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Thursday, July 27, 2017

Repairing the K40 LPS #1

Background

It is quite common for the Laser Power Supply (LPS) in your K40 to fail. Although our knowledge of the LPS design has been dramatically increased it is still unclear why certain parts of the supply fail.

I continue to collect failed LPS's dissecting each to see if we can find a reason for failure and solutions to potentially extend their life.

The bad news is that the LPS failure rate seem to be quite high. The good news is that they don't cost that much. You can get a new supply from China vendors for 60-$70. It almost seems that the LPS just like the laser tube should be considered a "consumable".

K40 LPS are high energy supplies and it is very easy to experience cascading failures when making repairs. If you consider the cost the components you could easily spend as much on a repair as a new supply!

This post is still a WIP!

Version

The stock K40 comes with LPS's in a few flavors. We have tried to categorize these supplies using the color of their connectors as a gauge. K40 LPS's typically have either all green connectors or both green and white connectors.

https://donsthings.blogspot.com/2017/01/k40-lps-configuration-and-wiring.html

Resources

We have a fairly accurate schematic and have identified most of the replaceable parts.

  • SCHEMATIC
  • PARTS LIST

Other posts regarding LPS information can be found under this search link:



Donate:

Please consider donating (button to the right of this post).
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

I also collect failed LPS in an effort to better understand them and their modes of failure. If you want to donate comment below or PM me at +don kleinschnitz 


Typical LPS failures

My research on LPS failures has revealed three common component failures: 


  • HVT, 
  • AC Bridge Rectifier, 
  • DC power supply PWM controller


I will discuss these three components and their replacement in some detail but first lets discuss safety and life threatening risks.

I do not recommend repairing your own LPS!


That said, removing and replacing components in a powered down LPS can be done successfully and safely if done correctly.



I am not guaranteeing that if you follow these procedures you will be safe.

ANY REPAIR THAT YOU DO IS AT YOUR OWN RISK AND IF YOU PROCEED PAST THIS POINT YOU ACCEPT THAT RISK AND ITS CONSEQUENCES. 

Need some proof that an operating LPS is lethal.
CHECK THESE OUT

DO NOT EVER! 

  • Power up your LPS outside of a K40.
  • Power up the K40 with the anode or -L wires disconnected
  • Access the laser compartment with the AC power plugged in.
  • Access the laser compartment without first grounding the anode with a "chicken stick"* and its procedure" with interlocks in place.

Going About a LPS Repair

I haven't found a magic way to tell what part is bad. One or more of the parts cited below can cause one or more problems by themselves or as a catastrophic failure.

Here are some scenarios I have seen:

  • Scenario 1: F1 blown => Do repair #1= replace F1, BRI
  • Scenario 2: Fuse still blown after Repair #1 => Do repair #2 = replace F1, BR1 and PWM
  • Scenario 3: Arching, low or no power without scenario 1: Do repair #3 = replace HVT

I will add more scenarios as research continues.

I will refer to this picture for these repairs

High Voltage Transformer (HVT): Replacement Procedure


  1. Test for bad HVT: position the head over a piece of mark-able material and then press the "TEST" button on the LPS.
  2. Verify Symptoms: the laser does not fire or fires at reduced power. In addition you may hear crackling noises coming from the LPS or the laser compartment
  3. Prepare the K40: as described above
  4. Remove the LPS cover screws and lift off the cover. The fan will be attached...
  5. Unplug the FAN
  6. Locate and Remove the HVT: 
    1. Some HVTs are screwed to the frame and have a 3 pin connector. On this type remove the HVT from the frame and unplug the connector. Go to step 7.
    2. Some HVT's are bolted to the PCB. In this case you have to remove the PCB to get to the nuts.
      1. Use Procedure B to remove the PCB
      2. Remove the HVT
        1. Turn the PCB over and remove the nuts holding the HVT.
        2. Replace the HVT and its nuts.
        3. Reinstall the PCB into the chassis by reversing Proceedure B
        4. Go to step 8.
  7. Replace the HVT
    1. Replace the HVT in reverse of the order you removed it.
  8. Plug in the FAN cable
  9. Replace the LPS cover
  10. Reinstall the LPS into the K40
  11. Use Procedure C to reconnect the LPS to the laser tube
  12. Use Procedure D to test the LPS


Bottom side of PCB showing alternate HVT mounting

Bridge Rectifier: Replacement Procedure

BRI: note its orientation. + of the bridge is on the right in this view
  1. Complete Procedure A: Preparing the K40 for LPS Repair
  2. Remove the PCB using Procedure B: Removing and Replacing the PCB
  3. Locate the Bridge Rectifier BR1 on the front of the PCB
  4. On the back side and using "solder wick" and a hot iron suck all the solder from the joints of BR1. Alternately you can cut BR1 out from the top side of the PCM and then pull the remaining legs out while heating. Finally suck the solder out of the joints leaving open holes for the new part.
  5. Replace BRI by inserting a new part and re-soldering its three legs. You can replace BRI with a direct replacement or substitues.
  6. IMPORTANT: Insure that the new BRI is oriented with its "+" lead to the right as this picture shows. The "+" marking is not shown on BRI in this view because its on the other side . You can see the "+" silk screened on the PCB. Just in sure that the replacements part "+" is aligned with the "+" on the PCB.
  7. Locate F1 and remove using the same soldering method as #4. 
  8. Replace F1
  9. Replace the PCB using Procedure B: Removing and Replacing the PCB
  10. Plug in the FAN cable
  11. Replace the LPS cover
  12. Reinstall the LPS into the K40
  13. Use Procedure C to reconnect the LPS to the laser tube
  14. Use Procedure D to test the LPS

COMMON  PROCEDURES

Procedure A: Preparing the K40 for LPS Repair

  • Remove the main AC power plug
  • In the laser tube compartment ground the anode of the laser using Procedure A1 below.
  • Unplug all the connections to the LPS.
  • In the laser compartment, pull (or cut if you have to) the sleeve from the anode. Remove any silicon insulation and remove the anode wire from its post. If the wire is soldered, un-solder it but be careful not to overheat the terminal in the tube as it may damage the tube.
  • In the right K40 compartment loosen or remove the LPS hold down screws. Sometimes the front screws can be removed and the rear screws loosened making replacement easier. From inside the right compartment pull the anode wire back through the laser compartment wall and into the right compartment. Be careful not to chafe or abrade the anode wire as you pull it through orifices in the cabinet. 
  • Remove the LPS from the K40 and place it on a work surface. "NEVER POWER UP THE LPS OUTSIDE OF THE K40!.

Procedure A1: Chicken Stick Procedure.

Make a discharge stick ["chicken stick"] (see photos's below):
See picture below, I think it is self explanatory. Mine is about 2ft long. You can use a dowel or PVC like mine. BTW I can sell you one for $200 ...:).
Note: I recommend PVC as wood can have high moisture content.

Ground the end of the wire opposite the taped end of the wire to bare metal on the cabinet. The terminal post on the back of your K40 is a good place after you insure that it is really grounded to the cabinet. You could replace the alligator clip on my example with a banana jack to make it more convenient.

Hold the end of the stick at the end opposite the taped wire. Put your other hand behind your back do not touch anything else with any part of your body.

DO NOT TOUCH THE DISCHARGE STICKS WIRE

Probe the bare wire end in and around the anode to discharge it before you enter the compartment.

If you see a spark just silently say "thank you Don, that woulda hurt!".



Procedure B: Removing/Replacing the LPS PCB

    1. Remove the 3x A screws from each corner of the PCB.
    2. Remove the 2x B screws that hold the power FETs to the chassis
    3. Remove the screws holding the 5V Reg and low voltage PWM controller to the chassis and associated heat syncs.
    4. Retain all screws and thermal insulator pads
    5. To replace reverse steps 1-4, insuring that you include the heat sync thermal pads under PWM and 5V reg

Procedure C: Connecting the LPS to the Laser

  1. Replace the anode wire in the same way it was connected, twist, solder or screw.
    1. If soldering use minimal heat. Some recommend using Teflon tape to hold wires that are twisted see video below.
  2. 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.
  3. Flow silicon around the anode wire connection (use the white tube that came with your K40) 
  4. 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.
  5. Add more silicon to the top of the silicon tube if needed
  6. Let dry for 24hrs before using the machine
Silicon pot-ing materials: 
  • Permatex Blue RTV Gasket Maker. Available in auto and big box hardware stores.

The videos below show connection and disconnection of the tube from its supply and can be used as reference example:

Procedure D: Testing the repaired LPS

Unfortunately there isn't a safe way to test a LPS outside of the K40, you will have to reinstall it in the K40 and test its operation by checking while actually marking. If you repaired this supply as a spare verification will have to wait :(.

"NEVER POWER UP THE LPS OUTSIDE OF THE K40!.

Enjoy and comment


Maker Don

Thursday, June 29, 2017

K40 High Voltage Transformer Autopsy #2

Background

This is a continuation of http://donsthings.blogspot.com/2017/06/k40-flyback-autopsy.html. In the previous post both myself and +Nate Caine tore down High Voltage Transformers (HVT) as part of our quest for knowledge of the details of the K40 LPS internals.
In this tear down the potting material was removed chemically in hopes that the circuit and its components could be kept in tack. The transformer was also sectioned a means of understanding its design.

Donate:

Please consider donating (button to the right of this post).
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.

The schematics for the LPS:



Removing the Potting

The potting was mostly removed using paint stripper. Caution: use gloves as this stuff is caustic.
Use gloves and eye protection this stuff is caustic
HVT submerged in glass container
The potting removal took nearly 2 weeks of repeatedly checking and refreshing the solution. The potting will come off in flakes which I washed off with each refresh. Unfortunately the stripper de-laminated the capacitors and destroyed their covering so no labels were visible. The diodes had no labels. 
It is probably worth experimenting with other chemicals that might work faster and not destroy the components coating but this worked good enough to get the information we needed.

Discovering the Circuit

The component connections were carefully observed as the potting removal proceeded. This version (and it seems there are more than one) used 2 HV diodes and 2 HV capacitors in a Voltage Doubler configuration. In this case (unlike the previous autopsy) there were no parallel diodes.

Circuit removed from the potting. Overlay showing connection of secondary.

Image result for voltage doubler
Example circuit. These components are not what is used in a K40 LPS

HVT Cross Section and Analysis

After the potting removal step the transformer was sectioned with an abrasive metal blade on a Dremel and then polished on a marble flat plate with 600 grit wet paper until the wire cross sections was visible.

Left: five section secondary. Right one section primary winding's


Primary Winding

The primary winding consists of 40 turns of 21 wire bundles.
Primary winding


Secondary Winding

The secondary winding consists of 5 sections of  +400 turns wired in series.

Primary winding connection leads


One section of secondary winding
The secondary does not have a center tap and is directly connected to the junction of the diodes and the minus leg of the lower capacitor. See voltage double'r example.

HVT Design

The HVT consists of a primary winding and a 5 section set of secondary winding's.

HVT Primary

The HVT primary has 40 turns in which each turn is a twisted set of 21 wires. The primary effective wire size indicates that the primary is designed to handle much more current than the secondary.

HVT Secondary

The secondary has 5 winding sections insulated from each other but connected in series. 

The turns wound on three different secondary sections were counted, one on the first  HVT and 2 from the second HVT. The first count = 499 and the two sections counted on the second HVT = 452 and 471 respectively. 
I don't think the difference in the counts are caused by counting errors. Its seems that the turns on each section are not the same (Rt). I did not further investigate this variance in turn counts as I do not think it will materially change the outcome of the analysis.

Turns Ratio

Using an average of the last HVT 2 sections turns count lets assume:  

  • Average turns per secondary section = 461.2
  • Number of secondary segments = 5
Total # of turns = 461.2 * 5 = 2306 total turns on the secondary

Therefore the HVT is a 40t to 2306t HVT transformer, a ratio of 1:57.65

Estimating Output Voltage

The voltage at the output can be expressed as:
Hv = Pv * Rt * Mv
where:
  • Hv is the output voltage
  • Pv is the voltage on the primary
  • Rt is the ratio of primary to secondary
  • Mv is the voltage multiplication factor
Therefore for every 100V on the primary the output = :
Hv = Pv * Rt * Mv
11,300 = 100 * 57.65 * 2

Calculating HVT Primary Voltage

The typical K40 PS output voltage is specified at 23,000V @20ma.


If we solve the above equation for Pv:
Pv = Hv/(Rt*Mv)

And use it to estimate the primary voltage at spec: 
Pv = 23000/(57.65*2)
Pv = 200 Volts

By inspection of the LPS schematic I estimate the HV buss to run at about 240-300 volts, 40 volts larger than the estimate above..

This error of 40 volts on the primary equates to about 2,306 volts on the output or 10% of the specified output. This error can easily be the result of an error in estimating the total turns across the 5 secondary sections [perhaps each secondary section has different turns] or simply differences in any given manufactures specified HV output.

Primary Current Estimates:

The specified max current output for a typical K40 supply is 20ma. In a transformer the voltage on the output is increased by the turns ratio. So to the current in the primary is larger than the current in the secondary by that same ratio (Rt). 

Therefore: 
Pi = Si * Rt
where;
Pi = the primary current
Si = the secondary current
Rt = the turns ratio

Solving for the primary current using K40 LPS specs and given the output current = .02 amps
Pi = .02 * 57.65 = 1.1 amps

Learning's

A K40 HVT contains a high current primary and a multi-section secondary. A high turns ratio secondary in combination with a voltage double'r  creates approximately 11,300 volts per 100 volts of primary voltage.
This autopsy provides a model of the HVT that more completely characterizes a key component of a K40 LPS... its HVT.

If the above analysis holds true then the following has been verified:

  • K40 LPS are easily capable of voltages in excess of 23,000 volts
  • A K40 HVT's include a voltage doubl-er in its output stage
  • A K40 HVT cannot be tested using a standard DVM because it cannot forward bias the internal HV diodes. Each HV diode is actually a serially connected stack of 20 or more diodes. Voltages that exceed 120 volts might be necessary to forward bias both the diodes in this double'r configuration.
  • K40 HVT's are not repairable

Suspicions of K40 LPS Failure Modes

I suspect that LPS failures fall into these categories:
  • AC plug swapped with the DC plug damaging the supply's enabling circuits
  • The low voltage PWM controllers output shorting, blowing itself and the bridge rectifier.
  • The Bridge rectifier failing under load. 
  • Arc's causing excessive secondary current, opening the HVT's diodes.

What's Next To Do On the K40 LPS Quest

  1. Map the actual voltages in the LPS including the primary's HV buss to further verify the above model.
  2. Scope and capture dynamic views of the internal circuitry's operation.
  3. Scope and capture dynamic views of the Lasers current and voltage while marking.
  4. Review the component specifications and verify that specifications are not being exceeded in actual operation.
  5. Noodle a safe HVT DIY HVT tester. 
  6. Noodle a safe and DIY HV tester

Enjoy and comment
Don


Saturday, June 3, 2017

K40-HVT Autopsy

Background

A more recent post on this subject.

The High Voltage  Transformer (HVT) is the business end of the K40 LPS. To date we have little knowledge of what is inside that "potted" assembly.

That is about to change as the result of the communities contributions to the HV lab and the dead HVT that  +Phillip Conroy sent to me all the way from Australia.

These two samples were first tested using test methods that I devise while trying to find a way that we could test LPS's safely and at lower voltages, with commonly available equipment.
After the tests, one of the samples was torn down with hopes of discovering what was inside the potting.
The one on the right had an autopsy. 

References to Related Posts


Donate:

Please consider donating (button to the right of this post).
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

Testing

The HVT's that +Phillip Conroy sent were tested using the simple 9V battery test and a ZVS (Zero Voltage Switching) flyback driver design that I have been tinkering with.

Battery Test

I tested both samples with the 9V Battery Test and both samples passed.

ZVS Flyback Driver

I tested both samples with the flyback tester made from ZVS driver.
One passed and one failed.

The ZDS driver uses a re purposed  SainSmart 5V~12V Zero Voltage Switching ZVS Induction Heating Power Supply Module + Coil Power Supply heating power supply module as a HV driver. The K40 fly-back's primary was connected to this drivers output and a spark gap was used for visual verification.
ZDS driver connected to a K40 HVT. Spark gap created between HV lead and grnd.


Testing Conclusions

  • As I suspected the battery test will not identify all defective HVT. Certainly, if it fails this test it is bad, however if a transformer passes this test it still may be bad..
  • One of these samples is clearly bad (no output using the ZVS driver).
  • The other is either good or the ZVS drive also cannot find all types of failures. It could be the case that the ZDS driver does not develop a high enough (voltage) drive on the primary and therefore does not stress the outputs HV section.

Fly-back Autopsy

With a known bad sample I could now proceed to try and disassemble the potted HVT module.
After removing the outer shell with a dremel saw and chisel I tried various methods:
  • Boiling (NOT)
  • Heating with heat gun (NOT)
  • Real "hacking", chipped with chisel but pieces broke off like shards taking the circuit with it
  • Dremel tool, worked but would take many days and lost of bits.
HV diodes and what look like caps exposed and sheared off with the chips.
Some Dremel work to try and expose the circuit


Toaster Oven

I heated the unit to 450F and the material would flake off, rather than chip when stabbed with a pointed. While it is hot the potting becomes a hard chalky-like consistency. With careful poking I got parts to release. Unfortunately by the time I discovered this technique some of the parts had already broken and circuitry came off  with the chips making it harder to guess the circuit. At least I have one method that works and I now know where the parts are.

Results of Tear Down #1

I learned the following from this tear down.
  1. The HVT contains more than just primary and secondary winding's.
  2. There are 2 additional component types inside the HVT and the circuit possibilities are.
Notes: 
  • The additional components are across the HV (RED) and ground (BLACK) side of the secondary.
  • The black components measured open. HV diodes measure open when tested with a DVM. 
  • Split Core (left-right halves)
  • Secondary coil (bigger)
  • Primary coil (smaller)
  • HV capacitor (blue), 2x
  • Diode assy (black), 3 pairs
  • Stud (copper). 2X

A Much Better Autopsy & Analysis

Since my attempt to spill the guts of a K40 HVT +Nate Caine expertly cross sectioned a HVT. One of two from a 80 watt machine. By inspection the single HVT from the pair looks to be the same construction as my 40W sample, except for the number of diodes in parallel.

+Nate Cain's Autopsy disclosed that the circuit that I could not identify is a HV full wave bridge made up of  4 sets of 3 diodes in parallel. Each diode is made up of 20 diodes likely to attain the roughly 20,000V the HVT requires.

One difference between the K40 and K80 transformers is the # of diodes in parallel. The K40 has 2x in parallel whereas the K80 has three.

Next Steps

Explore a chemical alternative to removing the potting so that we could potentially test the internal components of bad HVT's.
Cross section the other K40 HVT sample like +Nate Caine did.
Cross section one of the diode pairs.
I think we certainly have enough information to understand the HVT module, the last piece of the LPS puzzle. Now we need to find out why these fail so often.
Update the schematics to coincide with recent community findings.


Enjoy and comment
Maker Don

Wednesday, May 17, 2017

K40 Coolant Flow and Termperature Sensing

Background

The K40 laser needs coolant that is maintained at the correct temperature to prevent damage to the tube. It is not uncommon to forget to turn on a coolant pump or to have a pump or water system failure while running the K40. 
Sensors are easy to install in a converted K40 and the protection of the laser tuber certainly warrants the installation annoyance and cost of a flow sensor.

It is also desirable to know the temperature of the water and the tube. This post also outlines the installation of an inexpensive water temp sensor and control.

Donate

Please consider donating (button to the right of this post).
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

Flow Sensor

Sensor

The loss of cooling water will certainly cause damage to the laser and the laser power system. Every system should have a flow sensor plumbed in series with the pump and the lasers cooling jacket.
The sensor that I use is:

This sensor needs to be installed on the output side of the laser. I made a hanger to hold it upright on the side of a 5 gal bucket. This way it insures that water is flowing out of the laser and it can detect any leaks from the pumps output to the sensors input.




Electrical connections;

The flow sensor is connected in series with the interlock circuit and in effect stops the laser from firing if there is no flow. 
See Build Schematics  for full machine details

If you for some reason do not want to add a sensor at least insure that the pump comes on with the machine. You can simply plug the pump and machine into the same power strip and turn them both on at the same time.

The End of My Tube Fell Off!

If you did not install a water sensor then at some point the pump will not be on, due to failure or  simply forgetting to turn it on, and the tube will overheat.

If the tube overheats the water jacket on the end of the tube can de-laminate and fall off.

Apparently if you are careful to keep it off the optical output area of the jacket you can use EPOXY it back on. I would surmise that high temp epoxy would be best.

GLUE IT BACK ON!

Temperature Monitoring

The laser must stay within its coolant operating range if it is to operate consistently and reliably. The cooler the laser is kept the more power it will be capable of. The power capacity of the laser will change with temperature therefore it is important to monitor the water temperature and prevent the laser from operating is the temp gets to high.
Install temperature monitoring electronics such as:

This device's relay contacts (NC) is also wired in series with the interlock circuit and will disable the laser from firing if the temperature is to high or low. The probe is put into the bucket near the output or the flow sensor.
See Build Schematics  for details.

This controller can be set up to produce an audible alarm outside of its set-points. (See the manual). I mounted it on thr front of the machine but plans are to move it up to the control panel later. The unit requires 12VDC so an additional supply is needed. Before I installed the 12V supply in my conversion I used a 12V brick plugged into a power strip. 


Enjoy and comment
Maker Don

K40 Coolant Pumps

Background

Information about common water pumps and coolant flow specifications

Donate:

Please consider donating (button to the right of this post).
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

Water Pumps

From +Scott Marshall :"When all is well, the stock system should fill a 1 gallon jug about 1/2 full in 60 seconds. About 1/2 gpm or 2 Lpm. .................. the Little Giant PE-1 is a good quality replacement pump which is just right for the k40 and available worldwide."


Enjoy and comment
Maker Don

K40 Lens Specifcations, Orientation & Cleaning

Background

Some links that pertain to K40 lenses

Donate:

Please consider donating (button to the right of this post).
Your donations help fund additional research, tools and parts that I will return to the community as information.

K40 Laser Tube Specifications, Maintenance, Failure & Replacement

Background

A collection of information about laser tubes and their care.

Warning: run your laser with properly treated distilled water as a coolant.

Donate:

Please consider donating (button to the right of this post).
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

Laser tube operating conditions (Reci Laser):

  • Water cooling: using purified water; 2 to 5 liter/minute, (31GPH-80GPH)
  • Water temperature: 10-40℃, (50F - 104F)
  • The operating environment: temperature 2-40℃,(35.6F - 104F; humidity 10-60%.
  • The working current: test current is 29mA. Maximum working current is 29mA. The running current must be kept below 27mA. The life span can reach 8,000 hours if the current is kept below 25mA.
  • The ammeter must be connected to the negative electrode of laser tube.When it is working under over high current for long term, the negative pole will appear light yellow and the life span will be shortened rapidly.
  • To protect dust from going into the insulation sheath, please wrap it with plastic film.

Laser Cooling and Condensation

Laser Tube Replacement

Tube Installation depends on the tube and there are multiple ways to connect to the pins on the tube. Pick your poison.

Basic Anode Connection Termination Methods

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 or reterminaate 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)

Other Methods

The videos below for removing a laser show connection and disconnection of the tube form its supply and can be used as reference example:
  • Videos
  • Replacement Tidbits from the web:
    • "Disconnect power from unit!!
      Gently pull the existing silicone tube off the terminal post by gently twisting and pulling it along the wire itself.

      Use a soldering gun to heat the existing terminal post to gently release the existing wire connections. Then cut and clean up those wires. Also clean out the silicone tube of the old residue. Of course you need to remove the water connections and drain the tube. When installing the new tube keep the same orientation as the old tube and reconnect the water lines. Before attaching the power leads, screw down the retaining brackets and make sure the grounding wire is secured properly.

      Since you are replacing a tube, you already have a tube and terminal posts to practice on first. Make sure the wire leads are stripped at least 1/2" long, enough to be hand wrapped tightly around the protruding terminal post. The advantage of Rosin Core Solder is that it contains a built in FLUX which helps to clean and bond.

      Before the wire strand is wrapped, make sure the silicone tube covering the wires is cleaned and placed back onto the wire. Once the wire strand is wrapped around the post, quickly heat and add some solder. Let it sit for a few seconds to cool and bond. The connection will be very secure. Just push the silicone tube back over the entire connection, completely fill the tube and connection with quick drying silicone and in about 3 hours once the silicone drys, you are back in business."

Arching [needs content]

Reattaching the Water Jacket

Under shipping pressure or in the event the tube overheats the water jacket can become detached. 
Seems as if you can epoxy it back on! Check out this post.

Cleaning the laser tube water jacket

Replace all the water in reservoir with a couple of liters of vinegar and tap water... let it run for 12-24 hours replace all water with tap water only let it run for a bit... place outlet tube into a waste pan and flush adding a bit more tap water as your reservoir drains. Purge all water and replace with distilled water and some algaecide drops for aquariums. 
See: 

Laser Tube Specifications

Parallax: Laser Failure Modes and Warranty Info 



Enjoy and comment
Maker Don

Tuesday, May 9, 2017

K40 High Voltage Transformer Tests

High Voltage Transformers are Dangerous

OPENING AND EXPOSING THE INTERNALS OF THIS LASER POWER SUPPLY (LPS) IS DANGEROUS!

LIFE THREATENING VOLTAGES ARE PRESENT IN THE K40 HIGH VOLTAGE LASER POWER SUPPLY!

I do not recommend opening the LPS and trying to perform a repair. A typical LPS can cost only $70 -80 and a High Voltage Transformer (HVT) is $20-30 the difference it not usually worth exposing yourself to these voltages and identifying a dead HVT is at best uncertain.

YOU PROCEED FROM HERE AT YOUR OWN RISK!

Other related posts are:

Donate:

Please consider donating (button to the right of this post).
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

Testing a K40 Laser Power Supply High Voltage Transformer

A common failure item in a K40 is the HVT in the LPS. This transformer is what converts line voltage to up to 20,000 VDC and when applied to the laser creates ionization. This HVT has a primary, and secondary. Although not yet verified we believe it has a HV diode and ballast resistor on the secondary. These transformers are potted so the internals are not exposed.
You cannot test the secondary circuit of these transformers without a tester. This test attempts to simulate the switching circuit on the primary as a meas of detecting an open secondary.

I am also working on a more definitive DIY HVT tester but this test can be done with household items so I thought I would throw it out there.

Donate your dead LPS and HVT to a cause

I am using dead power supplies to test ways to diagnose and identify what is causing these supplies to fail. Please donate your dead LPS or HVT to this cause and help the community get to a more reliable system.

If you want to donate leave a comment.... or get to me at +Don Kleinschnitz 

Testing Procedure

Note these instructions are for the HVT that has a 3 pin connector. I will update this post later for other types. The theory of the test is the same for them all.

HVT's are difficult to test because the HV diode in the secondary has a high forward voltage. What this means is that to find out if the secondary is shorted a large voltage is needed. An ohm meter is of no use and will read an open. The primary can be tested with a DVM.

Step 1: Unplug the machine and wait 1/2 hr. 
Then with an insulated wire ground the anode of the laser tube. To ground the anode tape one end of a wooden dowel to a wire whose end it bare and connect the other end solidly to earth ground. Grip the insulating dowel with one hand and put the other behind your back gripping nothing. Touch the bare-wire end of the wire to the anode, an arc may occur. 

Step 2: Remove the LPS from the machine. 
This means that you will have to remove the large HV wire from the anode of the Laser. With all wires disconnected from the supply remove the cover of the LPS. If your HVT has a plug connecting it to the PCB, unplug it. You can leave the HVT mounted or dismount it to test it depending on the type of HVT. There are two general types of HVT one with a connector and one mounted directly to the PCB. The second type will require removal of the HVT from the PCB.
This post outlines HVTtypes: LPS Repair & Test

Step 3; Test The Primary
With an DVM set on a low ohms scale read the resistance across the black and yellow wires in the 3 pin connector. It should be nearly 0 ohms. If not ... donate it to me :)! its dead.

Step 4: Create a Spark Gap
Connect a wire to the red wire in the 3 pin connector. Tape the red HV lead to this wire. Do not electrically connect these wires together. Rather, create as small a gap as possible between these wires. This is our spark gap and will indicate if we can develop HV in the secondary.


Step 5: Wire up the primary
Connect one side of a 9V battery to the black wire in the 3 pin connector. Connect one end of a wire to the yellow pin on the 3 pin connector leave this end free.




Step 6: Test the HVT
Rapidly touch the wire that is connected to the yellow pin on the 3 pin connector to the other terminal of the 9V battery. An arc should occur across the gap you created in step 4. If it does not ... donate it to me :)! its dead. If it does arc your HVT MAY or may not be good.


About the HVT Test

The validity of this test has not been completely verified. Although this test should show if the secondary is inoperable it does not determine if the secondary can output the correct levels or quality of voltage. It also may not detect a shorted HV diode. If this test fails it is highly likely that the HVT is dead. If it does not fail it may mean that the HVT MAY be bad and MAY not :(.
To this point I do not have a bad HVT to verify this test with. If it works for you please leave a comment.

Enjoy and comment
Maker Don