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D48-D0 flickering/flashing at a very constant rate

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    #1

    D48-D0 flickering/flashing at a very constant rate

    I have a D48-D0 that works on all counts except the backlights flash at a constant frequency of about 3-4 times a second. I used the Voltage measurements as seen in this thread (https://www.badcaps.net/forum/troubl...ure-new-boards) to compare mine.

    With CN301 unplugged with set on I have about 90VDC
    With CN301 plugged in of course the V varies based on the flickering

    These pins have 1.86 VDC not the 3.3 as shown here:
    CN201: PWM5: Pin 14: 3.3VDC
    CN201: PWM4: Pin 13: 3.3VDC
    CN201: PWM3: Pin 12: 3.3VDC
    CN201: PWM2: Pin 11: 3.3VDC
    CN201: PWM1: Pin 10: 3.3VDC

    I took each of the high V leads out of CN301 one at a time and the flickering never stopped. I think the problem is likely on the power supply. Another indication is a slight burn mark on the corner of the board. When I turn the board over I find what looks like Q303. I haven't done a lot of board level work since I was in the Navy 30 years ago. Can anyone tell me what Q303 is? I can't find the schematic for this PS online anywhere for a reference. Any pro's in here who have fixed this before?

    These power supplies are $16 plus shipping on Shop Jimmy. Just shotgun the PS?
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    #2
    If you have to have parts shipped to you, then may as well just get a whole replacement board, see if that one is a match for you: https://www.ebay.com/itm/38460069767...Bk9SR-zboviJYw

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      #3
      This is the one! Thanks nomoresony

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        #4
        Glad to help.

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          #5
          Got new part - did nothing to change the problem. I hate throwing money at this stuff. I could do the main board next but with my luck it will be fine too. I've seen "fixes" on YouTube for this before that suggest settings are going to do the trick. I am very leery of that kind of "repair"

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            #6
            With the new board, what voltages do you get on CN201, pins 7 and 8, if you can check them in standby, and when you hit power button, what are the voltages and do they change/toggle when you go from standby to power up? and make sure all your connectors are in place.

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              #7
              Pins 7&8 are zero Volts at off/standby

              Pin 7 = 3.25 VDC on
              Pin 8 = 3.3 VDC on

              Checking all the connectors here in a few after this next meeting

              Comment

                #8
                Originally posted by bscottjohnston View Post
                Pins 7&8 are zero Volts at off/standby

                Pin 7 = 3.25 VDC on
                Pin 8 = 3.3 VDC on

                Checking all the connectors here in a few after this next meeting
                Ok, that is good.

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