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TCS FL4 decoder issue, please help


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HI guys I need your help


I have just finished installing a TCS FL4 function decoder in my Tsubame 800 front car and lights work strangely



my kato lightboard is 4352


I have reversed the red led as shown in the picture, in this way I have both anode on the same side, I have cutted the trace as signed (I hope I have cutted them well) and connected the wire properly, the only difference is that I used green and purple wire instead of white and yellow because this is a function decoder and does not have withe and yellow wires


now my problem is that when I use F1 the white light turn on correctly, as soon as I turn on red lights with F2 the whote light goes off and until I turn red light off there is no possibility to have the white light on again


If I remap F1 to FoF and F2 to FoR to manage the light as front and tail light only the red light are on and there is no way to have the white light on


I have attached the PDF files of the decoder


can you help me spot my error, my head refuse to find it, so I need someone else that review my work and point me to the solution


thanks to all


Comprehensive Programming Guide.pdf

Edited by Melandir
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Answer is found in CV program.


Key understanding.


The original light board is DC. The train has 2 light boards. One on each end. because train is bi directional front depends on voltage flow.


the lighting board has 1 circuit with 2 LED lights. Lighting logic is controlled by voltage direction. When voltage flows the white light is on the lead board. remember the red led had the anode reversed. this makes the red light on rear boards laminate because the polarity is reversed.


When you cut the traces on the board you are making 2 circuit on one board with each having their own LED. When you do this you lose your light logic. Now you have to program that same light logic into the FL4.


White and yellow lights are program in CV 49 and 50. These are associated with F0F and F0R.


FL4 purple and green is 51 and 52. You must write down the light logic that you want and activate the purple and green light to follow the light on the opposite FL4.


Making the FL4 a consist is the key.

Edited by inobu
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Inobu, I have reversed the red LED to have it work with the same polarity of the white LED and connected both anode with the blue cable including the resistor on the lightboard, my issue is that currently if I turn RED led (F2) on, it automatically turn off the white one instead of having both of them working togheter


this evening I'll review the cabling in case I made some mistake and will post some photo maybe that could help

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You have to use separate resistors for each led, since when they are connected parallel to the same series resistor with the same polarity, then only the one with the lower turn on voltage would light up. This is not a problem if they are connected with reversed polarity, so many bipolar light boards use only a common resistor.

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Thanks KVP I'm now near the resolution of the issue, it's ok that they cannot be on at the same time

RED turn on at 1.9V, WHITE at 3V, but I need white or red on depending on train direction of travel.


I now need to fix the decoder config to have them work correctly with train direction so when I face forward white On and red Off and vice versa.


Since I don't have anything that use power the digital station cannot read the CV, I have to work blind and guess what it's not working

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Issue command F0F ------ Green wires Light

Issue command F0R ------ Purple wires Light



Consist all decoders together                     FL4-A    --------------    Motor Decoder  ------------------- FL4-B


Lighting logic is the instruction you program on a given command. 


It is difficult until you break it down into logical steps or instruction

Binary number are the basic element that a chip or computer uses to folow instruction like 10000000 or 01110000 11111111. these are number that mean something. A 1 represents a flag or ON state and 0 is OFF or no flag.    


Location #           1st             2nd          3rd            4th        5th            6th       7th          8th

Binay Value         1                2               4              8          16              32        64         128

Binary Flag          *                 *               *               *            *                 *          *             *


                         White        Yellow        Green      Violet         Brown     W/Y       W/G     W/B

CV33   (F0F)       x                                  x

CV34   (F0R)                          x                                x


CV33 will be       1                  0               1              0              0             0             0           0

CV34 will be       0                  1               0              1              0             0             0           0


When the decoder sees the command F0F it will read CV33 register and find the value


The color map ties the values together. The decoders looks at the bianary number


10100000 and matches each flag with a color. In this case a 1 in the first location is White and a 1 in the third location is Green based on the color map.


So when you enter the decimal value of 5 into CV33. The decoder knows to apply voltage on the

White and Green wires when the trains moves forward or F0F. Binary 10100000


Because the FL4 does not have white or yellow wires then the first 2 flags are over looked. 


Figure out the next color and binary number. 




The answer for CV34 is the Decimal value of 10. The binary value of 01010000

Voltage will be applied on wires Yellow and Purple/Violet


How did we get the value of 10.


1   2   4   8  16  32   64   128


0   1   0   1    0   0     0      0 


Add each flag ------------ 2 + 8 = 10

Edited by inobu
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Thanks Inobu


I have now solved, this is the solution to my issue with the FL4


CV 35=1
CV 36=2
CV 51=0  default=32
CV 52=16 default=32


CV35 and 36 are the funcition remap, to move green and purple wire from F1 and F2 to F0F and F0R

CV51 and CV52 are needed to program the lights related to direction


EDIT: everything work but the decoder does not want to change adress, it's fixed on adreess 3 I need to work on this issue

Edited by Melandir
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It does not look like it is going to function automatically but Se tu contento Io sono contento. Parola



With my solution it works, I nave tested it

The light switch works automatically based on train direction and lights are controller with F0, now I only miss how to change the address of the decoder I need to look in the lock unlock section of the programming guide

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Issue finally solved evertyhting work now as expected


to solve the address problem I needed to operate on the single CV one by one instead of using my digital station address programming were I simply put the Loco address and it take care of all CV

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