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    Norstar NT5B01 power supply

    Hi guys! Been a little while, but it is busy here. The Title supposed to be Nortel, not Norstar... but I can't change it?
    I have a actually two Nortel NT5B01 616 phone systems. 6 lines 16 phones. Number one quit on me like 3 months ago. So we put a spare one in and that quit yesterday too in the exact same way. Now we don't have any phones. What happens with both of the phones systems that they act like there is no power. I verified fuses o.k. diodes and mosfet O.k., all electrolytic caps are good, but zero power out. There is 169V on the filter cap. I can see pulsating voltage, on the 2 optos and the driver IC, but the damn thing doesn't start. The white opto SCR is a 4N39 and that checks out. I see a diode on one side and an SCR on the other. Than there is this UC2844 PWM and another opto. There are no schematics available to my knowledge. If someone has one, I'd be interested! That is as far as I got.
    Attached Files
    Last edited by CapLeaker; 07-05-2015, 08:02 AM.

    #2
    Re: Norstar NT5B01 power supply

    replace the startup capacitors.
    dont waste time with an esr meter - they need ripple current handling in this application.
    and check for any shorted rectifier diodes.

    Comment


      #3
      Re: Norstar NT5B01 power supply

      No shorts anywhere. All diodes are good, but the mosfet isn't switching. Makes me think there is a problem with the PWM. The startup cap measures fine, but I'll replace it and try again. Thanks stj for giving me more ideas.

      Comment


        #4
        Re: Norstar NT5B01 power supply

        if the cap dont fix it, check any resistors inline wih the power to the chip/startup cap.

        we used to call them startup-resistors, they bleed rectified mains into the cap to charge it up - they sometimes changed value.

        if that's o.k. replace the 2844 i.c.

        look at page 8.
        mains goes through r2 and charges c2 and c3 until it builds enough energy to start the circuit.
        once it's running the caps are kept charged by d2 and d3.
        Attached Files

        Comment


          #5
          Re: Norstar NT5B01 power supply

          So. I just found another minute and re measured things in the starting circuit. So indeed the PWM output is dead as a door nail. The VCC on the PWM is ramping up and down from 10V up to 14V and back down to 10V endless loop. R251 (green) 75K is good. The start up cap C233 (orange) is good, C232 (blue) is good, R252 (brown) 120K is good. replaced start up cap, no change. I guess I'll have to change the PWM next.
          Last edited by CapLeaker; 07-05-2015, 03:49 PM.

          Comment


            #6
            Re: Norstar NT5B01 power supply

            or the fet has a problem wih a leaky gate?

            Comment


              #7
              Re: Norstar NT5B01 power supply

              Well, I have never thought of a leaky gate (and frankly never came across one yet either), but I took the Mosfet out and checked it with my multi meter and it was good. I have ordered a new PWM and Opto Isolator and a Mosfet (just in case). The 4N39 is nowhere to be found. I guess time will tell. I should have the parts in 2 or 3 days.

              Comment


                #8
                Re: Norstar NT5B01 power supply

                digikey lists 4n39
                this imply's a CNY30 could be used.
                http://www.isocomoptocouplers.com/CNY30.HTM

                Comment


                  #9
                  Re: Norstar NT5B01 power supply

                  I know that Digikey lists the 4n39, but none is available to buy. the CNY30 and 34 are not listed there. I think another alternate is a H11C6 but none in stock either.

                  Comment


                    #10
                    Re: Norstar NT5B01 power supply

                    Here is the fix: In my case the UC2844 PWM was the problem = dead. I also changed the CNY17F2 Opto for good measure and I am going to change the 4N39 as one leg isn't showing quite right on the SCR side, once I find one. The phone system works again
                    Last edited by CapLeaker; 07-08-2015, 07:45 AM.

                    Comment


                      #11
                      Re: Norstar NT5B01 power supply

                      Another update. A sub for the 4N39 is the MOC3010 triac and that is still available no problems.

                      Comment


                        #12
                        Re: Norstar NT5B01 power supply

                        so it's a triac? i thought the 4N series were just transistors?

                        Comment


                          #13
                          Re: Norstar NT5B01 power supply

                          the 4n39 is a opto SCR
                          the MOC3010 is a opto triac.

                          I have another Nortel NT5B01 here, that just got in. It is about 2 years newer than the first one. This one uses the MOC3010 in its place of a 4N39. Newark is referencing the 4n39 with a NTE3047. Food for thought.

                          Anyhow the phone system that just got in today, has a regulation problem. The PSU works for like 3 to 5 mins, then it turns off (the PWM stops switching). When it is working, the output voltage is not stable, maybe an opto or the voltage feedback shunt?

                          Comment


                            #14
                            Re: Norstar NT5B01 power supply

                            opto or the small cap that is usually associated with one.

                            Comment


                              #15
                              Re: Norstar NT5B01 power supply

                              Well I don't have that MOC3010 opto yet, but should be here on Monday as I have ordered some from digikey. I guess that second phone system repair has to wait now, until I get more parts.

                              Comment


                                #16
                                Re: Norstar NT5B01 power supply

                                That MOC3010 didn't cure all the problem. Changed startup cap and some other cap in the feedback circuit, tested all the rest of the electrolytic caps, diodes and resistors and I still would get random shutdowns (due to voltage spikes) although not that often anymore. I didn't physically see any cold solder joints, but once I took out the 2 inductors on the secondary and resoldered them, everything has been A1.

                                Comment


                                  #17
                                  Re: Norstar NT5B01 power supply

                                  does it use a reference like a tl431?

                                  Comment


                                    #18
                                    Re: Norstar NT5B01 power supply

                                    yes it does. Lm431. The second Norstar is a updated version of the first one. But very similar. If you look in my first post at the second picture, top left, the 2 red inductors, needed to be taken out and resoldered. Just resoldering at the bottom alone, did not fully cure the problem. I figured it finally out one I went over those inductors with my hot air soldering station, making it act up. The phone system has been running like a champ ever since.
                                    Last edited by CapLeaker; 07-13-2015, 12:56 PM.

                                    Comment


                                      #19
                                      Re: Norstar NT5B01 power supply

                                      Got another NT5B01 Norstar 6x16 phone system in today. Same thing again, no power.
                                      Opened it up, replaced the starting cap C233 (as it was out of tolerance and it had changed color a bit. Plugged it in and no go. So I measured for shorts on the output rails. One rail is 5V, the other is 19V. The 19V rail was dead short. After some tracing I found a 6KE27 TVS protection diode D64 shorted to GND. Replaced that and everything is fine.
                                      Attached Files

                                      Comment


                                        #20
                                        Re: Norstar NT5B01 power supply

                                        Well... I guess I have two more NT5B0109 6x16 (those are the DS model) with a blinking red power supply LED. Anyway, one had a bad 33uF 35V C211 starting cap. Works like a charm now.
                                        The other one had the same blinking LED symptom, but the starting cap was O.k. (I replaced it anyway). Right next to the same starting cap and between the blue long 630V 100p capacitor is a trace that blew wide open. Fixed that and replaced surface mount R319 (15R0). It had gone to 22 Ohms thus putting the PSU in a start up, shut down cycle.
                                        Not so fast. Ends up acting like one of them did before. Turns on, wait almost a minute and then shut down. Starting resistor breaking down. Grr... enough jazz for the day...

                                        Comment

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