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REILs HV PSU runway end identifier lights repair

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    REILs HV PSU runway end identifier lights repair

    Today I've got a REIL's (Runway End Identifier Lights) PSU on the menu. This thing is old, I mean mid '80s vintage! The PSU blows fuses. It's wired for 220V, goes to a step up transformer (~2000V) then through a rectifier and so on.

    Here is my trouble with it: The 4 individual rectifier diodes are all over the place. One has a voltage drop of 0.7V others have 1.2V some have drop of 2.8V! I checked this on another bad unit... same thing there. Some one else had a crack at it and put a normal chassis mount bridge rectifier in there, that went poof.

    My question is: Why would a XP541 (can't find nothing about this diode) that has a 0.7V drop go to anywhere between it and up to 2.8V? A 2.8v drop can't be good. Wouldn't that put an imbalance? Plus I have to find a replacement for these diodes.
    Attached Files

    #2
    Re: REILs HV PSU runway end identifier lights repair

    I do not know if this will help you out or not

    https://cdn.badcaps-static.com/pdfs/...3d66b65121.pdf

    2000 volts @ 375 amp ( maybe a rectifier diode but does not state this in the data sheet )

    It is extremely difficult to find a rectifier diodes that have these specifications that are called for in the pdf that you posted
    Last edited by sam_sam_sam; 07-08-2022, 02:50 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


      #3
      Re: REILs HV PSU runway end identifier lights repair

      Yeah, I have nominal 2000vdc laying on that voltage rail. So I would like something beefier than a 2000v diode. I am thinking the xp541 means something like 5000V 4A, or 4000v 5A. I did lurk around the common suppliers, but haven’t come up with anything. I found a manual for this thing too and scanned it. Damn… I hate it when I can repair something, but can’t because of parts issues.

      The thing that really strikes me dumb is why would a diode go excessive high on the voltage drop and what the result of the actual rectified voltage is.

      Anyone got a 2000VDC power supply laying around?

      Comment


        #4
        Re: REILs HV PSU runway end identifier lights repair

        You could be right about the 5000 volts at maybe 4 to 5 amps diodes stud mount
        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


          #5
          Re: REILs HV PSU runway end identifier lights repair

          Originally posted by sam_sam_sam View Post
          You could be right about the 5000 volts at maybe 4 to 5 amps diodes stud mount
          Look at pic #1. Diode markings are xp541. They are through hole.

          Comment


            #6
            Re: REILs HV PSU runway end identifier lights repair

            Which fuse does it blow? the F1.5A? The circuit with the XP541 diodes is protected by a circuit breaker, does it blow as well?
            Last edited by R_J; 07-08-2022, 07:16 PM.

            Comment


              #7
              Re: REILs HV PSU runway end identifier lights repair

              Rectifier diodes max. is about 1,000V for a single die, so for higher PIV voltages you have to stack them.
              So I would expect about 0.7V per diode per rated kV. If you get different # diodes then some must have failed short inside the stack. One has gold leads, the other three do not. They're pretty old and the logo on one I don't recognize. You can also test in the forward direction with current, say 10V 100mA light bulb to accurately measure Vf is it's 0.7 V or 2.8V etc. edit: the higher Vf is actually likely to be the better part. It should not be so low 0.7V
              Need at least 5kV diodes and hard to guess the average current. At least 1-2A? and I estimate max. 100A surge rating for the 1/2 cycle. It depends on the transformer secondary resistance which I don't know. That R5 15R 5W resistor does not help much as the strobe tube crowbars things until it is finished the glow.

              To troubleshoot temporarily, I would put in microwave oven rectifier diodes CL01 or HV03 is only 350mA, 30A surge but you could use for testing in case the problem is something else breaking down with the high voltage and overloading the bridge rectifier.

              Or makeup a series string of using 5-6 of 1,000PIV diodes for each one. There is lots of room, I've done this before. It would be a 1-2 inches long.
              UF5408 3A 150A surge or SF5408 3A 100A are super tough and surely more than the original diodes as far as current rating.
              SMT string of SMC US3M 1,000V 3A 120A surge, with no flux mess, ~40mm. BYT56M 1,000V 3A 80A surge.

              Number one is to make sure the bleeder resistor string is not open circuit. Be extra careful around the big caps C8 30uF 2,500V and and C9 1uF 1,000VDC, make sure no stray charge. I'd use a many 10'k ohm wirewound resistor and screwdriver. And a variac to power it.

              Can't find any other HV 1-3A rectifier diodes out there. http://www.hvgtsemi.com/newsv_457.html
              Last edited by redwire; 07-08-2022, 11:39 PM.

              Comment


                #8
                Re: REILs HV PSU runway end identifier lights repair

                I didn't bring that PSU home, it's still at work. I see that someone added a 0.1uf 1000V cap (pic 2, orange cap) across the 240Vac input legs. That wasn't originally there in the schematic and someone added that in. If it is short, it would blow the fuses too.

                Interesting idea on taking like 5 x 1000V diodes in series. I guess the room would be there. For testing purposes that idea would be good enough for Canada.

                As for the original XP541 diodes: I measured a few of them also in some other units and they really have a voltage drop between 0.7V and up to 2.8V. Interesting observation I made that made that these 2 diodes that are on the negative end where always the ones that have the 2.8V drop. The 2 diodes on the positive side are always the ones that have the least forward voltage drop for some reason. One unit has a different diode in there that is way smaller and got a voltage drop of 0.5V. Have no idea what it is, as I have to take it out first.
                That's what I thought that XP541 means something like 5000V, 4A. Keep them ideas coming as I really don't enjoy getting fried. I may wire that thing for 120Vac and hook it to my variac, but first I wanna make sure it won't blow anything.

                Comment


                  #9
                  Re: REILs HV PSU runway end identifier lights repair

                  I going to follow this post this is interesting what you are trying to fix keep us informed with your progress and if you are able to fix it
                  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


                    #10
                    Re: REILs HV PSU runway end identifier lights repair

                    A big issue with these kinds of things is any EMI can take out the radio systems which is very bad. So the added cap is to stop mains noise a little bit. Xenon strobe tube is pretty noisy like an arc inside when it's lit so this (in a modern world) would have extra EMI filtering or else you get radio glitches everytime it flashes.

                    Another capacitor not in the schematic is across the HV secondary winding, at the bridge input. Disc cap 0.005uF 3kV I think to help with spikes from the transformer or diode switching spikes.
                    The HV XP541 diodes look to be made by Semitronics Corp. as a module but no data anywhere even in avionics/military database.

                    The diode's forward voltage should not be 4:1 variation, unless it's side effects from in-circuit readings I say some are shorted/damaged inside. A multimeter diode test is not much at 1mA. 0.7V is a single die and no way that's good to 5kV. I'd pass 100mA through them then measure Vf, just a car light bulb load. You'd have to hi-pot test them at say a few kV reverse to see if they breakdown or what. I think they should blow up though if they are breaking down- C8 would dump back into them and blammo!
                    I'd use a variac. Relay K1 needs to click off though or R9/R28 will burn up.

                    It's said the strobe tube enclosure gets water in it, not sure about the HV trigger transformer where that is, must be close to the tube, the SCR drives it. Just to check if an overload exists there, on site if you find no problem.

                    Comment


                      #11
                      Re: REILs HV PSU runway end identifier lights repair

                      Unfortunately I don’t have anything much for 2kV test equipment. I think I will unhook the transformers and test anything that could do a short and figure out what’s going on.
                      I did some more lurking around the web for parts. Some parts I have found at work, but the important stuff that I really like to change, not. And those I also couldn’t find to order, like the HV diodes. I am sure that there is something wrong with them it just can’t be that the same diodes half of them reading low and the other half high in voltage drop.

                      Comment


                        #12
                        Re: REILs HV PSU runway end identifier lights repair

                        It's hard to find HV diodes over say 1,600V as Mouser, Digi-Key, Newark don't offer them. NTE Inc. has some like NTE541 or NTE638 but these are expensive TV repair parts. Not sure what you have for suppliers out East.
                        I would go with 4 replacement identical diode strings, the different Vf on the old pairs is suspect - but a failed diode should cook unless that fuse is fast. They might sorta work but be damaged.
                        I can make 2,000VDC with car ignition coil or a CCFL backlight inverter etc. and use a string of 1MEG resistors as a poorman's HV probe.

                        Comment


                          #13
                          Re: REILs HV PSU runway end identifier lights repair

                          Mouser do have some but most are out of stock.
                          Here is an example that might be ok for low current testing while not breaking the bank:
                          https://www.mouser.se/ProductDetail/...k7piAtYA%3D%3D

                          Then to replace it with something of better quality and better matching I would use a bridge rectifier, but at these voltages they don't come cheap.
                          But if it is a repair for a customer I guess it is no problem:
                          https://www.mouser.se/ProductDetail/...v2ru5yQ2i80%3D
                          "The one who says it cannot be done should never interrupt the one who is doing it."

                          Comment


                            #14
                            Re: REILs HV PSU runway end identifier lights repair

                            I don’t think 0.25A is going to cut it. 1A is better, but still a bit low.
                            Mouser, Digi-Key and Newark are no problem here, even Allied is all right. Haven’t looked at LCSC yet. Never ordered from them.
                            I thought about using a string of meg ohm resistors in series… however I have to find some parts first. Thought about AliExpress too, but do I really want to put some funky Chinese part in there that goes bang because some idiot sells rejects? Probably not.
                            Last edited by CapLeaker; 07-10-2022, 09:50 AM.

                            Comment


                              #15
                              Re: REILs HV PSU runway end identifier lights repair

                              Those orange 0.1uF 1000V caps and the other one across the bridge rectifier xp541’s are good. I took one bridge rectifier assembly out, and checked that diode that someone had replaced before.
                              Hopefully someone can explain this to me:
                              Some tech had replaced one of the XP541 diodes with an PH1021 diode. Whatever this thing is… can’t find nothing about this either.
                              Last edited by CapLeaker; 07-11-2022, 06:45 AM.

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