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DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

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    #21
    Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

    That input on that (AQF7) board shows +12 volts and you measure 9.6 volts, I wonder if that supply is too low causing the +9 volts to the meters to be too low.
    There are 2 diodes on that board for V3 & V4, are they 9v zener diodes by chance?

    Comment


      #22
      Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

      both diodes V3 & V4 given same voltages, 7.8V to 8V

      Comment


        #23
        Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

        Originally posted by Ali101 View Post
        both diodes V3 & V4 given same voltages, 7.8V to 8V
        I know what the voltage is, But what if that voltage is TOO LOW? The diodes seem to be connected between the + and - voltage that is supplied to the meter modules so I assume they are ZENER diodes. If they are ZENER diodes what are the numbers on them. That might give you some idea of what the voltage should be.
        What ever problem you have, effects BOTH meter modules, The only thing I can see that would effect BOTH modules is the VCC for the IC'S
        Do you have a picture of the back of that AQF7 board?

        That input on that (AQF7) board shows +12 volts and you measure 9.6 volts, That white wire seems to go over to the power supply board which is also labeled +12 volts, I found another picure of the rear of this power supply board and that+12 volt line seems to come from that TO220 (N3) mounted on the black heatsink, Is it a 7812 by chance?
        Last edited by R_J; 02-15-2020, 09:09 PM.

        Comment


          #24
          Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

          What is connected to PIN number 37
          9 PC LCD Monitor
          6 LCD Flat Screen TV
          30 Desk Top Switching Power Supply
          10 Battery Charger Switching Power Supply for Power Tool
          6 18v Lithium Battery Power Boards for Tool Battery Packs
          1 XBox 360 Switching Power Supply and M Board
          25 Servo Drives 220/460 3 Phase
          6 De-soldering Station Switching Power Supply 1 Power Supply
          1 Dell Mother Board
          15 Computer Power Supply
          1 HP Printer Supply & Control Board * lighting finished it *


          These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

          1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
          2 Hem Saw Computer Stack Board

          All of these had CAPs POOF
          All of the mosfet that are taken out by bad caps

          Comment


            #25
            Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

            @R_J no that 12V line come from Main board AQF7.820.7120 ,
            enclosed both board back side pics, i hook 12V external on AQF7.820.7173 and then it transfer 9V to LCD board and LCD IC show 9V also on pin-1 & pin-26 but it still show same error on LCD and seems this issue is not related to 9V, issue might be some where else,

            @sam Pin 37 have nothing connected, look at attached pic
            Attached Files

            Comment


              #26
              Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

              So that 12 volts from the main board IS low, maybe it is effecting something else that is causing the displays not to read properly. If the caps on those 7812 regulators go bad they can oscillate causing noise in the circuit
              I don't know if this schematic would help, but I believe the main board is similar
              Attached Files
              Last edited by R_J; 02-16-2020, 11:31 AM.

              Comment


                #27
                Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

                Can you remove the solder from PIN number ( # 37 ) and make sure that it is not touching copper trace and see what happens when you do this

                ( when the solder is removed you can remove this pin from the holder when you have the ic chip out the socket but be careful when pushing on the pin not to bend it so you can put it back in if needed )

                Because here is the problem some how it is in the test mode

                When it is in the test mode it allows you check all of your segments on your display to make sure that all it of work

                I use to use these meter kits and put them together and that how you would check that everything was working when you were done with the kit

                So if nothing is hook to the test pin then more than likely it is a bad chip

                But what I find weird is that both of are doing it

                Originally posted by Data sheet

                The TEST pin potential is 5V less than V+. TEST may be used as the negative power supply connection for external CMOS logic. The TEST pin is tied to the internally generated negative logic supply (Internal Logic Ground) through a 500Ω resistor in the TC7106A. The TEST pin load should be no more than 1 mA.
                If TEST is pulled to V+ all segments plus the minus sign will be activated. Do not operate in this mode for more than several minutes with the TC7106A. With TEST = V+, the LCD segments are impressed with a DC voltage which will destroy the LCD.
                The TEST pin will sink about 10 mA when pulled to V+.

                Also this—>

                When the TEST pin on the TC7106A is pulled to V+, all segments are turned “ON.” The display reads -1888. During this mode, the LCD segments have a constant DC voltage impressed. DO NOT LEAVE THE DISPLAY IN THIS MODE FOR MORE THAN SEVERAL MINUTES! LCD displays may be destroyed if operated with DC levels for extended periods.


                Also this —>

                10.1 Decimal Point and Annunciator Drive
                The TEST pin is connected to the internally generated digital logic supply ground through a 500Ω resistor. The TEST pin may be used as the negative supply for external CMOS gate segment drivers. LCD display annunciators for decimal points, low battery indication, or function indication may be added without adding an additional supply. No more than 1mA should be supplied by the TEST pin; its potential is approximately 5V below V+ (see Figure 10-1).
                Last edited by sam_sam_sam; 02-16-2020, 12:52 PM.
                9 PC LCD Monitor
                6 LCD Flat Screen TV
                30 Desk Top Switching Power Supply
                10 Battery Charger Switching Power Supply for Power Tool
                6 18v Lithium Battery Power Boards for Tool Battery Packs
                1 XBox 360 Switching Power Supply and M Board
                25 Servo Drives 220/460 3 Phase
                6 De-soldering Station Switching Power Supply 1 Power Supply
                1 Dell Mother Board
                15 Computer Power Supply
                1 HP Printer Supply & Control Board * lighting finished it *


                These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                2 Hem Saw Computer Stack Board

                All of these had CAPs POOF
                All of the mosfet that are taken out by bad caps

                Comment


                  #28
                  Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

                  Originally posted by R_J View Post
                  So that 12 volts from the main board IS low, maybe it is effecting something else that is causing the displays not to read properly. If the caps on those 7812 regulators go bad they can oscillate causing noise in the circuit
                  You have a good point

                  Here is something that you can try remove the power in leads and hook up to a nine volt battery to the power supply in and remove the input meter leads and shorted them together and you should see 00.00 volts or amps depending on which meter module you do it on

                  If you still get all segments are on then there is a problem with volt meter ic chip

                  You can still find these ic chip at Digikey
                  Last edited by sam_sam_sam; 02-16-2020, 02:35 PM.
                  9 PC LCD Monitor
                  6 LCD Flat Screen TV
                  30 Desk Top Switching Power Supply
                  10 Battery Charger Switching Power Supply for Power Tool
                  6 18v Lithium Battery Power Boards for Tool Battery Packs
                  1 XBox 360 Switching Power Supply and M Board
                  25 Servo Drives 220/460 3 Phase
                  6 De-soldering Station Switching Power Supply 1 Power Supply
                  1 Dell Mother Board
                  15 Computer Power Supply
                  1 HP Printer Supply & Control Board * lighting finished it *


                  These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                  1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                  2 Hem Saw Computer Stack Board

                  All of these had CAPs POOF
                  All of the mosfet that are taken out by bad caps

                  Comment


                    #29
                    Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

                    Here is a page on one way to use the test pin for the decimal point

                    On the bottom of page 4

                    https://cdn.badcaps-static.com/pdfs/...456209f9a0.pdf
                    Last edited by sam_sam_sam; 02-16-2020, 04:38 PM.
                    9 PC LCD Monitor
                    6 LCD Flat Screen TV
                    30 Desk Top Switching Power Supply
                    10 Battery Charger Switching Power Supply for Power Tool
                    6 18v Lithium Battery Power Boards for Tool Battery Packs
                    1 XBox 360 Switching Power Supply and M Board
                    25 Servo Drives 220/460 3 Phase
                    6 De-soldering Station Switching Power Supply 1 Power Supply
                    1 Dell Mother Board
                    15 Computer Power Supply
                    1 HP Printer Supply & Control Board * lighting finished it *


                    These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                    1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                    2 Hem Saw Computer Stack Board

                    All of these had CAPs POOF
                    All of the mosfet that are taken out by bad caps

                    Comment


                      #30
                      Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

                      @R_J & sam, Thanks.

                      @sam let me follow your instructions one by one & get back with results,

                      Comment


                        #31
                        Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

                        Originally posted by sam_sam_sam View Post
                        Can you remove the solder from PIN number ( # 37 ) and make sure that it is not touching copper trace and see what happens when you do this
                        IC is soldered inside of display board, mean in order to remove solder of IC i have to first remove LCD from board,

                        Originally posted by sam_sam_sam View Post
                        You have a good point

                        Here is something that you can try remove the power in leads and hook up to a nine volt battery to the power supply in and remove the input meter leads and shorted them together and you should see 00.00 volts or amps depending on which meter module you do it on

                        If you still get all segments are on then there is a problem with volt meter ic chip

                        You can still find these ic chip at Digikey
                        i had given 9V external & removed main board inputs but this not works, meter not given 00.00 Volts and it show still same

                        so should i buy two new ICs and just replace them?

                        Awaiting your further professional suggestions,

                        P.S sorry for late reply, all the day i am on work and on night i have time to test your instructions & recommendations,

                        Thanks.

                        Comment


                          #32
                          Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

                          At this point I would try some new one in it and see what happens when you do this
                          9 PC LCD Monitor
                          6 LCD Flat Screen TV
                          30 Desk Top Switching Power Supply
                          10 Battery Charger Switching Power Supply for Power Tool
                          6 18v Lithium Battery Power Boards for Tool Battery Packs
                          1 XBox 360 Switching Power Supply and M Board
                          25 Servo Drives 220/460 3 Phase
                          6 De-soldering Station Switching Power Supply 1 Power Supply
                          1 Dell Mother Board
                          15 Computer Power Supply
                          1 HP Printer Supply & Control Board * lighting finished it *


                          These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                          1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                          2 Hem Saw Computer Stack Board

                          All of these had CAPs POOF
                          All of the mosfet that are taken out by bad caps

                          Comment


                            #33
                            Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

                            Noted, will buy new IC and replace,
                            shall get back with results once done,
                            Thanks.

                            Comment


                              #34
                              Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

                              Originally posted by Ali101 View Post
                              IC is soldered inside of display board, mean in order to remove solder of IC i have to first remove LCD from board,
                              Thanks.
                              Those ic's are mounted in sockets, there is no need to unsolder them, they are likely just harder to remove due to the white stuff that was on the controls. You just need to pry them up slightly from each end.
                              Attached Files
                              Last edited by R_J; 02-17-2020, 11:20 PM.

                              Comment


                                #35
                                Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

                                I still don't get how the decimal points and especially the colon is lit... I would have thought the colon should be tied to BP to ensure it never comes on. Weird.

                                I've seen a lot of bad decimal point drive, people short out the DP to reduce BOM... and then the dp breaks later on.

                                So there are smd on the other side of the board underneath the LCD?

                                But yeah these 7106's use 9V batteries frequently and will work even when the battery discharges...
                                Last edited by eccerr0r; 02-18-2020, 12:11 AM.

                                Comment


                                  #36
                                  Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

                                  I would not be surprised if there some circuits under the display

                                  If this power supply was mine I would remove the display and maybe the meter ic chip holder and see how circuit are on this board before I put a new meter ic chip in it

                                  But that is just me

                                  Originally posted by eccerr0r View Post
                                  But yeah these 7106's use 9V batteries frequently and will work even when the battery discharges...
                                  I have seen this before and some of them were setup with a circuit that when the battery voltage went below 7.00 volts it would turn on the battery symbol and then you know you should replace the battery
                                  Last edited by sam_sam_sam; 02-18-2020, 06:14 PM.
                                  9 PC LCD Monitor
                                  6 LCD Flat Screen TV
                                  30 Desk Top Switching Power Supply
                                  10 Battery Charger Switching Power Supply for Power Tool
                                  6 18v Lithium Battery Power Boards for Tool Battery Packs
                                  1 XBox 360 Switching Power Supply and M Board
                                  25 Servo Drives 220/460 3 Phase
                                  6 De-soldering Station Switching Power Supply 1 Power Supply
                                  1 Dell Mother Board
                                  15 Computer Power Supply
                                  1 HP Printer Supply & Control Board * lighting finished it *


                                  These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                                  1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                                  2 Hem Saw Computer Stack Board

                                  All of these had CAPs POOF
                                  All of the mosfet that are taken out by bad caps

                                  Comment


                                    #37
                                    Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

                                    @R_J thank for hint, really helpful
                                    @sam i had replace new Meter IC Chip on both display boards and nothing works, all same error it showing, i remove PIN number ( # 37 ) from IC and still same,
                                    i not removed LCD screen yet from board since it soldered, inside IC section is same how R_J show on Post #34 ,
                                    possible my both LCD have some problem?
                                    @eccerr0r i not remove LCD yet but my next step will be remove LCD and see if have anything backside of board,

                                    if need any further test, shall highly appreciated,
                                    Thanks.
                                    Last edited by Ali101; 02-18-2020, 07:01 PM.

                                    Comment


                                      #38
                                      Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

                                      One word of caution about removing the display make sure that all pins are free from the board before trying to remove the display or you will crack the display pins they are made of glass

                                      So take your time when doing this task

                                      If you have a Desoldiering Gun this task would be a lot easier to do

                                      One other note

                                      Try not to put to much heat on any one pin you could heat stress that pin connections ( corners are more prone to this problem ) and the pin might break a lot easier now one thing you can do if you are having a hard time removing the solder from the pins put a damp cloth on the display while you are doing this task but if go this route you will need more heat to remove the solder
                                      Last edited by sam_sam_sam; 02-18-2020, 07:58 PM.
                                      9 PC LCD Monitor
                                      6 LCD Flat Screen TV
                                      30 Desk Top Switching Power Supply
                                      10 Battery Charger Switching Power Supply for Power Tool
                                      6 18v Lithium Battery Power Boards for Tool Battery Packs
                                      1 XBox 360 Switching Power Supply and M Board
                                      25 Servo Drives 220/460 3 Phase
                                      6 De-soldering Station Switching Power Supply 1 Power Supply
                                      1 Dell Mother Board
                                      15 Computer Power Supply
                                      1 HP Printer Supply & Control Board * lighting finished it *


                                      These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                                      1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                                      2 Hem Saw Computer Stack Board

                                      All of these had CAPs POOF
                                      All of the mosfet that are taken out by bad caps

                                      Comment


                                        #39
                                        Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

                                        i have Desoldiering Gun and hot air station, shall follow your instructions while remove LCD,
                                        Thanks sam

                                        Comment


                                          #40
                                          Re: DC Power Supply (DF1730SB-5A) Programmable LCD Reading Problem

                                          I'd seriously suggest not to remove the LCD if you can avoid it; these are exceedingly fragile - though you may be forced to in this case. I also find it very strange both displays failed in the same way - indicating perhaps a serious power problem or perhaps input went way out of range and causing some strange failure in the chip... A scope would be interesting, is the BP even being toggled?

                                          Originally posted by sam_sam_sam View Post
                                          I have seen this before and some of them were setup with a circuit that when the battery voltage went below 7.00 volts it would turn on the battery symbol and then you know you should replace the battery
                                          The weird thing is that unless this thing has electronics underneath the LCD, the 7106 does not have battery condition circuitry and thus depends on external circuitry to determine battery condition. But I would suspect one should be able to determine if there's anything under the LCD without removing it?
                                          Last edited by eccerr0r; 02-18-2020, 11:11 PM.

                                          Comment

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