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Newbie question on 50 year old pottery wheel

Discussion in 'Troubleshooting and Repair' started by budster, Dec 30, 2020.

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  1. budster

    budster

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    Dec 30, 2020
    Hello all, first post here and I'll start by saying that my knowledge of electronics is really very basic. I can take stuff apart, look for anything obviously broken and (badly) solder but beyond that I am lost. Please pitch replies as if you were talking to a 10 year old. Not even a particularly bright 10 year old.

    My wife has recently acquired a pottery wheel which, on closer inspection, appears to date from the early 70s. Apparently it was working before being moved and now isn't, so I thought it was worth taking apart to look for anything obvious.
    I think I have found the component at fault but am now stuck as I don't actually know what the component is or what to try next. I have attached a picture of it.
    When the power is applied and a switch elsewhere on the machine is pressed, I believe the contacts on this should flip over (up in the picture) and complete the circuit, suppling power to the motor which is then driven by the pedal. In reality, nothing happens.
    If I push this component up manually, it will click on and stay on and pushing the pedal will then operate the motor. Happy days.
    However, when the power is cut, it clicks off again. and the only way to get it going is to manually push this component again to complete the circuit.
    None of the wires on this component itself are loose, nor are any of the other wires, as far as I can see.
    Any thoughts on a) what is this component? b) is it repairable / replaceable? c) is it easier just to bypass it?
    Thanks in advance.
     

    Attached Files:

  2. Minder

    Minder

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    Apr 24, 2015
    You would need to trace the circuit out, what is the manufacturer?
    I assume it has the normal footpedal control, is it speed controllable?
    M.
     
  3. Bluejets

    Bluejets

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    Oct 5, 2014
    Add to M's comments....if you push the relay manually and it stays on, then it is wired as a hold-in relay.
    Don't know why but perhaps there was a momentary contact push button in the coil circuit previously which would do the same thing without having to poke around the dangers of high voltage as you are doing now.
    As M says, trace out and draw a sketch of what connects where.

    Below is a typical latching relay circuit. In this, when the button is pressed and then released
    ( momentary), the coil activates and closes both sets of normally open contacts. The first set is wired to "hold-in" the relay until such time as power is conpletely removed.
    The second set of contacts can then be used to operate another device such as your motor circuit.

    Typical latching relay.jpg
     
    Last edited: Dec 30, 2020
  4. 73's de Edd

    73's de Edd

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    Aug 21, 2015
    Sir budster . . . . .

    Try this . . . on that power relay, as it will cost nothing to try.
    .In the most frontal foreground, you can see that those two contacts have nothing soldered to them, while your two AC power connections come in from the two looped in uber flexible braided wires with their white insulative coverings.
    Each one is then soldered to its respective flexible phosphor bronze leaf which has a double sided contact a its end.
    We have seen that the two ones facing us are being unused but the ones that are wired to the white and brown wires carry power down to your motor.. . . .etc.
    This is considering that power . . . likely . . . .AC voltage . . . . . is applied to both the violet wire and the identically positioned wire just BELOW it, which seems to be a pale blue.
    Now that short visible enameled brown copper wire run between the violet terminal and the black coil seems to be of too LARGE of a guage to be totally wound to fill up the black coils bobbin and to then be powered by 230 VAC for its power . . . . . unless there is being a transition under the black covering of connecting into and then the use of a much finer / gauge wire for the coil winding. That wire gauge seen is more in order of use of a 24VAC power level to power the coil to pull in the relay armature with the two leaf contacts, bringing them into contact with the inner pair of contacts and their conective white and brown wires, going over to your equipments end ( motor + ? )..

    Now you need to see if you have a miniature flat file from your Swiss patttern.tool and die set . . .or . . .grand dads ignition file that he used on the Model T Fords ignition points . . .or . . .Mamma Cass's diamond dust encrusted nail file . . .or her CHEEEEEP emory board nail files . . . . .or . . . . in YOUR stuffs . . . .wet 'n dry silicon carbide paper of 400-600 grit upwards . . .or (shudder) sandpaper types of fine or ultra fine grit . . .or emory cloth . . . . from your copper pipe cleaning and soldering escapades . . .or . . .?
    You are then wanting to insert your cleaning weapon of choice between the leaf contact and the inner contact and maintain a pressure while cleaning in an up and down motion.
    Or . .. .pull strips of the wimpy flexible types of cleaners thru in a single direction and then again with the abrasive side facing the other contact side . . . . taking 4 swaps . . .or more . . . in cleaning all 4 sides of the contact pairs.. This should hopefully get the presently erose, oxidized, pitted surfaces of contact arcing and created pitting in the silver contacts, back to having MUCH better, fresh metal, shiny contact surfaces.
    You can see that one visible inner contacts side that is closest to the copper wire has a deep black silver oxide deposit upon it . . .vice shiny silver.
    And then, you can just BARELY see some exposed raw silver, being at its center, towards its companion leaf contact .

    A one upmanship would now be to also comandeer one of Mamma Cass's standard table knives and do the same up and down movement between the relay contacts, with them being being pressed together . This will then smooth/compress/polish the contacts surfactal metal and provide better / low ohmic contact than will the present conditiond matte surface, as being left by the prior abrading down to prime metal again. Also, it makes those contacts less likely of probability to arc and sticking or fusing together.

    So o o o o o o o if you were to plug the unit in and do your prior power up procedure and you hear that relay armatures SNAP in, I now would expect your cleaned contacts to now pass power downstream and make your equipment work . . . . . . until you turn it off and hear the relay snap again, as its armature releases contact tension.

    The way it was initially, I believe that you detected both relay states noises but one or both of the worked on contacts was then so boogered up, such that GOOD electrical contact was not being made.

    I can't POSITIVELY see ALL of your relays wiring connections . . . except for piss poor YELLOW, VIOLET and WHITE solder connections . . . . . but for all youse other guys, sitting up thar in the peanut gallery . . . . here are more views of that specific KMK2 series of relay.

    https://www.ebid.net/us/for-sale/relay-keyswitch-kmk-2-230v-ac-2p-c-o-20569-new-boxed-153702122.htm


    Know whuts . . . . . . . .thaaaaassssit. . . . . . .

    73's de Edd . . . . .

    (This one's for you Martaine )
    I just totally being bamboozled and flabbergasted in my understanding of how I got over the hill ! . . . . . without my ever being on top.

    .
     
    Last edited: Dec 31, 2020
  5. budster

    budster

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    Dec 30, 2020
    Thanks for all the replies. Haven't had the chance to look at this today, will try tomorrow and get more photos or sketch how it all connects and give 73's suggestion a go.
    Good work on the ebay find. I did google KMK2 without success but the addition of the space obviously makes all the difference.
     
  6. budster

    budster

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    Dec 30, 2020
    Evening all, I've had the chance to have more of a look at this today. Attached is a schematic of the wiring. I haven't shown the wiring on the "business" side of the relay but can add that if useful.
    Also attached are some more pictures to show wider context.
    Looking at that, it is still the likeliest thing that the relay could be at fault? Or could it be the push switch?
    Potters wheel wiring.jpg wheel circuit annotated.jpg wheel front annotated.jpg Potters wheel wiring.jpg wheel circuit annotated.jpg wheel front annotated.jpg
     
  7. budster

    budster

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    Dec 30, 2020
    I gave the contacts a good a clean as I could manage; found some 800 grade paper (not sure what type). The paper came out grubby but still no joy, unfortunately.

    I see that relay on ebid that you have linked above is only about a fiver. Is it worth a punt, do you think, replacing it?
    Is a relay a part that has a limited lifespan?
     
  8. Bluejets

    Bluejets

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    Oct 5, 2014
    Is the push switch momentary or does it click on and click off...??

    One part of it should at least be momentary and going by the latch contact on the relay I'm guessing momentary should be from the grey to the brown on the push switch, primarily because you say you push the relay in by hand and it latches and the unit runs.

    Diagram below shows what I think to be the arrangement.
    Power on, push button and the momentary closes along with the changeover section of the switch.
    Release the push button, momentary opens but power to the coil is now maintained through the relay latch contacts.
    Push the button a second time, momentary closes but no worries as it does nothing BUT at the same time the changeover section now opens and stops the coil from being energised and the relay drops out.

    Switch.jpg

    Relay contacts are one area to check but you've cleaned those and anyhow, the problem is in starting to begin with so I'd say switch problem most likely.
    Cheers Jorgo.
     
  9. 73's de Edd

    73's de Edd

    3,081
    1,301
    Aug 21, 2015
    Sir budster . . . . . . . . . .

    appears to date from the early 70s
    If you look at the black pot in the top corner and its 500 ohm ( unless that 4th symbol is not being an ohm symbol and is being another 0 ), then making it a 5000 ohm pot.
    BUT it is ALSO telling you that the pot was made the 37th week of 1972 . . .with a further white tags dateline supplication of a QC / inspection write off of July 22 of 1973 . . . in merry ole Aingland.( Yet, some of those blue E-caps and other caps icht bin lookink 'CHERMAN and the carbon resistors . . .and HEAVE E E E DUTY HAMLIN reed switches as being of AMERIKANSKI sourcing.

    When the power is applied and a switch elsewhere on the machine is pressed, I believe the contacts on this should flip over (up in the picture) and complete the circuit, suppling power to the motor which is then driven by the pedal. In reality, nothing happens.
    If I push this component up manually, it will click on and stay on and pushing the pedal will then operate the motor. Happy days.
    However, when the power is cut, it clicks off again. and the only way to get it going is to manually push this component again to complete the circuit.

    and . . . .

    I see that relay on ebid that you have linked above is only about a fiver. Is it worth a punt, do you think, replacing it?


    That tells us that your relay is working fine . . . . . now even MORESO . . . .since you have assured clean contacts on it.
    It is just that initial latching in of the coil of that relay to be constantly powered up, that is yet to be figured out .
    Do you have a voltohmmeter to check for AC and DC voltages or if being unpowered, doing an ohms check of components and opened wiring ?

    Your forthcoming info . . . .
    Now in the bottom left corner you have marked in a "back of pedal rotary switch"
    By its size and beefiness, I also want to believe that as also being a wirewound pot with an attached black snap on switch as being the two paired YELLOW wires.
    See if its ohms of resistance is being stamped / marked on it also.
    Then, I see that its frontal potentiometer portion has a white wire soldered onto a terminal at its frontal shafts extreme CCW position with another yellow being wire soldered onto its central terminal rotor connection, then that internal rotor can fully rotate to its extreme full CW position throughout a total 270 degrees of rotation and then be resting against the violet wires connection terminal.
    With that elecro-mechanical aspect now explained, will you confirm if the pot and switch is now mechnically interconnected to the 30% gear segment and its intermeshed full gear that it spins . . . on the opposite side ? I'm expecting, to the small gear with its full toothed periphery.
    If so, is the small black 500? ohm pot being the small shaft end and its control nut, also seen with the shafts slotted screwdriver adjustment . . .that is seen as almost touching your floating ground terminals green wire ?.

    If so does your foot pedal rotate from a central pivot point such that it stays at the foots last slanted position before then being lifted.
    For a needed speed change you then rock forward slant ? with the foot for faster, or rock back? for slower speed . . .OR . . . . . . full backwards for slowest speed and then the final extreme limit for auto clicking of the switch for turning off ? ?? ?
    Then the way I am seeing the inter wiring connections of those two pots being, has the speed controllable up to max floorboarding speed with the foot, but, by readjusting its factory set limit of the slotted 500 ohm pot shaft end, permits a bit MORE ( or less) max speed, with its adjustment . . . .we just don't want clay being slung all over the walls at excess speed..

    Now you dave done GREAT on info submitted that I am able see all views of, but your titling of Foot pedal rotary switch should relate to an item having 5 connections and the proper wiring to it.
    Then the titling of the on-off push switch drawing should only have 4 wiring connections being associated with it .
    Also, as der Bluejetster has also inquired . . . I am seeing two separate single pole switches that will only short their connections when fully pushed in, then open those connections when released.

    Now as per that switch that is in an unviewable position to us, I suspicion that some wire colors go into the switch, but then come back from the companion contact of the switch as a different wire color.
    Example . . .
    Take the two paired yellow wires on the bottom switch, both pass upwards but one dissappears into a black grommet at mid point as do the rough corrugated surfaced red-black-orange motor wires . That leaves the other yellow wire to pass on up and solder into one relay terminal. The violet wire connection of one of the relay coil connections goes down and passes thru that same grommet hole to the switch side the unit .
    Can you examine the wire routing and correct those two aspects of main switch and speed sontrol / with ITS switch.
    And, if you can confirm some wires routes for me, I will work out the same thing for you to confirm / check against.

    Does ? :
    The bottom white wire fom the 500 ohm pot get cabled up and pass down to the bottom motor speed pot and
    then break out and then get soldered to the max CCW terminal. Then just to the right I see the center rotor terminal having a yellow wire soldered to it and then that wire is routed over to the very botton of 10 terminal stakes laid uut vertically. Then the pots end with the max CW . . .max speed position . . .receives a violet wire to hide in and out between some wiring and emerge to finally get soldered to the 7th stake up.
    Confirm for me, that violet stakes foil does not spread out and join neither the blue stake above it, nor the orange one below it.
    But it goes straight forward until it ends at an unused drilled holes foil land , but halfways, it branches off upward and has that foil path passing under two black bullet diodes and ends up at a stake that connectcs to a reed relays inner magnetic switch. The coil wound above its bobbin with the fine red wire energiizes the unit.
    You can see the internals as another " naked " magnetic reed at the bottom of the pic, but its coil is being a mere 3 turns of wire coil so it needs a fierce amount of power passing thru it to magnetically activate its reed switch.

    BTW . . .DON"T try to correct that left REAL gold (flashed) reed terminal from its slanted alignment to a perfect " Dress right dress"
    for they are VEWY-VEWY brittle in the glass to lead seal . . . .HIGHLY likely of leaving two pieces in your hand.

    So with the color, violet, of wires still in mind, it looks like that speed pot is dependent upon that reed relay being closed to get its speed control capability, otherwise the control is floating without connection on that end.
    Still on violet *** wires, the only other one I see is being the one on the top open frame relay and connected to its coil and routes across to the left in the bundle and dissapears into the grommet and goes to one front switch terminal and comes back from the companion switch terminal as another color of wire.
    *** Tha top violet wire seems to me, as being of a slightly paler shade than the one down at the pots CW terminal.
    Now for the TOP white wire on the 500 ohm pot, doesn't it enter the bundle and then emerge as the white wire soldered to the 2nd stake up ?
    As for the half horsepower motors three . . . . corrugated surface red-black and orange wires, don't they come in and get connected to the 2nd,3rd and very top 10th stakes ?
    Now for our mid left off center mounted power transformer for the low voltage needs of the board. Do I read a 12V at one ransformer corner?
    As I see it, there two DOUBLE terminals at its top that are receiving a brown hot 230VAC input at its left terminal and then having the right terminal jump over to the ckt board to stake # 9 for getting hot AC into the board.

    The pair of terminals lower down are taking in the AC blue neutral 230VAC into the transformer primary and then using the same other terminal to its side jump over the board to
    stake # 9 for getting AC neutral to the board.

    Now confirm for me that stake 4-5-6 wires go down into that transformer as its secondary wire connections.
    I am " reading" the green wire as being the centet tap of a TOTAL secondary winding, that is either 12VC or 24 VAC that feeds into the 4 diodes to the right of stakes 5 and 6. they then make 6 or 12 VDC power supplies with the blue E-caps. They are not exposing their voltage ratings to my view . . .but I can see the two larger ones as having 220ufd values.

    At this moment no need to travel on further into the right sides power motor speed controller with its two extreme end, stud mounted controller SCR's and gates potted toroidal drivers being on the other side of the sinks and the two small signal ceramic case / epoxy top drop Fairchild units, being only 1/2 visible.
    Since you said . . . .
    pushing the pedal will then operate the motor


    I stop now, awaiting for the wire routing info.

    Read past the points that you do not understand, or can immediately grasp, as I was just passing my full observations to the ILLUMINATA readers.

    73's de Edd . . . . .


    I have always wanted to be a procrastinator, but, seems like I just never got around to it.

    .
     
    Last edited: Jan 2, 2021
  10. budster

    budster

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    Dec 30, 2020
    Thanks for the diagram. Some of it is a bit beyond me, I'm afraid. It looks correct, if I'm understanding it properly.
    I have uploaded some photos of the switch as well. There seems like a lot of wires for just a switch, but there is also a bulb in the green part which comes on and stays on while it is connected to the mains.
    I'm not sure I'm understanding you regarding the "momentary" bit. The switch is a push-in-and-stay-in type i.e it hooks into something when you press it in and then unhooks when you press it again. Apologies again as I don't know the correct terms.

    IMG_20210102_104940.jpg IMG_20210102_104859.jpg IMG_20210102_104913.jpg IMG_20210102_104844.jpg
     
  11. budster

    budster

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    Dec 30, 2020
    Fascinating stuff, I bow down to your superior knowledge! Yes, it is a 500 Ohm resistor. I checked that with a multimeter and that is showing about 480 Ohm, which I assume is fine.

    Indeed I do, but I'm not sure where to put the -ve and +ve terminals on the wires other than on the "obvious" brown and blue AC wires, or offshoots thereof.

    Yes, the beefy silver topped part is marked as 5K Ω.

    For your viewing pleasure, I have loosely reattached the pedal and attached are some pictures showing the gear with the pedal fully up and another showing the pedal fully down.
    The 500Ω pot is not mechanically attached to the pedal mechanism (or anything, for that matter). pedal fully up.jpg pedal fully down.jpg

    LOL, indeed we don't want the clay all over the walls, I've only just repainted.

    I'm not sure I'm quite following your questioning but hopefully the pictures above will largely answer it. I think of the pedal like a throttle in a car basically. Gentle touch on the pedal - low revs, low speed = clay stays where it is. Pedal all the way down = high revs/speed = clay everywhere.

    Do the pictures of the switch attached above in reply to Bluejet answer this question?

    If by max CCW you mean the top terminal shown (left most on the "beefy" section), then yes, that's where that goes. This is the OFF position of the pedal, just to be clear.

    Correct, the violet wire does not spread out to either blue or orange

    My replies in purple [BUDSTER]
    So with the color, violet, of wires still in mind, it looks like that speed pot is dependent upon that reed relay being closed to get its speed control capability, otherwise the control is floating without connection on that end.
    Still on violet *** wires, the only other one I see is being the one on the top open frame relay and connected to its coil and routes across to the left in the bundle and dissapears into the grommet and goes to one front switch terminal and comes back from the companion switch terminal as another color of wire.
    *** Tha top violet wire seems to me, as being of a slightly paler shade than the one down at the pots CW terminal.

    >> Agree, it is a bit lighter colour and gauge.

    Now for the TOP white wire on the 500 ohm pot, doesn't it enter the bundle and then emerge as the white wire soldered to the 2nd stake up ?

    >> Yes. With the red wire also on that stake.

    As for the half horsepower motors three . . . . corrugated surface red-black and orange wires, don't they come in and get connected to the 2nd,3rd and very top 10th stakes ?

    >> Indeedio. I wouldn't say they are corrugated though, I think what you are seeing is where they have been spattered with wet clay since the 70s!

    Now for our mid left off center mounted power transformer for the low voltage needs of the board. Do I read a 12V at one ransformer corner?

    >> Yep, 12V.

    As I see it, there two DOUBLE terminals at its top that are receiving a brown hot 230VAC input at its left terminal and then having the right terminal jump over to the ckt board to stake # 9 for getting hot AC into the board.

    The pair of terminals lower down are taking in the AC blue neutral 230VAC into the transformer primary and then using the same other terminal to its side jump over the board to
    stake # 9 for getting AC neutral to the board.

    >> Both correct.

    Now confirm for me that stake 4-5-6 wires go down into that transformer as its secondary wire connections.
    I am " reading" the green wire as being the centet tap of a TOTAL secondary winding, that is either 12VC or 24 VAC that feeds into the 4 diodes to the right of stakes 5 and 6. they then make 6 or 12 VDC power supplies with the blue E-caps. They are not exposing their voltage ratings to my view . . .but I can see the two larger ones as having 220ufd values.

    >> Yes. Green/yellow is on the middle rear (ie. bottom of the transformer coil), brown on top and orange/white on the bottom.
     
  12. budster

    budster

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    Dec 30, 2020
    Confession time, I decided just to buy the relay late last night, prior to these replies suggesting that it is probably the switch at fault. Figured for a few pounds it was worth a try.
    Better news is that I also asked the seller if he had any switches like the on/off switch here and he has kindly offered to include a basic switch (don't need the bulb), at no extra cost, when he posts out the relay.
    So, hopefully I will soon have both a replacement switch and relay.

    However, I look forward to all replies on further checking/troubleshooting that I can do.

    Thanks again.
     
  13. Bluejets

    Bluejets

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    999
    Oct 5, 2014
    As I previously said, I'm fairly certain the switch will contain 2 types of independant switches. ( as well as the neon )

    One is momentary and one is changeover. ( Google the difference, it's not rocket science)

    A "basic" switch is not going to work.

    Ed laid out a fairly detailed routine on what to check.
    If you cannot follow instructions it might be time to haul in a mate ( or a lecky) who can understand.
     
  14. Technomaniac

    Technomaniac

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    Oct 31, 2020
    If you carefully (power disconnected) and slowly, press in the armature of the relay,and watch the contacts as you do, the contacts should close BEFORE the armature hits the pole piece, closing the magnetic gap. I wondered if when the coil is energised, the contacts are not closing, but almost closing.
    Also, my best tool for polishing relay contacts is like a padded strip impregnated with diamond dust. You just insert the strip and pull it through. Works a treat. Think it came from Farnell, but not sure. Had it for years.
    Sometimes the nylon former on which the relay coil is wound, can warp a bit, and restrict the armature's movement at that last little bit, preventing complete closure of the magnetic circuit.
     
  15. Bluejets

    Bluejets

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    Oct 5, 2014
    Originally the Op pressed the armature with power on and the unit latched so I'm guessing the relay is working as it should.
     
  16. Technomaniac

    Technomaniac

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    Oct 31, 2020
    unless the armature is hitting the centre pole or distorted former before the contacts touch, and the extra pressure from manually pressing is forcing it in further than the magnetics can. Only a possibility that can be checked and eliminated.
     
  17. Bluejets

    Bluejets

    4,744
    999
    Oct 5, 2014
    As was earlier explained, if the armature hit the centre before the contacts closed, it would never have originally latched.
    AND if it were the latching contacts not closing, then the push button would have allowed initial run while the push button was held in.
    Neither is the case.
    That's the be-all-end-all of it.
     
  18. 73's de Edd

    73's de Edd

    3,081
    1,301
    Aug 21, 2015
    Sir budster . . . . .

    Your statement of . . . .
    The switch is a push-in-and-stay-in type i.e it hooks into something when you press it in and then unhooks when you press it again. Apologies again as I don't know the correct terms.

    That info nails the switch type PRECISELY, for us.


    Using the pictorial below you can see the elecro-mechanical actions of your pushbuttom main power switch.
    In an unplugged A.C. power condition use your ohmmeter in its lowest scale and touch its probes together to confirm its expected display for a shorted condition.
    Then below, you see that A-B is one pair of switch contacts and C-D are the other set.
    However, in this / your units wiring configuration , left switches VIOLET wire at B goes over and joins with the right switches D.
    In the switch OFF position no switch interconnections are being made anywhere.
    PRESS the switch to mechanically latch ON and connection should be made from B to A and D to C . . . . or since there is a violet jumper wire, all connectiionss are being joined together.

    Still in AC power unplugged condition . . . .OHM out from contacts B-A for about 10 switch on / off cycles and then from D-C, and with a measurig of 100% + response . . . I say you have one POSITIVELY WORKING switch. Both . . . . .Electrically and latching . . . . .
    Then we move on, and I will draw up the relay interface wiring and we will do a test there to see if you have " lazy leafs " syndrome.

    [​IMG]


    73's de Edd . . . . .



    A MANLY THING . . . . . . . FACTOID . . .
    It is possible for a man to use a STUD finder, without first using it on himself (zipper tab or belt buckle) and then strutting around and shouting out loudly " Found one ! "


    .
     
    Last edited: Jan 6, 2021
  19. budster

    budster

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    Dec 30, 2020
    Thanks again, I do enjoy your replies. Sorry for the slow response, been a few domestic disasters this week...

    My replies below in purple.

     
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