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Thread: Relay Repair

  1. #21
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    When I bought my R2C3 CNC it had mostly sat
    The main power relay, a big self holding job was flaky

    I took a needle file and carefully cleaned the contacts and it has been flawless for 28 years

  2. #22
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    If it were me, first thing I would check is the contact block, on the back of the selector selector switch.
    The contact blocks have a spring return, when you actuate the switch. If the plunger on the contact block switch is gummy, the tiny spring may not have enough force to move the plunger, until it has time to overcome the stickiness.

    Cleaning it with some contact cleaner, may be all you need. It's a lot easier than removing and disassembling contactors for cleaning.

    SAF Ω

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  4. #23
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    Quote Originally Posted by rbdjr59 View Post
    The machine stays stuck in the head mode. I know just enough about electronics to make me dangerous but it seems to me that one of these relays is sticking and not letting the machine switch. I'm thinking I need to go in there and clean up/refurbish as able these two relays and see if it will stay working. FYI, the machine works fine for a couple of days and then locks up. A couple of days later it magically begins to work again! The switch in question is on the top row, 4th. switch. Attachment 287553 I am aware of the complexity of this machine as to the interlocks and limit switches but am praying that the problem is these relays. I have cleaned and exercised all of the easy stuff all ready so we will see. thanks again for the help.
    The issue isn't really "electronic". At root-cause CORE ..it is physical.

    Here's one of the world's worst-ever examples, 'coz you have a very similar situation going-on;

    Akai, Japan sold an open-reel tape recorder/player, late 1960's that I found attractive because it had in one compact and easily toted case all of: 1 7/8 IPS, 3 3/4 IPS, 7 1/2 IPS, and "studio grade" 15 IPS in one case that ALSO had 1 7/8 IPS, 3 3/4 IPS and 7 1/2 IPS 8-track tape in the side of it.

    Problem was... that in order to switch the FOUR motor speeds (plus OFF) and stereo I/O audio, they PRINTED a whole slew of copper pads on a printed circuit board, then put a slider plate over top of it with a whole tribe of sort-of-springy-for-while contact fingers whose anchors were ALSO part of a complex printed circuit board pattern.

    I'm sure it "seemed like a good idea at the time" as far as keeping wiring costs and chance of error down, but... AS and WHEN each of the tribe of pads and contacts corroded or wore, it got progressively less predictable.

    Toward 'end of life' it was SOP to run the switch through all option positions for about 20 or 30 cyles before even powering-on. May as well have been winding the clock-spring on an old mechanical Victrola or the inertial starter of a P-40 warbird for all the delay before the "entertainment" could begin.

    The message in that is that your relays MAY not even be the least bit wonkey.

    It is more likely that whatever switching - manual or position-sensing PLUS any remote "mode" or safety interlocking switch sensors AND their wiring and its terminations - that CONTROL the relays is at least 50% likely to be at fault, if not 90% or 100% percent. The symptom you describe? It needs as little as just ONE bad-actor. ONE. Yah. There could be more. But ONE is all it takes.

    Look there first! Find the Mike Foxtrot. Fix it.


    Then we can each drink our OWN choice of beverages ..and mumble the "War Stories" into the Wife's golf bag ....when she ain't at home?

    Wouldn't want her feelin' the need of lockin' yah up in a stainit-whorie-yum for dirty-walking whilst silly-talking wuddja?


  5. #24
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    The ONE MOST IMPORTANT ACTION when looking at one of these issues is to look into it and find the actual part that is not working.

    Guesses are just that, and you do not want to make large decisions involving much work and/or money on guesses. You want to know what the issue is, so you can decide what to do.

    To find problems, that you need a diagram of the circuits, which hopefully you can locate if you do not have one. With that you can identify the parts you need to check. Without it you either draw your own by examination of the machine, or you are back to guesses.

    Then, you may need to operate stuff with covers open. it is best to fab up some simple brackets to hold any covers that include controls or lights. That saves many hassles and avoids inadvertent shorts and damage.

    A very useful item for 120/240V controls is an old-time neon circuit tester that will take the control volts. Two of them can be even better, for things where one thing goes off and another is supposed to start up. They do not use enough current to falsely operate anything, but they will indicate presence or absence of voltage very nicely, and you can be somewhere else pushing the buttons, etc, so long as you can see the light. Better than a meter sometimes.

    If you cannot get those, then neon pilot lights good for the voltage are just as good. You do NOT want an incandescent type, but some of the LED ones might work in many cases. You need lights that do not draw currents that might operate anything.

    Clip a light across the problem switch. Make sure the light goes out when you press the button (switch makes contact). If OK, check power to the relay coil,(clip across that).

    You can check everything in the string of switches and interlocks as you operate the controls. If the light is across a switch that is supposed to be closed, and the light is on, then either you have it connected wrong, or the switch is not working.

    If the light is across something that should have power, or should be open with voltage across it, and the light is not on, then either you are wrongly connected/not making good contact, or there is a fault.

    If your light is good for the power voltage, you can check that as well, to see if the power relays are connecting properly.

    That sort of problem tracing should get you to the answer fairly quickly, if you can identify the various switches etc that you need to check.

    Don't forget that wires break, they get flexed or stretched and can break inside the insulation, so they look fine unless you know what to look for.

    Once you KNOW what is not working, you can make the decision as to "I can fix that", or "it all needs ripped out and replaced" intelligently knowing what is wrong, having a sensible assessment of what can be done and how much trouble it is to do.

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  7. #25
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    I am beginning to understand about how it is more likely to be a switch causing my problem than the relays. Switch in control panel is a little complicated when you are used to single pole.152.jpg159.jpg

  8. #26
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    Quote Originally Posted by hermetic View Post
    "the machine has a switch that changes the feed/rapid function from the spindle head (up/down) to the table (left/right). The problem occurs when I switch from the table to the head and then back to the table. The machine stays stuck in the head mode."

    Then the problem is the switch, not the relays!!
    Further to my post quoted above, If the up down head feed, and the left right table feed work, that proves that there is nothing wrong with the relays, all the relay does is start the motor by switching the power simultaeneously on all three phases (or whatever the power system is) If there was a fault with the relays, the motor would not run, or would hum and run slowly. The problem lies in the switch that controls the relays, and switches between the head and the table, seems like you could check the switch with a mains power tester if you feel confident doing this. The changeover switch is not swapping the supply from the head relay to the table relay. I cannot go any further as I am not familiar with this particular machine, hope you get it sorted!
    Phil
    East Yorkshire, UK

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  10. #27
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    Feeling confident is not how I would describe my attitude right now! It has occurred to me that I might want to look over the shoulder of someone more qualified to check these switches. I've got a line on a Electrical Guru who is coming over to take a look. We'll see. Thanks for all of the good advice.

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  12. #28
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    Ok, after much study and manipulation to understand how machine functions we found the problem, burnt coil on relay. Temporary fix with modern coil. Old/new relay on the way, but first must go to refurbish shop for cleaning and inspection. Big sigh of relief!018.jpg017.jpg

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