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Thread: CNI OEM PSU replacement

  1. #1
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    Default CNI OEM PSU replacement

    Hi!

    I have a 635nm 1W laser with a TTL CNI OEM PSU, which I want to replace with an Analog CNI PSU from a dead green which I have here.
    To do this without demolishing the red I need to set the max diode current equal to the diode current setting on the TTL psu. This is easy: I measure the voltage across the shunt resistor.

    But how about the LD TEC? Can I just measure the voltage across the TEC?
    What are the LD TEC pins on the DB9 connector?

    Thanks!

  2. #2
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    Default

    Quote Originally Posted by SideFX View Post
    But how about the LD TEC? Can I just measure the voltage across the TEC?
    What are the LD TEC pins on the DB9 connector?

    Thanks!

    You are going to need to use the ntc thermistor inside the head as well to keep the tec regulating the temperature.
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  3. #3
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    Quote Originally Posted by dave View Post
    You are going to need to use the ntc thermistor inside the head as well to keep the tec regulating the temperature.
    Hi dave,
    thank you for your response.

    So there is an ntc in the red head.. measuring just the voltage on the TEC won't do me much good then as it changes accordingly to its feedback from the NTC.
    I presume the 'new' analog PSU knows how to deal with this as it i basically the same PSU as the original TTL PSU.. right?

    But how do I adjust the TEC setpoint so it is equal to the original TTL PSU? Should I measure temperature instead? No chance I blow up the TEC because it is driven at a too high voltage or anything?

    Thanks!

  4. #4
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    Quote Originally Posted by SideFX View Post
    Hi dave,
    thank you for your response.

    So there is an ntc in the red head.. measuring just the voltage on the TEC won't do me much good then as it changes accordingly to its feedback from the NTC.
    I presume the 'new' analog PSU knows how to deal with this as it i basically the same PSU as the original TTL PSU.. right?

    But how do I adjust the TEC setpoint so it is equal to the original TTL PSU? Should I measure temperature instead? No chance I blow up the TEC because it is driven at a too high voltage or anything?

    Thanks!
    Measure the temperature the 635 TEC is operating at or the temp it is keeping the diode at and then transfer this temperature reading to the TEC temp settings of the replacement 532 PSU.
    If you can swap over the Thermistors then that will erradicate any further possible errors - And maybe even swap the TEC's????
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  5. #5
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    Quote Originally Posted by smogthemog View Post
    Measure the temperature the 635 TEC is operating at or the temp it is keeping the diode at and then transfer this temperature reading to the TEC temp settings of the replacement 532 PSU.
    If you can swap over the Thermistors then that will erradicate any further possible errors - And maybe even swap the TEC's????
    Hmm.. I'm afraid i'll demolish the head for sure if I take it apart to swap the TEC and the thermistor
    I try this scenario:
    - With the 532 head attached I turn back the LD threshold and max current to zero, so the LD stays off.
    - I measure the temperature at which the TEC keeps the 635 LD, and measure the LD current.
    - I connect the 635 head to the 532 PSU and while the LD is off I set the TEC temp to the previous measured value.
    - the I slowly increase the LD current to a maximum of that of the TTL supply, keeping an eye on the TEC temp


    Sounds ok right?

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