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  • #16
    Not sure if Gocha is still reading this thread, but I learned a bit today...

    ​​​​​​Here are the components that control the HF circuit. In the middle (blue box), is the HF continuous/start/off switch. 115V AC is across it anytime the primary contactor W is closed (contactor control in STD or remote with pedal depressed). When it's in start, it's connected through a normally open (NO) connection on CR2. So it will only work when the CR2 relay is energized. The red box shows the circuit that energizes CR2. That secondary coil is charged to 115V anytime the power switch is on (and circuit breaker not tripped). That circuit basically energizes CR2 through one of two relays - relay CR1 is normally open, but powers the coil on CR2 when it is energized. Relay CR3 is normally closed and provides power to CR2 whenever the contactor control is in remote and the pedal is NOT pressed. The green box on the right shows how relay CR1 is energized - basically when the output is not welding and the primary contactor W is closed.

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    A close up of the blue box shows the switch. Relay CR2 (red box) closes the HF primary coil when it is energized (refered to as picked up in the Miller manual), and disconnects the HF primary when it is not energized.
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    A close up the red box from the first picture shows the CR2 relay energizer circuit. Relay CR2 (red box below) is a DC relay coil, so rectifier SR4 rectifies the 115V AC to DC, with C4 and R9 (all in blue box below) smoothing out the DC, as well as storing some charge to delay CR2's turn off (called drop out in the Miller manual) once it's disconnected from the 115V AC. Relays CR1 and CR3 (green box below) ​​​​​ control when CR2 coil is connected/disconnected to the 115V AC. Relay CR3 only controls the circuit when the contactor control is switched to remote (switch S4 in the pic is the contactor selector switch). CR3 is normally closed, so it only energizes CR2 when the pedal is not pressed (and contactor set to remote). It doesn't cause HF on the output because the primary contactor W is open and not powering the output or the HF primary coil when S4 is set to remote and the pedal is not pressed. It took me a while to realize CR3 is in this circuit because it pre-charges C4 so there is no delay in HF when the pedal is pressed. CR1 is normally open, and energizes CR2 when the CR1 coil is energized. So in this circuit, relay CR3 and CR1 are in parallel and either one can energize relay CR2.

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    Below you can see how relay CR1 (red box below) is energized. It is a 12V DC relay coil. The output voltage (up to 80V AC) is split by the variable resistor R2 and rectified to DC by rectifier SR2 (blue box below). So it turns on anytime the output voltage goes above a certain value. I don't know that value, but would guess it's somewhere above 40V and below the 80V open circuit voltage.

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    That's why I asked Ryan if HF worked when the contactor switch was in standard and the HF switch set to start. As I understand the circuit, the HF can only start when the primary contactor W is energized (pedal pressed in remote contactor or always in standard contactor), and then will always be on in HF continuous, or when the arc is not struck in HF Start.
    Last edited by jjohn76; 10-08-2019, 08:54 PM.

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    • #17
      This is from one of the earlier Miller 330 A/BP manuals. The left is for standard contactor. The right is for start in HF remote. You can see the only time CR2 is not energized is some delay after the arc is extinguished (assuming if in remote contactor, the pedal is still held). In the left diagram I think there is an error in the manual for the start current relay (CR4), which selects either R7 or R8 as the current reference. It should match the right diagram, with CR4 energizing (picking up) with power switch on.

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      • #18
        Last post... Which shows the relays to check (CR1 on left and CR2 on right). When there is open circuit at the output leads, CR1 should switch on. Check to see CR1 opens and closes when you step on the pedal. CR2 should go from open to close when you power on the machine, whether in STD or remote contactor.

        Older 330 similar to Ryan's
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        "Newer" model
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        Last edited by jjohn76; 10-08-2019, 10:32 PM.

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        • #19
          Yes I'm still watching my welder is an 1988. I wanted to say it starts on AC but not DC. I talked to the Miller dealers repair guy he just wanted to order a H/F transformer but I would I would like to know for sure what's wrong. I checked the black capacitor with one side disconnected and it had no resistance or continuity the repair guy said that it was good I don't know what it should read. I haven't checked the H/F switch yet everything inside the right panel looks like new. Thanks for all the replays.
          Last edited by Gocha Ent. Inc.; 10-09-2019, 08:57 PM.

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          • #20
            Gocha, are you talking about the capacitor in the HF circuit down by the start timer and gas/water valves? That and the HF transformer are good if it works on HF continuous. Your problem is either at the HF switch on the front panel, the relays on the right side, or the wiring in between. If the components on the right side are new, you should be able to see the relays actuate through their clear covers (1988 is the new model). The quickest check is to watch the top two relays when you power on the machine and when you turn on the primary contactor (press the pedal). The top right relay should click when you turn on the power switch. The top left relay should click when you press the pedal. Does this happen?

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            • #21
              I'll get the side panel off tomorrow and check thanks.

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              • #22
                Originally posted by Gocha Ent. Inc. View Post
                I'll get the side panel off tomorrow and check thanks.
                Sounds good. Hopefully my post #20 above makes sense. It is from one of the very early manuals and tells you what the relays should do depending on your settings.

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                • #23
                  Mine is a 74 model. But if it will help, I can pop the skin off and poke around in it. Not sure what I’d accomplish, but it’s the thought that counts, right?

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                  • #24
                    jjohn76 jjohn76

                    The top right relay doesn't click when I turn on the power the top left does click when I step on the pedal.

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                    • #25
                      Originally posted by Gocha Ent. Inc. View Post
                      [IMG2=JSON]{"alt":"jjohn76","data-align":"none","data-size":"full","title":"jjohn76","src":"https:\/\/forum.millerwelds.com\/core\/avatars\/0\/0\/3\/9\/5\/0\/\/thumbs\/avatar75766609_2.jpg"**[/IMG2] jjohn76

                      The top right relay doesn't click when I turn on the power the top left does click when I step on the pedal.
                      Gocha, does the top right relay click on when you press the pedal? If not, it means either power isn't getting to relay CR2 or relay CR2 is bad. It's probably difficult to get a multimeter on the relay coil inputs. The relay connectors should look similar to this

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                      When you turn in the machine, the upper right relay (CR2) have about 163V DC across the bottom left and bottom right terminals (in this picture). The coil input terminals usually look different than the rest. In this picture, they are rotated 90 degrees. In others, they tend to be spaced away from the others.

                      If you can't access the CR2 connectors or can't tell which two are the coil inputs (they are usually separated from the group), then you can check voltage across rectifier SR4. Right above the right relay, you should see the SR4 rectifier, which looks like this
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                      You should see which corner says + or - . Measure the DC voltage across the diagonal connectors with the machine on (should be 163V DC). If you get 0V, check that same diagonal in AC (you may have measured the AC input terminals). If you get ~120V AC, then measure the other diagonal in DC, and you should get ~163V DC.
                      ​​​​​

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                      • #26
                        Ok I'll check it tomorrow

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                        • #27
                          Originally posted by Gocha Ent. Inc. View Post
                          Ok I'll check it tomorrow
                          Sounds good, please be careful checking the 163V DC, as it can be lethal voltage.
                          Last edited by jjohn76; 10-11-2019, 06:23 AM.

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                          • #28

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                            • #29
                              jjohn76 My CR-2 is a little different all the terminals face the same direction.

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                              • #30
                                Originally posted by Gocha Ent. Inc. View Post
                                jjohn76 My CR-2 is a little different all the terminals face the same direction.
                                Ok, one is the one on the right side as you took the picture, it should be the closest terminal to the panel. The other one is directly to the left of it. Hopefully that makes sense.

                                If you can read the numbers on the wires it should be 63 (+) and 64 (-).
                                Last edited by jjohn76; 10-11-2019, 02:34 PM.

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