NiCad Battery Charger

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  • killian6pk
    Badcaps Veteran
    • Apr 2010
    • 502
    • USA
    #1

    NiCad Battery Charger

    My charger quit working and when I got the board out and did some checking the fuse was fried and I replaced that. Now I got power thru the fuse. No power after fuse. Burnt area on board led me to large axial diode. It tested bad. It is a MR 856. Found the datasheet at http://www.datasheets360.com/pdf/5519018583120582699

    Question is if I have another diode with similar amps and voltages but not an MR 856 can I use it? I have bunches of Diodes from repairing monitors and tvs just don't know if substitutes are allowed like you do with capacitors.

    Also on this board is a resistor soldered on one leg and the other leg is twisted together with a small diode. The oposite leg of the diode is soldered thru the other hole in the board. Never seen this done. Is it kosher?
    Have you ever stopped to think and then forget to start thinking again?

    As a very wise man once said on this forum: "Of all the things I have lost I miss my mind the most."
    Tags: None
    • stj
      Great Sage 齊天大聖
      • Dec 2009
      • 31085
      • Albion
      #2
      Re: NiCad Battery Charger

      you probably have more problems than the diode.
      got foto's ?

        Comment

        • SteveNielsen
          Retired Tech
          • Jun 2012
          • 2327
          • USA
          #3
          Re: NiCad Battery Charger

          Originally posted by killian6pk
          My charger quit working and when I got the board out and did some checking the fuse was fried and I replaced that. Now I got power thru the fuse. No power after fuse. Burnt area on board led me to large axial diode. It tested bad. It is a MR 856. Found the datasheet at http://www.datasheets360.com/pdf/5519018583120582699

          Question is if I have another diode with similar amps and voltages but not an MR 856 can I use it? I have bunches of Diodes from repairing monitors and tvs just don't know if substitutes are allowed like you do with capacitors.

          Also on this board is a resistor soldered on one leg and the other leg is twisted together with a small diode. The oposite leg of the diode is soldered thru the other hole in the board. Never seen this done. Is it kosher?
          A similar diode will probably work fine. The resistor/diode may have been a mod done by direction of the manufacturer after initial assembly. We used to have to do that sort of thing now and then when I worked in electronics assembly.

            Comment

            • killian6pk
              Badcaps Veteran
              • Apr 2010
              • 502
              • USA
              #4
              Re: NiCad Battery Charger

              Found a IN5406 Diode in my stock. It is a 500V Maximum Recurrent Peak Reverse Voltage,3A Max Average Forward Rectified Current, 150A Peak Forward Surge Current, which looks pretty close. Thanks for the reply. I was hoping that would be the answer.
              Have you ever stopped to think and then forget to start thinking again?

              As a very wise man once said on this forum: "Of all the things I have lost I miss my mind the most."

                Comment

                • killian6pk
                  Badcaps Veteran
                  • Apr 2010
                  • 502
                  • USA
                  #5
                  Re: NiCad Battery Charger

                  I may well have other problems. I will take some pictures and post them. I think someone has done some work on this before I got it. You can tell where someone tried to get into the case. Also there is a trace that someone has tried to repair. One leg of a large black object (my guess is it is a coil) was not even attached. Funny thing is that when I first got it, it charged the batteries. Then it stopped working guess that is when the fuse blew.
                  Have you ever stopped to think and then forget to start thinking again?

                  As a very wise man once said on this forum: "Of all the things I have lost I miss my mind the most."

                    Comment

                    • killian6pk
                      Badcaps Veteran
                      • Apr 2010
                      • 502
                      • USA
                      #6
                      Re: NiCad Battery Charger

                      Pics of Charger Board. You can see the burnt area of the board where the diode was located. The large black component with the hole in the top only had one leg soldered to the board. I replaced the fuse which was shorted, it is just visable behind the large cap.
                      Attached Files
                      Last edited by killian6pk; 07-06-2015, 10:15 PM. Reason: added info
                      Have you ever stopped to think and then forget to start thinking again?

                      As a very wise man once said on this forum: "Of all the things I have lost I miss my mind the most."

                        Comment

                        • stj
                          Great Sage 齊天大聖
                          • Dec 2009
                          • 31085
                          • Albion
                          #7
                          Re: NiCad Battery Charger

                          fuses are supposed to be shorted!

                          check if Q1 is shorted.
                          Last edited by stj; 07-06-2015, 11:57 PM.

                            Comment

                            • budm
                              Badcaps Legend
                              • Feb 2010
                              • 40746
                              • USA
                              #8
                              Re: NiCad Battery Charger

                              How about a good clear pictures of the bottom side of the board?
                              That black component with a hole in the middle is an inductor or transformer.
                              BTW, your picture is mirrored that makes it hard to read the designators.
                              Last edited by budm; 07-07-2015, 12:05 AM.
                              Never stop learning
                              Basic LCD TV and Monitor troubleshooting guides.
                              http://www.badcaps.net/forum/showthr...956#post305956

                              Voltage Regulator (LDO) testing:
                              http://www.badcaps.net/forum/showthr...999#post300999

                              Inverter testing using old CFL:
                              http://www.badcaps.net/forum/showthr...er+testing+cfl

                              Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                              http://s807.photobucket.com/user/budm/library/

                              TV Factory reset codes listing:
                              http://www.badcaps.net/forum/showthread.php?t=24809

                                Comment

                                • killian6pk
                                  Badcaps Veteran
                                  • Apr 2010
                                  • 502
                                  • USA
                                  #9
                                  Re: NiCad Battery Charger

                                  Sorry for the confusion, I was using shorted to mean burnt to a crisp. Will include a picture with the bottom of the board picture Bud wanted.
                                  Have you ever stopped to think and then forget to start thinking again?

                                  As a very wise man once said on this forum: "Of all the things I have lost I miss my mind the most."

                                    Comment

                                    • budm
                                      Badcaps Legend
                                      • Feb 2010
                                      • 40746
                                      • USA
                                      #10
                                      Re: NiCad Battery Charger

                                      Originally posted by killian6pk
                                      Sorry for the confusion, I was using shorted to mean burnt to a crisp. Will include a picture with the bottom of the board picture Bud wanted.
                                      Do you mean the rectifier is burnt to crisp?
                                      Also please up load the picture of the top side that is not mirrored.
                                      Never stop learning
                                      Basic LCD TV and Monitor troubleshooting guides.
                                      http://www.badcaps.net/forum/showthr...956#post305956

                                      Voltage Regulator (LDO) testing:
                                      http://www.badcaps.net/forum/showthr...999#post300999

                                      Inverter testing using old CFL:
                                      http://www.badcaps.net/forum/showthr...er+testing+cfl

                                      Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                      http://s807.photobucket.com/user/budm/library/

                                      TV Factory reset codes listing:
                                      http://www.badcaps.net/forum/showthread.php?t=24809

                                        Comment

                                        • killian6pk
                                          Badcaps Veteran
                                          • Apr 2010
                                          • 502
                                          • USA
                                          #11
                                          Re: NiCad Battery Charger

                                          I retook the front picture and included the back of the board and the original fuse.
                                          Attached Files
                                          Have you ever stopped to think and then forget to start thinking again?

                                          As a very wise man once said on this forum: "Of all the things I have lost I miss my mind the most."

                                            Comment

                                            • budm
                                              Badcaps Legend
                                              • Feb 2010
                                              • 40746
                                              • USA
                                              #12
                                              Re: NiCad Battery Charger

                                              OK, you use ceramic body fuse instead of the glass body fuse that is why I could not figure out why you said it burnt to crisp. For the fuse to be blackened like that you have very bad shorts circuit on the board.
                                              You already verify that the rectifier diodes on the board are all good? Q1 is good?
                                              BTW, the trace that goes to the battery terminal got hot and cooked away the green solder mask, seems to me that the battery is shorted and the power supply is try to force the current to the battery.
                                              Also that big resistor (low value) next to Q1 looks burnt.
                                              Do you also get the continuity between the two legs of that black round inductor? It should show low Ohms.
                                              Last edited by budm; 07-07-2015, 01:34 PM.
                                              Never stop learning
                                              Basic LCD TV and Monitor troubleshooting guides.
                                              http://www.badcaps.net/forum/showthr...956#post305956

                                              Voltage Regulator (LDO) testing:
                                              http://www.badcaps.net/forum/showthr...999#post300999

                                              Inverter testing using old CFL:
                                              http://www.badcaps.net/forum/showthr...er+testing+cfl

                                              Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                              http://s807.photobucket.com/user/budm/library/

                                              TV Factory reset codes listing:
                                              http://www.badcaps.net/forum/showthread.php?t=24809

                                                Comment

                                                • killian6pk
                                                  Badcaps Veteran
                                                  • Apr 2010
                                                  • 502
                                                  • USA
                                                  #13
                                                  Re: NiCad Battery Charger

                                                  Ok Bud the burnt to a crisp reference was about the original fuse. However, the diode could also be fried at the same time. I have a substitute that I think will work for the diode. The trace on the back of the board I think I have repaired. I used a cut off lead from a component to repair the trace. The picture of the front of the board is of the board as it sat on my workbench I did not change it with software if that is what you mean by mirrowed. I have two batteries, one is new the other is the original and it's case is broken so it may be shorted as you say. Once I get this charger back together I will only use the new battery to test it. Is there any reason for the Inductor/Transformer you identified in post #8 to have had one leg unsoldered from the board? I soldered it back into the board. Thanks for your help.
                                                  Have you ever stopped to think and then forget to start thinking again?

                                                  As a very wise man once said on this forum: "Of all the things I have lost I miss my mind the most."

                                                    Comment

                                                    • budm
                                                      Badcaps Legend
                                                      • Feb 2010
                                                      • 40746
                                                      • USA
                                                      #14
                                                      Re: NiCad Battery Charger

                                                      The two legs of the inductor should be there and should show continuity, that trace got hot. The inductor may have gone bad because it is part of the pulse charging circuit.
                                                      Never stop learning
                                                      Basic LCD TV and Monitor troubleshooting guides.
                                                      http://www.badcaps.net/forum/showthr...956#post305956

                                                      Voltage Regulator (LDO) testing:
                                                      http://www.badcaps.net/forum/showthr...999#post300999

                                                      Inverter testing using old CFL:
                                                      http://www.badcaps.net/forum/showthr...er+testing+cfl

                                                      Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                                      http://s807.photobucket.com/user/budm/library/

                                                      TV Factory reset codes listing:
                                                      http://www.badcaps.net/forum/showthread.php?t=24809

                                                        Comment

                                                        • killian6pk
                                                          Badcaps Veteran
                                                          • Apr 2010
                                                          • 502
                                                          • USA
                                                          #15
                                                          Re: NiCad Battery Charger

                                                          so the only test for the inductor is continuity?
                                                          Have you ever stopped to think and then forget to start thinking again?

                                                          As a very wise man once said on this forum: "Of all the things I have lost I miss my mind the most."

                                                            Comment

                                                            • budm
                                                              Badcaps Legend
                                                              • Feb 2010
                                                              • 40746
                                                              • USA
                                                              #16
                                                              Re: NiCad Battery Charger

                                                              Yes, but that will only tell us if the coil does not have open winding, it will not tell us if it has shorted turns or not.
                                                              Never stop learning
                                                              Basic LCD TV and Monitor troubleshooting guides.
                                                              http://www.badcaps.net/forum/showthr...956#post305956

                                                              Voltage Regulator (LDO) testing:
                                                              http://www.badcaps.net/forum/showthr...999#post300999

                                                              Inverter testing using old CFL:
                                                              http://www.badcaps.net/forum/showthr...er+testing+cfl

                                                              Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                                              http://s807.photobucket.com/user/budm/library/

                                                              TV Factory reset codes listing:
                                                              http://www.badcaps.net/forum/showthread.php?t=24809

                                                                Comment

                                                                • killian6pk
                                                                  Badcaps Veteran
                                                                  • Apr 2010
                                                                  • 502
                                                                  • USA
                                                                  #17
                                                                  Re: NiCad Battery Charger

                                                                  tested the inductor there is continuity. I am going to test the Power Mosfet next. It's datasheet is at https://cdn.badcaps-static.com/pdfs/...2ff9e64668.pdf The number on it is IRF644.
                                                                  Have you ever stopped to think and then forget to start thinking again?

                                                                  As a very wise man once said on this forum: "Of all the things I have lost I miss my mind the most."

                                                                    Comment

                                                                    • kc8adu
                                                                      Super Moderator
                                                                      • Nov 2003
                                                                      • 8832
                                                                      • U.S.A!
                                                                      #18
                                                                      Re: NiCad Battery Charger

                                                                      the mosfet is bad too.
                                                                      along with your batteries.all the cells short.
                                                                      black and decker/dewalt chargers like that one also have high voltages on the battery terminals.careful!

                                                                        Comment

                                                                        • orbiter
                                                                          Member
                                                                          • Mar 2011
                                                                          • 37
                                                                          • UK
                                                                          #19
                                                                          Re: NiCad Battery Charger

                                                                          You may have an open resistor there also adjacent to R36.. It looks burnt on one side?
                                                                          Don't Bin It - Repair It.

                                                                            Comment

                                                                            • Agent24
                                                                              I see dead caps
                                                                              • Oct 2007
                                                                              • 4977
                                                                              • New Zealand
                                                                              #20
                                                                              Re: NiCad Battery Charger

                                                                              Originally posted by orbiter
                                                                              You may have an open resistor there also adjacent to R36.. It looks burnt on one side?
                                                                              I reckon so too.. and it's in series with the diode which also blew so that makes sense... and which powers the MOSFET.

                                                                              It could well be that's what shorted to begin with, blowing the resistor, diode and fuse.
                                                                              "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                                                                              -David VanHorn

                                                                                Comment

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