Thank you to the guys at HEGE supporting Badcaps [ HEGE ] [ HEGE DEX Chart ]

Announcement

Collapse
No announcement yet.

Memorex MLT3221 - No Power

Collapse
X
Collapse
 
  • Page of 11
  • Filter
  • Time
  • Show
Clear All
new posts
Previous 1 2 3 4 5 6 7 8 9 10 11 template Next
    #81
    Re: Memorex MLT3221 - No Power

    I can do that, but out of curiosity, does this board have a 5v reg? If not how is it developed?

    Comment

      #82
      Re: Memorex MLT3221 - No Power

      Can anyone tell me what R56 value should be? It's located just to the right of EC7, one of the famed failure caps.
      Last edited by johnnieboy2; 10-16-2011, 07:56 PM.

      Comment

        #83
        Re: Memorex MLT3221 - No Power

        Originally posted by johnnieboy2 View Post
        I can do that, but out of curiosity, does this board have a 5v reg? If not how is it developed?
        This is a switching mode power supply (actually two of them on one board). Regulation is accomplished by the interaction between a TL431A voltage reference, an opto-isolator, and the SMPS controller IC. In very general terms the SMPS controller pumps energy into the primary of a transformer, the secondary voltage is rectified and filtered, and the voltage reference instructs the smps controller to vary the amount of energy dumped into the primary based on the how closely the filtered voltage matches the design voltage.

        While it sounds (and is) complicated the entire arrangement can provide over 200 watts of well regulated (within 1%) power at more than 80% efficiency from a package about the size of a cigar box. By comparison, 30 years ago I workec for a company that built 200 watt linear power supplies. They were 18" x 8" x 8" and less than 33% efficient.

        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

          #84
          Re: Memorex MLT3221 - No Power

          Thanks for explaining that.

          Comment

            #85
            Re: Memorex MLT3221 - No Power

            I've ordered a set of caps for the P/S board, 16 in all...will update when installed and tested. If this doesn't do it then it's !!! And in case of failure...anyone looking for components off this thing?, Let me know.

            Comment

              #86
              Re: Memorex MLT3221 - No Power

              As you know, your 5V DC standby voltage is most likely your problem. With that being said, the problem rests on the power board. There are only a few components that make up the 5VDC. I dont have a schematic, and I'd give my left pinky toe for one, but I think the PWM might have something to do with the standby 5V. Check to see if that main chip, near the main output connector, has 13 volts on one of the pins. I can't remember what pin it was. I'm gonna try to find a thread with more info to help out.
              The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

              Comment

                #87
                Re: Memorex MLT3221 - No Power

                Your input is most appreciated. I really don't like the 'shotgun' approach I'm using but without a schematic and lack of Digital TV experience it's that or the junk pile.

                That said, what would be the conclusion if I have or don't have the 13v?
                Last edited by johnnieboy2; 10-26-2011, 06:14 AM.

                Comment

                  #88
                  Re: Memorex MLT3221 - No Power

                  Originally posted by johnnieboy2 View Post
                  Your input is most appreciated. I really don't like the 'shotgun' approach I'm using but without a schematic and lack of Digital TV experience it's that or the junk pile.

                  That said, what would be the conclusion if I have or don't have the 13v?
                  Troubleshooting the standby power supply is rather straightforward. Dgtech is suggesting you check the power supply pin for the SMPS controller. Googling the part number and datasheet should lead you to the datasheet, which will identify the proper pins. If Vcc is missing, it suggests a problem with a bleeder resistor or the rectified mains supply. If it is low and steady, it suggests a bad SMPS controller. If it is pulsing, it suggests a short on the output or a bad startup cap.

                  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

                    #89
                    Re: Memorex MLT3221 - No Power

                    All I got was some low levels of pulsating voltages, millivolt range. Definitely replacing those startup caps when I get them. Short on the output, can you elaborate, what part... another board?

                    Last edited by johnnieboy2; 10-26-2011, 01:21 PM.

                    Comment

                      #90
                      Re: Memorex MLT3221 - No Power

                      Originally posted by johnnieboy2 View Post
                      All I got was some low levels of pulsating voltages, millivolt range. Definitely replacing those startup caps when I get them. Short on the output, can you elaborate, what part... another board?
                      Wrong controller. That's the inverter controller. The SMPS controllers would be the two 8 pin ICs near oneanother on the bottom of the board.

                      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

                        #91
                        Re: Memorex MLT3221 - No Power

                        Originally posted by Dgtech View Post
                        As you know, your 5V DC standby voltage is most likely your problem. With that being said, the problem rests on the power board. There are only a few components that make up the 5VDC. I dont have a schematic, and I'd give my left pinky toe for one, but I think the PWM might have something to do with the standby 5V. Check to see if that main chip, near the main output connector, has 13 volts on one of the pins. I can't remember what pin it was. I'm gonna try to find a thread with more info to help out.
                        This is what I was referencing in my last the comments on voltages. I'm assuming your advice relates to a different IC which I cannot seem to find. Feeling like a clutz!
                        Last edited by johnnieboy2; 10-26-2011, 01:50 PM.

                        Comment

                          #92
                          Re: Memorex MLT3221 - No Power

                          If that's the pinout for IC8 then what voltave do you have on you pin 13 VCC?
                          The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

                          Comment

                            #93
                            Re: Memorex MLT3221 - No Power

                            Originally posted by johnnieboy2 View Post
                            This is what I was referencing in my last the comments on voltages. I'm assuming your advice relates to a different IC which I cannot seem to find. Feeling like a clutz!
                            Well, since you were nice enough to provide good pictures, I'll return the favor.

                            These identifications are tentative; if you supply the part number of the first three I an confirm them.

                            Blue circle - PFC Controller.

                            Yellow circles - Standby and Main SMPS controllers

                            Orange circle - Inverter controller.

                            Red circle - unknown, but possibly a 'power good' sensor.

                            PlainBill
                            Attached Files
                            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

                              #94
                              Re: Memorex MLT3221 - No Power

                              Originally posted by Dgtech View Post
                              If that's the pinout for IC8 then what voltave do you have on you pin 13 VCC?

                              .024 to .029 volts fluctuating

                              Comment

                                #95
                                Re: Memorex MLT3221 - No Power

                                Originally posted by PlainBill View Post
                                Well, since you were nice enough to provide good pictures, I'll return the favor.

                                These identifications are tentative; if you supply the part number of the first three I an confirm them.

                                Blue circle - PFC Controller.

                                Yellow circles - Standby and Main SMPS controllers

                                Orange circle - Inverter controller.

                                Red circle - unknown, but possibly a 'power good' sensor.

                                PlainBill
                                Gosh, I need a microscope! Best I can tell...

                                blue...very hard to read, guesstimate...ST (?) C2747 or CZ747
                                yellow...top one in pic is 78074 and STM4410A
                                yellow...6675A (Extremely hard to read accurately)
                                orange...SG3525AN
                                Red...D78F9222CX
                                Last edited by johnnieboy2; 10-26-2011, 09:06 PM.

                                Comment

                                  #96
                                  Re: Memorex MLT3221 - No Power

                                  I guess I was wrong to think that chip was the main PWM for this power supply. I could not find any schematic to go by. How would I identify this as the main PWM in this circuit (for furture ref.)?
                                  The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

                                  Comment

                                    #97
                                    Re: Memorex MLT3221 - No Power

                                    Originally posted by Dgtech View Post
                                    I guess I was wrong to think that chip was the main PWM for this power supply. I could not find any schematic to go by. How would I identify this as the main PWM in this circuit (for furture ref.)?
                                    Aww, crap!!! It looks like I was wrong. I'm going to have to look over this again. One of the ICs I identified as an SMPS controller is a power FET, the other isn't identifiable, both are on the cold side of the power supply. The one I thought was an inverter controller is an SMPS controller. No, it's worse than that. The SG3525AN is definitely the controller for the high voltage (inverter) output. And the SMPS controller must be on the hot side of the power supply

                                    PlainBill
                                    Last edited by PlainBill; 10-27-2011, 07:27 AM.
                                    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

                                      #98
                                      Re: Memorex MLT3221 - No Power

                                      Originally posted by johnnieboy2 View Post
                                      Gosh, I need a microscope! Best I can tell...

                                      blue...very hard to read, guesstimate...ST (?) C2747 or CZ747
                                      yellow...top one in pic is 78074 and STM4410A
                                      yellow...6675A (Extremely hard to read accurately)
                                      orange...SG3525AN
                                      Red...D78F9222CX
                                      OK, time to regroup. After looking this over carefully, I missed a LOT of clues, and misidentified the function of some components.

                                      IC2 (six pin IC up from the IC I circled in blue) is probably the SMPS controller. What is it's part number (yes, time to get a magnifying glass).

                                      The IC circled in blue is almost certainly the PFC controller; we aren't going to sweat the identification.

                                      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

                                        #99
                                        Re: Memorex MLT3221 - No Power

                                        IC2 (six pin IC up from the IC I circled in blue) is probably the SMPS controller. What is it's part number (yes, time to get a magnifying glass).

                                        number on this is...62739

                                        Comment

                                          #100
                                          Re: Memorex MLT3221 - No Power

                                          Originally posted by johnnieboy2 View Post
                                          IC2 (six pin IC up from the IC I circled in blue) is probably the SMPS controller. What is it's part number (yes, time to get a magnifying glass).

                                          number on this is...62739
                                          Nope, that crosses to a 3 pin IC. Sometime is you look at them at an angle the numbers are easier to read.

                                          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

                                          Previous 1 2 3 4 5 6 7 8 9 10 11 template Next
                                          Working...
                                          X