Power Supply Info

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  • #1374
    Scott Marshall

    There’s currently 2 kinds of power supplies for the K40 around. Inside they’re the exact same supply, but just to see if we’re paying attention, the K40 makers seem to like to change the connectors they solder into the PSU board.

    To simplify things, I’ve taken to calling them “White” and Green” power supplies. This must make sense, because I’ve even seen sellers using that terminology.

    The “Green” power supply is the most common, used in about 60% of the K40s currently in the wild.
    It’s name comes from the Low Voltage output connector, the rightmost connector looking at the terminal side of the supply.
    Many of these supplies have mounting provisions and the connector for a Fan, but are not so equipped. Adding one is a worthwhile and easy upgrade. The fan required is (annoyingly) a 24V 70mm model with 60mm bolt pattern. It’s mounted using standard self threading computer fan screws. A 5V fan could be used by simply connecting it to pins 2 (-) and 3 (+) of the output connector. ALL-TEK SYSTEMS has a Plug and play fan kit on our website.

    The Green connector is a 4 pin type of connector invented by Phoenix Contact back in the 1980s if I recall correctly. They are now made my many companies, but are generically known as “Phoenix connectors” – along with at least 5 other types I know of, somewhat obscuring the clarity of the definition. Phoenix makes well over a thousand style connectors.

    This type is actually a variation of a Phoenix terminal block, and offers several advantages over it’s white counterpart. It’s screw terminated, so anyone with a screwdriver can swap wires in and out, and it unplugs, allowing a power supply replacement to be ALMOST a plug in affair (but for the high voltage connection to the Laser Tube).

    MOST times the switches and control pot connect to the Green supply using a 6 pin variant of the 4 pin Low Voltage Out connector. Likewise Line voltage comes in thru a 4 pin model identical to the Low Voltage out one (Yes they are interchangeable, be careful to make sure what you plug in where)

    The 2nd most common supply based on my survey has a white rectangular Low Voltage power out connector. The connector on the PSU (the far right one) looks like 4 square pins sticking straight up with a white plastic locking tab. The tab curiously doesn’t engage anything, but seems more to discourage plugging the connector in wrong way, as the pins are off center.
    These (“WHITE”) supplies are usually equipped with “XH” style connectors for control inputs. These are arranged as 2 2 pin connections (one for each switch) and 1 3 pin connector (for the level control).

    The White Power Supply uses the exact same internals as the Green version. If you look under the PC Board.. you will see the hole to line up with the Phoenix Style Green connectors. They can be easily interchanged by someone with the proper skills.

    Th complicate things furthur than done already, the K40 folks have seen fit to use 7 pins here instead of the 6 pins found on the Green variation. They also saw fit to use totally different and meaningless nomenclature for the pin designations. The 1st connector is a 2 pin white, pin 1 is ground, and Pin 2 is Laser enable (The switch is usually labeled “Laser Switch”) Pin 1 is marked “P+” and pin 2 is marked “G” (at least THAT makes sense). Connector #2 pin 1 is Marked “K-” and it’s really Ground. Pin #2 is marked K+ and is actually the TEST input. These 2 pins connect to the Laser Test switch (Marked “Test Switch” on most K40s).
    Connector #3 is the level control, and is Marked “G, IN, 5V” – this marking makes sense and it does what it says. “G” goes the pot CCW, “IN” goes to the pot wiper, and 5″V” goes to +5V.

    The White control connectors are what’s commonly known as XH connectors (same story on the naming, but this time it’s Molex who invented them). They can be sourced thru ALL-TEK, Ebay and many hobby shops. This style connector is commonly used for charging balance connectors on RC aircraft Lithium Polymer batteries.

    Like the Large white Low Voltage Out connector, XH terminals require special crimping tools and a supply of appropriate pins.
    This makes things a little tougher on your average laser owner.
    ALL-TEK carries custom built adapters so plugging one supply into a K40 originally equipped can be a plug and play operation.

    Here’s the pinout of each. Notice that the White Supply typically uses 3 ground pins where the Green model shares 2.
    You can interconnect them or daisy chain them in any order and it will all work fine. Under the board, they are all tied to the same ground point.

    While on the Ground subject, there’s another odd thing done in the K40’s power supply connection arrangement. You’ll notice the AC Mains connection (the far left connector, ALWAYS Green (so far)) has 4 connections. The right 2 are AC power (220 or 120v), and pin 2 is earth ground, all as expected. It’s pin 1 you have to watch out for. It’s the DC return for 15000v tube power. It MUST be connected (properly!) or you will expose anything near the wire to 15kv at lethal current levels. The K40s tube power + goes straight to the tube, but the ground is connected from the tube to the Ma meter, then the Ma meter runs to Pin 1 of the mains connectior. It is indeed tied to earth (and system) ground. ALWAYS make sure it’s connected to the correct pin, and tight.

    Here’s a “cheat sheet” on the connections for each PSU.

    Green Supply

    Connector #1
    Pin #1 HIGH VOLTAGE Return (from ma meter)
    Pin #2 AC Ground – goes to Chassis Ground and Mains Ground
    Pin #3 AC IN #1
    Pin #4 AC IN #2 (In US, either can be Neutral)

    Connector #2
    Pin #1 (G) “Laser Switch”, “Test Switch”
    Pin #2 (P) “Laser Switch”
    Pin #3 (L) “Test Switch”
    Pin #4 (G) – Pot CCW Pin (turning knob ccw contacts this)
    Pin #5 (IN) – Pot Center Pin (0-5V DC output level control)
    Pin #6 (5V) – Pot CW Pin (turning knob cw contacts this)

    Connector #3
    Pin #1 24Vdc out – runs to motor controllers
    Pin #2 Ground
    Pin #3 5Vdc – Control power
    Pin #4 “L” or “LO” Laser control. This turns ON the 15KV power when pulled to ZERO volts (Negative logic)

    White Supply

    Connector #1
    Pin #1 HIGH VOLTAGE Return (from ma meter)
    Pin #2 AC Ground – goes to Chassis Ground and Mains Ground
    Pin #3 AC IN #1
    Pin #4 AC IN #2 (In US, either can be Neutral)

    Small 2 pin ‘XH’
    Connector #2

    Pin #1 (P+) – “Laser Switch”
    Pin #2 (G) – “Laser Switch”

    Small 2 pin ‘XH’
    Connector #3

    Pin #1 (K-){really Gnd} – “Test Switch”
    Pin #2 (K+) – “Test Switch”

    Small 3 pin ‘XH’
    Connector #4

    Pin #1 (G) – Pot CCW Pin (turning knob ccw contacts this)
    Pin #2 (IN) – 0-5V level control to High Voltage Power Supply
    Pin #3 (5V) – Pot CW Pin (turning knob cw contacts this)


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