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Dapol Class 121 Head Code Lights

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  • Dapol Class 121 Head Code Lights

    Hi all

    I have just taken delivery of a new Dapol Class 121 and have something I want to check

    I have found the head code LED's although on are quite dim and do not show once the roof is clipped back on, even with all the room lights off, is this normal for this model, not a problem if it is but just wanted to check.

    Last edited by Jeanette-H; 14 November 2018, 12:09.

  • #2
    Anyone there?


    • JeremiahBunyan
      JeremiahBunyan commented
      Editing a comment
      I don't own any Dapol Class 121/122 myself. But I have a few friends who do. I'll ask them and get back to you ASAP.... Hang in there!


  • #3
    Hello Jeanette-H ,

    I've spoken to a couple of people who have said that their headcode lights are also dim.

    Whether that's the way it is or not I am not sure. A few YoutUbe videos seem to suggest the same.

    Hope this helps??

    Jeremiah Bunyan...


    • #4

      Thanks for the reply

      At least now I know I am not the only one.


      • JeremiahBunyan
        JeremiahBunyan commented
        Editing a comment
        Try watching a few YouTube videos....should find your answer there as well. I just watched two

      • Joel Dapol
        Joel Dapol commented
        Editing a comment
        How dim are they?

    • #5
      Very dim, I can only see they are on with the loco top removed, once the top is on, even in a dark room the headcode cannot be seen, the headlight LED's are fine though.
      Last edited by Jeanette-H; 16 November 2018, 10:01.


      • #6
        Just by way of a little update on this issue, I noticed today whilst fitting one of your overbright lightbars that the headcode LED's are bright enough to be seen through the headcode box when it is moving in reverse, and goes dim when forward is selected, also had to change the decoder from a Zimo MX622N to a Bachmann DCC23 otherwise the lid wouldn't go back on with the lightbar in place and that made no difference, so it's not the decoder.


        • #7
          Just spotted I was having a dim moment when posting the original question, its a class 122 not 121, not that makes much difference to the problem


          • #8
            Ok so now I have a Class 122 driven unit and a class 121 dummy, both with the same issue, when travelling exhaust end first neither head code LED illuminates bright enough to be seen in a darkened room but when travelling backwards non exhaust end first the head code LED are bright enough to see with the room lights on.

            Perhaps I am misunderstanding something fundamental with these, which end is the front, exhaust end or non exhaust end?


            • #9
              Not sure if I have solved this or not, but after googling around i have found that the exhaust end is the rear, so if I mount the 121 & 122 rear to rear I now have the head code LED's on at the front when travelling forward then on at the other end when travelling the other way, so head code is illuminated at the front of the loco, still dont know if this is how its supposed to work but its a sort of work around. so may be of use.

              Perhaps someone from Dapol could confirm what I have found is how they were designed to work.



              • #10
                Just by way of a heads up, I have been playing around with decoders in these models and found the following.

                this is with the models used as said above, power unit and dummy placed exhaust end to exhaust end, and is the same with Class 121 & 122.

                with the following decoders, Zimo MX622N, Zimo MX616N, Bachmann 36-558A and Laisdcc
                860013, you get motor control and head and tail light control but no head code lights

                But using the Gaugemaster DCC23 I get motor control, head and tail lights and head code lights but only on the unit at the front, whichever direction it is moving.

                so two questions

                Is it correct that the head code lights will be only on in the unit at the front, how does the one st the back know it's at the back

                why do the head code lights only work with the Gaugemaster decoder?



                • #11
                  What does it do on DC with the blanking plug in place. Reason I ask, is that the 122 and 121 take a 6 pin chip, so the Headcodes must be driven from the F0f and F0r connections. All the chips mentioned supply these yet you get different results. Maybe the issue is voltage / current supply from the chips and it just so happens that the DCC23 is in some kind of sweet spot.

                  Just a thought and hope you get it sorted.
                  Last edited by Vonzack; 6 December 2018, 09:37.


                  • #12
                    Hi, Actually it should work with any of these decoders. Since the model is new I suggest its reasonable to return it to your dealer for replacement. If this is not possible or undesirable for some reason, then contact our service centre DCC Supplies 01905 621999, who will be happy to repair it under warranty. The only exception would be if it has been purchased from a private seller or via an auction site of course.

                    Dapol Staff Member


                    • #13
                      Unfortunately all from the well known auction site, but all 4 with the same issue? that sounds like something has gone amiss in production rather than a random fault

                      Can anyone with either of these models confirm that your head codes are working and what decoder you have used. Still don't understand why they appear to work with the Gaugemaster decoder but not with any of the others!

                      Perhaps someone in Dapol could check a couple of stock items in case its a bigger problem than my 4


                      • #14
                        Following some advice found elsewhere I have checked how you have engineered the connection and power of the headcode LED's and found the following

                        Both Headcode LED's are connected together and only powered from pin 5 on the decoder which is power for the white Headlight LED's so in theory when either white headlight LED is on the headcode LED's should also be on, but as they are not on all 4 of my brand new models supplied by 4 different ebay model rail traders I can only assume that the two headlight LED's are not directly connected together but go through some sort of passive device which is stopping the headlight at one end from illuminating the headcode LED.

                        I have yet to find anyone through many internet searches that can confirm the headcode lights work any different to how mine work, so its obviously a fault in the design of the lighting circuit.

                        None of the above explains why on the Gaugemaster Decoders work the headcodes, with no headcode at all with Zimo, Bachmann (Pre Zimo Version) and LaisDCC who also supply your own Imperium decoder.

                        I don't expect a meaningful reply to this but let it be a warning to others thinking of buying either the class 121 or 122 from yourselves


                        • #15
                          It’s awhile ago since had a problem with these LED’s and I’m not at home to check my facts, but I seem to remember that the Zimo decoder did not work but when I swopped it for a Bachmann decoder it was perfectly ok.