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Thread: is my 300 mw blue labby DOA?

  1. #11
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    Quote Originally Posted by Docjohn View Post
    One thing you can do is use a ccd camera (webcam mobile phone) to look for ir. Place a white card a few inches from the output and look at the card through the camera. If you see a pink/purple glow then there is ir being emitted. If its really bright then the head may well be working but the SHG may not be functional. If you see no glow on the card try pointing the camera directly into the laser output window. This may seem daft but if there is enough ir coming out to damge the camera you would see the glow on the card. Doing this you may see some ir glow inside, if you do and its faint then the diode may well have gone to diode heaven.

    I did as you instructed. When I point the camera into the output of the laser with all lights off I can see a very faint violet-blue dot. Shall I say a prayer for a deceased IR diode?

    John


    i would say most likely! since you have opened her up already you try the same thing and see the results also try taking a picture if you can!

    but....
    can you possibly see how much power is getting to the diode itself? maybe something with the psu is wrong and it is not sending the laser enough power to lase?

    there are a lot of wires going into that diode so im not sure what wires you would even measure

    hopefully we can sort this all out though!
    -Josh

  2. #12
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    Yea, so sorry about this.
    This laser was working when I pulled it out of the projector. I have talked with DocJohn and we will get him taken care of.

    Rest asured,
    Kyle

  3. #13
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    Quote Originally Posted by stanwax View Post
    That looks like (and should be based on the system model number) a blue laser by RGB in hungary. Its likely to be 473nm DPSS rather than 44xnm from diodes.

    Dont concern yourself with the current draw from the mod input - its a control input that will show only negligable current draw - that said if it pulls an amp or 2 then you may have a prob
    What would be of greater use is to vary the mod input and observe the 5V power supply current consmuption. There will be a significant (maybe an amp) draw on this with zero volts on the mod input, as the diode will likely be biased so that it will be just below threshold at zero input. The current should increase in a reasonably linear fashion as you increase the mod input volts. The current of 4.5A may seem alot but there will be a multiwatt 808 pump diode in there so I doubt thats a crazy figure. I am concerned however that the volts are dropping to 3.2V - can your PSU supply enough current? - i would hope it can and am not trying to insult you - just important to know!

    One thing you can do is use a ccd camera (webcam mobile phone) to look for ir. Place a white card a few inches from the output and look at the card through the camera. If you see a pink/purple glow then there is ir being emitted. If its really bright then the head may well be working but the SHG may not be functional. If you see no glow on the card try pointing the camera directly into the laser output window. This may seem daft but if there is enough ir coming out to damge the camera you would see the glow on the card. Doing this you may see some ir glow inside, if you do and its faint then the diode may well have gone to diode heaven.

    As you rightly pointed out the head should get some warmth as the TECs do their job but if its getting very hot very quickly this could be a problem and explain why there is no blue output as Blue DPSS need pretty close control of temperature to work.

    Hope it helps - keep us informed and keep asking questions.

    Rob

    PS look on the edge of the driver card - it says RGB LAser Systems
    Last night I took the lid off the head. I applied all voltages. I saw a faint red glow where the 808 diode is. It was a much brighter white thru my CCD camera. There was no change in intensity of the red with changing the mod voltage from 0 to 5v. Also the current going to the diode remained at 4.5 amps. Very faint blue-purple dot seen by CCD camera when looking into the output of the laser head. My conclusion is that the 808 is putting out very little 808nm. 20 to 30 watts of 808nm should be more than a faint red glow with the top off. Its seems that the crystals are ok.

    Conclusion= the 808 laser diode is in laser heaven.

    What do you guys think?

    John

  4. #14
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    Before drawing the death conclusion it would be worth putting an ammeter across the diode connections within the head. This will give you a true(ish) reading of the current actually going to the diode - if its in the 4-4.5A range then the likelyhood is that the diode is dead. if you cant see this sort of current then you need to look at the psu as there must be something else pulling the current.
    That said, a 20-30W of diode would pull much more than 4.5A. Though if it is a 20-30W maybe 4.5A is the standby current (holding it below threshold), in which case the driver isnt ramping up as the modulation is increased.
    I would reckon maybe 10W is a more realistic value for the pump - this would account for a 3% ir to 473 conversion which is not to far off what should be expected. As a rule of thumb you can estimate about 1.2-1.3A/watt of 808 output - only a guide though.
    Also a word of warning - dont leave that lid off for long. LBO which is likeley to be the SHG crystal is hygroscopic (absorbs water - from the air) and will degrade as it absorbs. Its not a fast process but any exposure to air will affect it so minimise this exposure.

    Rob
    If you need to ask the question 'whats so good about a laser' - you won't understand the answer.
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    Stanwax Laser is a Corporate Member of Ilda

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  5. #15
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    Also a word of warning - dont leave that lid off for long. LBO which is likeley to be the SHG crystal is hygroscopic (absorbs water - from the air) and will degrade as it absorbs. Its not a fast process but any exposure to air will affect it so minimise this exposure.


    There is a bag of hydroscopic crystals in the head, and there is a rubber seal around the top of the head. Thanks for the info.
    I will check the current going to the 808nm diode. Will put the ammeter in series with + 5v lead to diode after the driver.

    John
    Last edited by Docjohn; 10-09-2008 at 06:53.

  6. #16
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    I would not break the connection to the diode - I know it sound brutal but if you have the head open just put the meter leads across the diode this will short it out and all the current will go through the meter. Breaking the connection risks static input.

    Rob
    If you need to ask the question 'whats so good about a laser' - you won't understand the answer.
    -----------------------------------------------------------------------------------------------
    Laserists do it by the nanometre.

    Stanwax Laser is a Corporate Member of Ilda

    Stanwax Laser main distributor of First Contact in UK - like us on Facebook http://www.facebook.com/FirstContactPolymerCleaner
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  7. #17
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    roger. thanks

    john

  8. #18
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    I've done a bit of work with these units , well made , decent quality, reliable.
    There's a header on the driver board for measuring the current through the diode (the voltage drop across the current sense resistor) . It's located next to the two trimpots on the nearest edge of the board in the photo on the first page of this topic. Measure the millivolts on this header and then use ohms law & the value of the resistor to work out the current flow. It is protected by a 1K resistor against the multimeter influencing the driver circuit.
    From memory the driver needs -5v , ground and +12v . The pump diode's anode is connected to the metal shell, meaning that there should be a link between the +5v supply wire , the -12v supply wire and the chassis ground.
    The 5 volt supply needs to be "floating" ( ie. not internally refrenced to ground). I think that the driver's internal circuitry that converts the 0-5v modulation from "above ground" to "below ground" needs this link to work correctly.
    B.

  9. #19
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    Quote Originally Posted by fuzcub View Post
    I've done a bit of work with these units , well made , decent quality, reliable.
    There's a header on the driver board for measuring the current through the diode (the voltage drop across the current sense resistor) . It's located next to the two trimpots on the nearest edge of the board in the photo on the first page of this topic. Measure the millivolts on this header and then use ohms law & the value of the resistor to work out the current flow. It is protected by a 1K resistor against the multimeter influencing the driver circuit.
    From memory the driver needs -5v , ground and +12v . The pump diode's anode is connected to the metal shell, meaning that there should be a link between the +5v supply wire , the -12v supply wire and the chassis ground.
    The 5 volt supply needs to be "floating" ( ie. not internally refrenced to ground). I think that the driver's internal circuitry that converts the 0-5v modulation from "above ground" to "below ground" needs this link to work correctly.
    B.
    Didn't quite follow part. I have 1 bench supply going to 5v + and 5v-, a second going to 12v + and 12v-, and a third bench supply going to mod+ and mod- at 0-5v.

    All 3 inputs are clearly marked on the PCB as to voltage and polarity. I don't have the 3 bench supplies connected in any way except as they may be thru the PCB.

    The part I don't follow is your reference to the driver needing 5v-. The first power supply is going to 5v- and 5v+ as indicated on the PCB. Do you mean that the 5v+ input on the PCB is at PCB ground potential?

    Also don't understand the 5v floating statement. Does that happen automatically thru the PCB wiring, if the proper voltages and polarities are connected to the PCB by correctly following the silk screening on the board?

    I wondered if any of the 3 bench power supplies needed to have their negative terminals tied together. I assumed that if any of that was necessary it would happen thru the PCB. Am I wrong?

    I don't have the power supply(s) from the projector they came from. The laser head and its driver were just cut out of the projector. I have to supply all 3 needed voltages. I don't know if the positive or negative side of any of the 3 voltages was tied together thru wiring separate from and external to the laser driver board.

    Could you draw a schmatic of the wiring as you are referring to it?

    Thanks, John

  10. #20
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    Im guessing he means that they need a split rail supply which would consist of 0volst (ground) with a +5v AND a -5v which would have 10 volts between them.
    I Think fr you a wiring diagram would be of use and if you do need split supplies than this is likely to be your problem

    Rob
    If you need to ask the question 'whats so good about a laser' - you won't understand the answer.
    -----------------------------------------------------------------------------------------------
    Laserists do it by the nanometre.

    Stanwax Laser is a Corporate Member of Ilda

    Stanwax Laser main distributor of First Contact in UK - like us on Facebook http://www.facebook.com/FirstContactPolymerCleaner
    www.photoniccleaning.co.uk

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