Testing Part of a switch?

Discussion in 'General Electronics Chat' started by duke46, Feb 24, 2013.

  1. duke46

    Thread Starter New Member

    Feb 24, 2013
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    I am almost feeling kind of dumb at this moment because I do know some about electronics and testing some parts but this switch has stumped me when testing with my ohm meter.

    The switch is a two part push/pull. The front part operates the KV voltage of my unit with the switch pushed in. The rear part of the switch operates the uA of my unit and between the two adjustments you have control of how the powder sticks to the metal part I am coating.

    From time to time my settings for the KV want light up and after messing with the switch it will work like it should?

    If I try to raise my uA's up then they will just drop and I will have to turn the knob back and start again. I can not get it to go as high as I need it to do sometimes. There might also be something wrong on my circuit board but I want to figure out this switch first and if it is bad then I can replace it.

    On the back of the switch there are 4 lugs. Two of them are wired and the other two are not and I have tested them and they are separate from each other. When I test with the meter they test the same. They might start out with the ohm meter reading .6 and then go to .2 or .1 and when turning the knob I am seeing no change in the readings? If I cut the unit on and pull the knob to activate that part of the switch I can adjust the uA but just not as much as I need.

    I am accustomed to seeing more movement of ohms when using an ohm meter than I am getting and at this point not getting any. Is it me or is it the switch and the switch just wont read like I think it should? I can not make out the numbers on the switch so can't try to look it up. Looking at the info and picture for the org switch this one has been replaced I think? This unit is old and finding parts is not going to be easy and the part numbers for this switch are not to be found except one that sold on eBay a few years back.

    Here is a picture of the switch if tha helps anyone.

    Thanks
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,363
    This is a potentiometer with a switch attached to the rare.

    The potentiometer adjusts the voltage setting, regardless of whether the switch is pulled out or pushed in.

    The switch is used to switch between displaying the voltage or current.
    When the switch is pushed in, the display shows voltage.
    When the switch is pulled out, the display shows current.

    There is nothing wrong with the switch or control.

    Something is wrong with the circuit and the power supply is shutting down when too much current is drawn.
     
    Last edited: Feb 24, 2013
  3. tubeguy

    Well-Known Member

    Nov 3, 2012
    1,157
    197
    The switch is also a potentiometer, or 'pot'. - The gold section with the 3 terminals (white and 2 blue wires).
    With the unit OFF and disconnected from AC power, you may be able to clean it -- spray bit of pot cleaner in the slot by the 3 wires and gently rotate it fully back and forth.

    Edit I type slow :)
     
  4. sheldons

    Active Member

    Oct 26, 2011
    616
    101
    if the switch section or potentiometer section has become noisy or intermittent a squirt of switch cleaner will cure it -if not you need to look elsewhere for the fault
     
  5. duke46

    Thread Starter New Member

    Feb 24, 2013
    5
    0
    OK you woke up the DUH part of my brain on that one. So the back part of this switch just operates what is showing on the meter. In this case it is a row of lights. And you read whatever side needed with it pulled out or pushed in.

    I have once before used the tuner cleaner on the pot but maybe a year ago. The unit is sealed and after I cleaned it I had less trouble. Now where in heck did I put my darn cleaner?????

    Something tells me that either it is getting wore out and needs replacing or I do have a problem else where on the circuit board.

    With it age the replacement or repair of the board might not be feasible but replace the pot should be doable. I could even install a pot and a switch. There is room.

    Well I guess I will start calling and see if I can find the companies that use to repair them. The company that makes them does not service the older items. This unit is made by ITW Gema and it was priced over $2500 when new and newer one can be double that but they have really updated them from the mid 90's

    I am 68 and not interested in laying out that kind of money now days.:(

    Thanks for your help guys. And I should have know the answer to my question to start with but went totally brain dead this time.
     
  6. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,363
    There could be a dead spot on the pot. See if you can measure the maximum resistance of the pot.
    Ask if you do not know how to do this.
     
  7. duke46

    Thread Starter New Member

    Feb 24, 2013
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    0
    Well I think I understand what you are asking I should anyway???

    Now I have not unsoldered the wires so that could affect the readings. But I did find something that does not seem right?

    I am using a Fluke 27

    With knob all the way to left and connected to the white wire and center blue I read 16.0 and and as I turn clockwise it reads to 222.5 and just past 9:00 it goes to 0 and at 10:00 starts at .355 and goes to 2.101 at stop

    With knob back to left and connected to the blue wires and turning clockwise it reads 2.094 and then goes down to .335 and at 4:00 does the 0 again and then just past that it starts at 254.00 and starts heading down again to 6.2 at the end

    What is going on with it going to 0?? Even with it still wired in I would think it should not do that? Or should I at least unsolder the center blue wire? Unit is off and unplugged so there is no current but there is the circuit.
     
  8. panic mode

    Senior Member

    Oct 10, 2011
    1,321
    304
    remove at least 2 wires and try again. if you are getting dead spots, potentiometer is likely burnt in those places. also use units. i don't know what you mean by "it reads 222.5" because there is no unit mentioned (Ohm, kOhm, MOhm,...).
     
  9. duke46

    Thread Starter New Member

    Feb 24, 2013
    5
    0

    Sorry but the readings are Ohm's

    I guess it would be best to remove the two outside wires then all I will read will be the pot.
    Thanks
     
  10. duke46

    Thread Starter New Member

    Feb 24, 2013
    5
    0
    Readings did not change any with the two outside wires removed. And the drop out to 0 was at the same places.

    the pot is a 2k2-A-0.25 it has a 97-04 there is something in the middle of the two number but can not make it out.

    I soldered the two wires back and then cut the unit on.

    The KV side with the switch pushed in went to 60 kv. and went through the 0 area but keep climbing?

    I pulled the switch out and the uA would go to 40 uA's and that was its max but it never dropped out if I tried to go past it like it did before.

    With the uA's set at 40 and then switch back to the KV setting I was maxed at 100KV. When I would turn the KV down to 50 or lower then the uA would also drop. I will have to start asking some questions to the guys that have a older unit like this on my powder coating forum.

    Right this minute the pot seems to be working but that could change anytime like it has before. I have not sprayed any tuner spray in it yet. Still can't figure out where I put the dag can:confused:

    Well time for me to get on the phone and see what I can find because I don't even know where to start as for as a replacement for at least the pot part of it. Heck a toggle switch would take care of the switch part. Any info you guys have would be great.
    Thanks
     
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