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Seeking help with 12v dc motor controller on golf buggy

Discussion in 'Troubleshooting and Repair' started by onedog, Nov 11, 2019.

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  1. Tha fios agaibh

    Tha fios agaibh

    2,083
    694
    Aug 11, 2014
    Screenshot_2019-11-20-11-08-17-1.png
     
    onedog likes this.
  2. onedog

    onedog

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    Oct 4, 2016
    I will probably practice first but the relay's pins mostly have a little bit of space around them so maybe not too hard. The tough one might be replacing Q3 where the pins are very close together.
     
  3. Tha fios agaibh

    Tha fios agaibh

    2,083
    694
    Aug 11, 2014
    Actually the opposite. Desoldering close pins of Q3 is easier because you can heat all three at once. The relay will be harder unless you are able to remove most of the solder.

    I recommend using a braided desoldering wick.
     
  4. onedog

    onedog

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    Oct 4, 2016
    I guess I was thinking more about soldering the replacement part.
     
  5. 73's de Edd

    73's de Edd

    2,794
    1,171
    Aug 21, 2015
    " BUBBA's " . . . no FRILLS (nor fanceeeeee equipment) procedure for the pulling of Q1 and Q2 . . .TO-220 cased power transistors .

    HOWTODOITTOIT . . . . .

    You need a piece of wood to "whittle" / shave / sand down to slightly less than the gap now existing between the transistors 3 flat terminal BCE leads
    and the adjoining PCB surface.
    The wood choice could be a large diameter bamboo skewer, chopstick or wooden clothespin half, with its cojoining central coil spring removed.
    Prep the thickness dimension of the wooden "tool" and test fit / slip in between the PCB and as close as the bent leads of the power transistor leads as is possible. You have clearance ?
    Note that when you then rotate the "stick" / tool, that in one direction of rotation, that it would cause a lifting action of the three terminals, being exerted at about the width of the stick AWAY from the lead bends, THAT would be the WRONG direction, in which to rotate.
    The other direction of stick rotation, should cause a lifting / levering action of the 3 leads, being created, right at the bend in their terminals.
    Needless to say, that is the correct direction of rotation to be used.
    Then you get your 50-75 watt soldering iron with a preference of a conical tip, then get it all tinned up to the extent that it looks like 1/4 inch length of chrome plating being on its very tip end.
    THEN you place the wooden tool into position and have the PCB positioned such that the solder joints are being on topside.
    Rehearse in your mind, the direction that the wooden tool will then be needed to rotate for the lift up action, being created close to the 3 lead bends.
    Now you need to defeat ?X? years of surfactal PbO2 and SnO2 build up on the 3 solder surfaces of the transistors BCE solder blob connections .
    Its preferrrable to initially add an application of liquid rosin flux to those blobs and then use rosin cored 60Pb / 40Sn wire solder added to the first solder blob, as the pre heated and tinned iron approachs to heat the junction of the wire solder and blob. As that first blob liquifies, shift to the side for the second one to have wire solder added to it do so also and then the same action for the final third one.
    Then you tilt the tip so that all three solder joints can be heated as you move the tip between the initial three joints, where there should just NOW be one big oval blob between the cojoined three .
    You may just barely be able to see that condition, as the tensioning on the wooden tool has levered out the transistor, free from the board, just at the minimal degree of heat presence that would free the transistor from its solder blobs.
    The REASON for the use of an insulative " tool " was keep the joints free from the heat sapping transfer, that a metal mini screw driver tip or any other metal tool that would thermally conduct away and steal heat from the joints.
    That transistor pops free at the MINIMAL heating level needed to be applied to the boards joints.

    ( I have also saber sawed and ground some one oz FR fiberglass blanks to a 1/4 wide and 2 in length with a 2 in length 1/4 in right angle bend on one end. . . . it looks like a micro carpenters square. )
    I carry 3 of these in my tool box, with 4 around, on the work bench. . . . . all still usable after 40+ years of shared use.

    Thaaaaaaassssit . . . . .

    Need to know the equivalent applicable procedure for pulling that relay ? . . . . as that will be the hardest . . . . Just ask . . . .

    73's de Edd . . . . .

    My uncle is an incredible self made millionaire. He's the guy who designed the diagram to show you which way to put the batteries in something.


    .
     
    Last edited: Nov 21, 2019
    darren adcock likes this.
  6. onedog

    onedog

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    Oct 4, 2016
    I sure would, and thanks for the offer.

    Please excuse the time delays between my posts. Apart from normal living, every time I come across something new I side-track and try to learn - and there's one helluva lot of "something new" for this old dog. For example,:
    How do you guys know what Q1 and Q2 are (BJT, FET, MOSFET)?
    With the 'front' view up and the tab furthest away from you, are the pins numbered 1,2,3 from left to right?
    Is the material between the tabs and the heat sink meant to be electrically non-conductive and thermally conductive?
    Inter-pin "in circuit" readings for both Q1 and (with very minor variation) Q2 are:
    Pins....Diode.....Ω
    1-2.....0.003.....5.3
    2-1....0.003.....5.3
    1-3.......0.........0.5
    3-1......0.........0.5
    2-3....0.003....5.0
    3-2....0.003....5.0
    Does this tell us anything about the condition of Q1 and Q2? Do I need to replace Q1 and Q2?

    I'm super grateful for the time and expertise you guys provide.
     
    Last edited: Nov 22, 2019
  7. Tha fios agaibh

    Tha fios agaibh

    2,083
    694
    Aug 11, 2014
    Only way to know what it is for sure is to search for the part number.
    With flat side of metal tab lying down flat, 1 is on left and 3 on right.
    Usually 1 is gate, 2 collector, 3 emitter.
    For a mosfet 1 gate, 2drain, 3 source.
    Read data sheet to be certain.

    Your readings look like a shorted collector- emitter, provided you tested it out of circuit.
    You don't want false readings through other components.

    Primary role of thermal paste is for thermal transfer, but i'm sure some are conductive too. Especially given the fact that the metal tab can be used instead of pin 2 collector/drain.
     
    Last edited: Nov 26, 2019
  8. onedog

    onedog

    22
    0
    Oct 4, 2016
    Hi guys.
    I have removed the two obviously bad parts (RL1 and Q3).

    I have also removed the two components that look like mosfets - thanks to EDD for the removal tips. I hope to be able to test these before trying to re-assemble the beast but I'm having trouble identifying them.

    The markings are difficult to read but there appears to be 3 rows of markings. The first row has a logo and 30S233 or 305233.
    The 2nd row reads "MOROCCO".
    The 3rd row reads :"P50NE1".
    There is a possible zero below that (at the lower left corner of the case.

    Any help to identify these will be appreciated.
     
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