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    #1

    Use DC Power Supply to Test LCD TV???

    Hi all, I'm not sure what the heck is going on with a TV somebody gave to me recently. Everything *looks* fine except a couple of suspect solder joints. I was hoping that I could hook this TV up to my DC power supply to see if the rest of the TV works before wasting time working on the power supply.

    The TV is an Insignia NS32LCD. Uses 5V sleep and 24V powered on.
    The DC is named MPJA 15601 PS. It's capable of 30V and 4A.

    Any idea what this TV might draw current wise? I'm a little worried about the power-on current spike, tho it's probably reasonable.

    Would it be crazy to try this? How would I do it?

    Thank you all!
    Tags: None
    #2
    Re: Use DC Power Supply to Test LCD TV???

    Originally posted by steggie View Post
    Hi all, I'm not sure what the heck is going on with a TV somebody gave to me recently. Everything *looks* fine except a couple of suspect solder joints. I was hoping that I could hook this TV up to my DC power supply to see if the rest of the TV works before wasting time working on the power supply.

    The TV is an Insignia NS32LCD. Uses 5V sleep and 24V powered on.
    The DC is named MPJA 15601 PS. It's capable of 30V and 4A.

    Any idea what this TV might draw current wise? I'm a little worried about the power-on current spike, tho it's probably reasonable.

    Would it be crazy to try this? How would I do it?

    Thank you all!
    At one time it was acceptable to use the word 'crazy'. Now we are more sophisticated and we say 'the idea is sub-optimal'.

    Essentially you MIGHT be able to do this with linear regulators, but I doubt it. It would be much better to use two DC-DC converters. While the design would be almost a matter of copying something out of an application note, construction would be non-trivial.

    In my opinion, you would be time and money ahead to see what the problem is with the original power supply.

    PlainBill
    For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

    Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

    Comment

      #3
      Re: Use DC Power Supply to Test LCD TV???

      Also, a good 32" LCD TV is going to pull around 7-8A on the 24V rail, unless you considerably reduce backlight brightness.
      Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
      For service manual, schematic, boardview (board view), datasheet, cad - use our search.

      Comment

        #4
        Re: Use DC Power Supply to Test LCD TV???

        I was hoping to first test the standby electronics separately by powering the 5V harnesses, then try the 24V separately in the same fashion, then if both work, borrow a smaller power supply to power both at the same time. Does the 5V rail scavenge off the 24V when the TV us powered on, or is that a dedicated source for the uC's, processors and such?

        Is the 8Amps a power on current caused by the ballasts? Or a full time current? I guess ~200W sounds reasonable... scary. Maybe I can hook it up to a couple of lead acid batteries? (crazy face!)

        I took pics, would you guys like for me to post them?

        Comment

          #5
          Re: Use DC Power Supply to Test LCD TV???

          Originally posted by steggie View Post
          I was hoping to first test the standby electronics separately by powering the 5V harnesses, then try the 24V separately in the same fashion, then if both work, borrow a smaller power supply to power both at the same time. Does the 5V rail scavenge off the 24V when the TV us powered on, or is that a dedicated source for the uC's, processors and such?

          Is the 8Amps a power on current caused by the ballasts? Or a full time current? I guess ~200W sounds reasonable... scary. Maybe I can hook it up to a couple of lead acid batteries? (crazy face!)

          I took pics, would you guys like for me to post them?
          You could use some lead acid batteries, but remember the peak voltage could be 28.8V fully charged; this may damage the inverters or put them into a protection mode. Or, they may work fine - in my case I found a 12V LCD would easily run off 15V with no issues, and the inverter was directly connected to the 12V bus.
          Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
          For service manual, schematic, boardview (board view), datasheet, cad - use our search.

          Comment

            #6
            Re: Use DC Power Supply to Test LCD TV???

            Seriously, unless someone really damaged the power supply it would be easier and cheaper to repair the original supply. While they appear complex, they aren't that difficult once you start recognizing common failures (and how to find uncommon failures).

            PlainBill
            For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

            Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

            Comment

              #7
              Re: Use DC Power Supply to Test LCD TV???

              I'd suggest getting one of those adjustable laptop adapters, for example this 90w rated one:

              http://www.amazon.com/UNIVERSAL-ADAP...8338546&sr=8-1

              The description says it can do 24v @ 3.8A ... and they're cheap enough...

              For 5v I guess you could just pull the power from a computer's power supply - the red wire in hard drive power connector has 5v.

              Alternatively you could just use a linear power regulator - there are fixed cheap regulators, for example this is only about 3$:

              http://search.digikey.com/us/en/prod...1121-ND/771590

              Comment

                #8
                Re: Use DC Power Supply to Test LCD TV???

                You might try cleaning or replacing the power tactile switch and other switches on the button assembly. It worked for mine.

                Comment

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