Lambda Power Supply Problems

Discussion in 'Electronics Resources' started by T&RTech, Jan 2, 2012.

  1. T&RTech

    Thread Starter New Member

    Jan 1, 2012
    I have a LM H12-OVMYV 20V 67A Lambda Supply that has developed problems. I wonder if anyone in the forum has had any experience with this type of supply. When I put it under load, 10 to 15 amps draw, the voltage drops way down. If I put a full load on it, it will draw about 20 amps according to the amp meter on the supply but the regulated voltage which I have set to 13.8 DC drops way down. I do not seem to see any visible issues. No ripple noticed on the scope. I have not been able to find a Service Manual or schematic diagram for this supply. I have a 120 vac step up transformer I used to use to feed it the 208 volts it needs. For a number of years I have been feeding it with 120 vac without any problems and much less heat developed in the heat sick. It would only yield about 45 amps but that was more than I needed.

    Any comments on this problem or availability of a manual would be much appreciated.
  2. hgmjr

    Retired Moderator

    Jan 28, 2005
    It sounds like there may be an error in the hook up of the supply. If you take a digital picture of the terminal connections and include a sketch we can confirm that your hook up in correct. One possible explanation would be that the + and - sense terminal (if they are present on this model) are not connected correctly.

  3. jimkeith

    Well-Known Member

    Oct 26, 2011
    What is the vintage of this PS?
    Is it a linear with a SCR preregulator?
    If so, I can provide a sample schem that may be helpful.
    (LK series, 20V @ 66A)

    When I needed a schem for mine, I called them and they were most gracious and emailed it to me.
    I was then able to troubleshoot and repair very simply what previously was a piece of junk.
    Last edited: Jan 2, 2012
  4. T&RTech

    Thread Starter New Member

    Jan 1, 2012
    Thank you for the comments hgmjr. I believe it is hooked up correctly because it has been working for many years. The + and - censers are hard wired to the main output terminals. I did check to make sure that the wire was not broken. I use this supply on my test bench as a 13.8 volt regulated supply. I am thinking I am going to have to focus on the regulator curcuit but have no diagram.
  5. T&RTech

    Thread Starter New Member

    Jan 1, 2012
    Thank you for the comments jimkeith. I am guessing the vintage is mid seventies? It is a heavy 110 lb beast that seems very well built. It is a linear supply that was designed for powering computers from what I understand. I have found a manual for an LM series supply but it does not list the same model number that I have. Maybe the control circuitry is about the same. It is always a bit more time consuming not having a diagram.