Class 47 TTS lights

[Rickhitch]

Hi all

i have recently converted an old Lima class 47 with a TTS decode. Bit tricky but I got there. All working except the directional lights. They are both on all the time and f0 seems to make no difference.

is it possible I have messed this up with a short or something while converting? Is there any way back?

i have done cv8 to 8 but no luck. Any ideas gratefully received!

[Rog RJ]

If the lights use filament bulbs, you may have overloaded the decoder function outputs.

[Chrissaf]

Have you rewired the directional lights to the white, yellow (switched negative) and blue (positive) decoder wires. If you haven't, then the lights are probably still connected to the wheel pickups.

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Have you also converted the lights to LEDs, or kept them as bulbs (assuming that the Lima had bulbs originally). If converted to LEDs, did you include a current limiting resistor in series with the LEDs. LEDs with an appropriate resistor value can be made to draw less than 5 mA each.

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I ask these questions because your post lacks any useful detail in it.

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As Rog(RJ) says above, bulbs draw a lot of current, typically about 60 mA to 80 mA per bulb (far more than the LEDs that decoders are designed for). So assuming two bulbs at the front and two bulbs at the rear then that equates to about 240 mA to 320 mA on a decoder function (white wire - forward direction) that has a maximum 100 mA specification --- see TTS leaflet extract image below. And another four bulbs drawing >200 mA on the yellow - reverse direction decoder wire. The function wires might possibly (as Rog says) have blown the output semi-conductors to a permanently on 'short circuit' state.

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Note the (Unprotected) comment in the yellow highlight. This means that the function outputs do not shut down to protect themselves when over-loaded and just burn out.

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When you do your own conversions, it is more than just getting the basic wiring correct. You have to take into account the decoder specification and the electrical current limits of the decoders and what you are connecting them too as well.

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[Rickhitch]

Hi

thanks for the quick responses. Should have been a bit clearer.

The conversion uses LED with 1k resistors. Yellow and White (paired so the opposite tail marker comes on with the headlights). Blue as common.

i have done this once before and it works fine. The load should be well within tolerances I believe. I can only think that I created a short when trial fitting it and it has damaged the decoder so both yellow and white remain “on”.

[Chrissaf]

Yellow and White (paired so the opposite tail marker comes on with the headlights). Blue as common.

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Above statement still a bit vague in my interpretation, regarding your use of the term paired. You should not directly join the white wire to the yellow wire, if that is what you meant by the 'paired' term..

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This schematic below is what I would consider to be the optimum wiring of the conversion of a non DCC Ready loco. That includes the fitting of a socket as part of the conversion.

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[Fishmanoz]

Might I try restating the question and the answer?

 

Question - I’ve fitted a TTS decoder to my Class 47 including directional LED lighting.  However, all lights remain on all of the time irrespective of whether F0 is on or off.  What have I done wrong?

 

Answer - the correct wiring diagram for the conversion is as above.  Have you accidentally made a connection between the white and yellow wires?  This would mean all lights remain on irrespective of direction, all powered by the white wire forward and yellow wire reverse.

 

Do I have this correct for both of you?  If so, there seems to be an unresolved problem not answered as F0 should switch them all off or all on.  And the possibility of a short during installation causing this fault is unlikely.  It is more likely to have caused an overload and burnout rather than have caused the switching function to fail leaving all lights on.