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Saturday, January 28, 2017

K40 LPS Configuration and Wiring


This post captures the many K40 PS configurations that I am/have worked on.

READ THIS POST if you want to know about how to digitally control a K40 LPS: 

I need Laser Power Supply's (LPS) (dead or alive) to test:

If anyone has a LPS schematic or a blown LPS that we can use to better understand its interface please contact me at: or comment below.


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Your donations help fund additional research, tools and parts that I will return to the community as information.
For other information on the K40-S build use the  K40-S BUILD INDEX with schematics

Reverse engineering Information:

From Scott Marshall on G+:

This is the manufacturers page there's specs and such there, minimal, but some info.

Inputs P+ and K+ directly drive these optos:

Driving this PWM Controller by good old Texas Instruments

Inputs are speced at 5v, but look to work on 3,3v (show 3v logic High)

It's pretty conventional switching supply stuff from there. The Hv circuit seems to be a flyback running at about 440hz (awful low) with a tripler output.
300W 11kv nominal 4-20ma (26kv insulation breakdown)


Shown in "[approx value]" are the measurements taken from my machine as a help in troubleshooting.

These measurements are approx and your actual readings may vary.
However if they are way off that may be an indication your have a problem.

BTW: wire colors also match my machine but yours may be different.

AC Power Connector

Not always in this order
  • -L (cathode of laser) [0 ohms to frame and to cathode of laser]
  • FG (frame ground, directly connected to frame)[0 ohms to frame]
  • AC (one side of main power)*
  • AC (other side of main AC power)*
* measured AC across the mains = [whatever your mains volts is]

 DC Power Connectors:

The DC Power connector on the LPS typically contains these signals:

[* ] = measurements with DC connector disconnected
  • 5VDC (Yellow) [*5VDC to frame & gnd]
  • GND (Black) [*0 ohms to frame]
  • 24VDC (Green) [*24VDC to gnd and frame]
  • L (Pink) (the M2 Nano LO pin connects to this pin in stock K40's) [*4VDC]

DC output capacity specs:
  • 24v@ 1 amp
  • 5V @1 amp

General LPS specs for GWWG LPS from ebay:

Taken from ebay site

Understanding K40 Laser Power Supply Configurations

To effectively test, repair, replace and convert K40 LPS it is necessary to know that kind of supply you have.
This section attempts to identify and categorize the LPS I have encountered. There are two parts to identifying the LPS:
  • Physical Configuration
  • Control Schema
An example configuration might be: GGGR-A. The notation is explained below.

Power Supply Physical Configurations:

Key to my physical configuration labelling

First Letter: color of AC power connector
Second Letter: color of control connectors
Third Letter: color of DC power connector
Fourth Letter: color of Power LED

Physical Configuration GWWG

Label on back of my LPS supply, I got to it with a video borescope :)
Ebay: MYJG40 (first time I have seen one like mine for sale)

MYJG40W [S/N: 2015090481]

Mine looks like this (I think this type is out of production): 

Physical Configuration GGGR


Laser Power Supply (LPS) Control Interface Schema's

K40 LPS typically have either 1 green 6 pin connector or 3 white connectors for control (located between the AC and DC connectors. In all cases some combination of their signals perform the same basic functions of:

  • laser enable 
  • laser
  • analog power control. 
To make things more complex in some configurations the 6 Pin green connector contains different control signals than other green connectors with the same pin #'s. For that reason along with the physical configuration it is necessary to know what control schema is used.
The basic way these signals are used is shown in the sketch below.

Showing the interface equivalent circuit.

Control Schema Labels A-C

I arbitrarily labeled the two types of control interfaces "A" - "C" to simplify the documentation.

Type "A"  LPS Control Schema

This is a common K40 supply and is usually physical configuration GWWR or GWWG.
This schema uses 3 separate white connectors in the order below from left to right.

Laser Switch (enable)

  • P+ Laser Switch [**4.28VDC]
  • P- gnd return for Laser Switch [0 ohms to frame]

Test Switch ("FIRE")

  • K+: Test switch [**4.28 VDC]
  • K-: gnd return for laser [0 ohms to frame]

    Current regulation

    • Ground: signal ground [0V to frame]
    • IN: laser current control 0-5VDC [**not sure, likely floating]***
    • 5VDC: 5V power [** 5.02 VDC]
    Note: the "Current Regulation" pot is connected across these three signals with the center tap connected to IN.
    *** you can partially test "IN" by measuring the resistance across IN to gnd while turning the Current Regulation POT on the panel. The resistance should vary with pot position.

    ** voltage measured with connectors removed

    Type "B" LPS control interface

    These supplies often have black cases and sometimes have only the control and AC connectors. They usually do not provide DC power.

    Terminal Definition as follows:

    THInput SignalOn-Off laser control,TH≥3V, emitting laser; TL≤0.3V, no laser.
    TLInput SignalOn-Off laser control,TH≥3V, no laser; TL≤0.3V, emitting laser
    WPInput SignalOn-Off laser control,TH≥3V, no laser; TL≤0.3V, emitting laser
    GGNDThis foot must be connected well with the laser machine shell and the ground of control board.
    INInput SignalThe control of laser power: Both 0-5V analog signal and 5V PWM signal can control the laser power.
    5VOutput PowerOutput 5V, the maximum output current is 20mA.

    Note: WP = water protection, this is an interlock loop for the water pump.

    Type "C" LPS Control Interface

    I think this is the configuration that ships with newer K40's.

    Type D Control Schema

     Same schema as a Type A but a "D" signal replaces the "P" and works the same.

    Special LPS Wiring

    Special wiring for this supply, note part # at top of drawing

    Converting From One Supply Type to Another

    Conversion of GGGG-C to GWWR-D

    LPS Related Album

    Enjoy and comment
    Maker Don


    1. Have a question on the current limiter for the 5V in. If you are still doing this stuff, could you drop me a line? I don't normally use this forum.

      Dave V at

    2. I am replacing Power supply in K40 - using same control board that came with unit
      old supply has D+ D- with a jumper
      I see D+ D- is mapped to Laser switch
      would I just jump the laser switch?
      totally out of my comfort zone have no one I know thats any help
      any direction you can give me much appreciated

    3. To replace the power supply digital GWWR with analog power supply it is only necessary to invert k- with k+ and G with P from the above scheme . Tested and working on laser 40w .

    4. Hi, you explained all this great. I'm a new laser user so I'm not sure I've found a way to upgrade a new power supply? I currently have a MYJG40W which is not ok and I ordered a new CLOUDRAY HY-T50. How now to connect type c to type b, please can you draw how to connect?

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