screen TV
                                      30 Desk Top Switching Power Supply
                                      10 Battery Charger Switching Power Supply for Power Tool
                                      6 18v Lithium Battery Power Boards for Tool Battery Packs
                                      1 XBox 360 Switching Power Supply and M Board
                                      25 Servo Drives 220/460 3 Phase
                                      6 De-soldering Station Switching Power Supply 1 Power Supply
                                      1 Dell Mother Board
                                      15 Computer Power Supply
                                      1 HP Printer Supply & Control Board * lighting finished it *


                                      These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                                      1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                                      2 Hem Saw Computer Stack Board

                                      All of these had CAPs POOF
                                      All of the mosfet that are taken out by bad caps

                                      Comment


                                        Re: Fixing a laboratory waterbath

                                        Thanks. I ll check that.

                                        Comment


                                          Re: Fixing a laboratory waterbath

                                          I actually had already checked the heating element with ground and it was fine. All three terminals had high resistance with ground.

                                          I m thinking of everything thats on the board. I ve already removed the capacitor. I m pretty sure it s not the transformer. I can try removing it. The rest are part of the circuit that feeds the pcb below it so not related to the actual heating.

                                          Isn't a heating element just a thick tube of copper/alloy with a high current going through it? How could it be faulty?

                                          Below is a photo of the board I ve posted before.

                                          Next to the number "12" is in order

                                          Gate
                                          MT2
                                          MT1

                                          I made a mistake in my previous post. MT1 terminal is connected to the heater element and MT2 terminal to 120V. Either way, there is continuity between them where there shouldn't be.
                                          Attached Files
                                          Last edited by vrasp; 07-21-2021, 08:02 PM.

                                          Comment

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