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Wednesday, January 4, 2017

K40 LPS repair and test

K40 LPS parts and repair

DON"T IGNORE THIS!

WARNING: LASERS AND THEIR HIGH VOLTAGE SUPPLIES ARE BOTH ELECTRICALLY LETHAL AND OPTICALLY DANGEROUS. THEY HAVE THE POTENTIAL TO KILL AND/OR BLIND YOU
  1. STAY FAR AWAY FROM THE HIGH VOLTAGE SUPPLY'S OUTPUT!
  2. WEAR PROTECTIVE EYE-WARE AT ALL TIMES WHEN OPERATING A K40!
  3. DO NOT OPERATE A K40 WITHOUT THE PROPER LASER INHIBITING INTERLOCKS INSTALLED AND OPERATING PROPERLY!
  4. USE THE CORRECT HIGH VOLTAGE SAFETY PROCEDURES

BY READING THIS POST YOU AGREE TO USE THIS INFORMATION AT YOUR OWN RISK!


Most people are not skilled enough to be around and inside a high voltage power supply

 I DO NOT RECOMMEND THAT YOU REPAIR YOUR OWN LPS. YOU PROCEED FROM HERE AT YOUR OWN RISK!


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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 schematic

Safety references

READ THIS FIRST

Replacing LPS as a Unit:

Replacing the LPS is dangerous so adhere to all HV safety precautions in this post.

Unplug your laser from the mains power and let it sit for 1 hr.

Observe how the anode wire is connected to the tube including the wire routing and restraints.
Install the new anode wire in exactly the same way.

At the Anode end of the laser tube
  • Remove the silicon sheath from the anode connection. Minimize forces on the anode pin. It should pull off but if not you may have to cut it off.
  • Your anode wire may be twisted, screwed or soldered on the anode pin.
  • Remove the old anode wire. 
  • Replace the anode wire in the same way it was connected, twist, solder or screw.
    • If soldering use minimal heat. Some recommend using Teflon tape to hold wires that are twisted see video below.
  • Route and restrain the wire in the same way. Usually tie wraps around the tube moving away from the anode end toward the cathode end.
  • Flow silicon around the anode wire connection (use the white tube that came with your K40) 
  • Push the silicon tube over the wet silicon filling the tube. If you had to cut off the tube you will need to replace it with a peice of silicon tubing.
  • Add more silicon to the top of the silicon tube if needed
  • Let dry for 24hrs before using the machine
Alternate silicon: Permatex Blue RTV Gasket Maker. Available in auto and big box hardware stores.
703 adhesive silicone rubber insulation/potting/electronic waterproof sealant (the stuff that comes with the machine)

The videos below for removing a laser show connection and disconnection of the tube form its supply and can be used as reference example:

Replacing the Current Meter & Pot 

Current Meter

This analog meters face is larger and has a larger mounting hole than stock: 
There are many choices of cheap digital mil-lamp meters that could also be used in place of the analog one. Realize however, that it is harder to visualize fast moving current changes on a digital meter than an analog one. These meters also require a separate DC power source.
Another reason that I like the analog over digital approach is that although probably overly cautious, I do not like the tube and its power supply connected in any way (dc power) into the same system as the controller. 

Current Pot

LPS Repair

As I learn more about the K40 LPS and learn how to repair them this post will collect information on how I repair and test.

THIS IS NOT A RECOMMENDATION FOR YOU TO REPAIR YOUR LPS AND YOU DO SO AT YOUR OWN RISK!

Testing Laser Power Supplies (LPS)

Coming soon

Schematic:

Thanks to +Paul DeGroot for this schematic.


Note: we know that there are uncorrected errors on the digital input side of the supply schematic, For details on the digital interface go to:

Frequently failed parts

  • Fly-back transformer*: Fly-back transformer choices are very confusing. There is a model A and and a model B type and they are different in how they connect to the PCB. There are two ways to connect to the PCB, with two bolts and with a 3 wire connector.When ordering from AliExpress you have to specify the right model so be careful.
*It has been suggested that the flyback is the only difference between a 40W and 50W power supply. I have also noticed that higher power laser power supplies use multiple flybacks to achieve their voltage.

Enjoy be safe and comment
Maker Don