Dapol Class 121 Head Code Lights

[Roy Whitgrove]

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.

Thanks

i
i had the same problem, I switched decoders, if I remember right I’d bought a loco together with a Gaugemaster decoder, switched them round and the headcode boxes work fine and the directional lights.

[Paul-H]

Sorry I know this is an old post but I am also having the same issue with a new class 121 just received which must have been old stock in the shop as it was the 6 pin version, what decoder did you eventually fit to get the directional and headcode lights to work correctly.

Thanks

[Andy Dapol]

Hi,
There is a knowledgebase article on DCC Supplies helpdesk which may help regarding this:

N Gauge Class 121 or 122 Lighting Fix Posted by Fiona F. on 25 April 2017 03:58 PM

If you have an old style N Gauge Class 121 or 122 (6-pin socket), which has an issue with the head code lights, here is a fix for you to carry out to correct this. On PCB, cut one of the brown wires on the soldering point marked R1 connection (brown that goes to the front of the loco with the exhausts, and is the shortest brown) On PCB, cut one of the brown wires on the soldering point marked R2 connection (brown that goes to the back of the loco and is longest brown) On PCB, there is a group of 4 unused solder points, join the 2 wires and solder them to the bottom right soldering pad. see picture attached If lighting is wrong way around. Try the other 2 brown wires on soldering pads R1 and R2. NB: The easiest way we have found to do this is first look at the model with the front of the model (exhaust end) facing away and keep it in this orientation. Your will then find the brown wire leading to the left hand side of the LED which comes from the R1 soldering pad and then the brown wire coming from the left side of the LED to soldering Pad R2. Be aware to see the lighting wires you will need to remove the seating first.

[Paul-H]

Thanks for the reply and instructions Andy
NO sign of the instructions on DCC supplies knowledge base, can you post a direct link as the pictures would be a big help.

Had a quick look at the wiring under the PCB and noticed a couple of things, first the mention of 4 unused solder pads, mine only has 3, the second regards the instructions to cut two brown wires then if those don't work cut the other two, the problem with that is once the first pair of brown wires are removed it's going to be almost impossible to reattach them to the PCB because of the lack of room or access to the pads they wire first soldered to.

So seeing the photos is important before I end up with no lights at all.

Thanks

[Andy Dapol]

Apologies the article was intended as an aide-mémoire for engineers, I have added the photo to my reply above which completes the note.
Unfortunately there were many versions of the PCB before it was standardised as a next-18 socket type and some further confirmation of the connections would be required.. Difficulty in access is, sadly not something I can assist with remotely. If you have doubts in being able to carry out the work, I suggest that you either return the model to your dealer or contact DCC Supplies who would be happy to carry out the work for you (you will need your proof of purchase).

[Paul-H]

Thanks Andy

Mine is wired quite different to the one in the picture, on mine the pairs of brown wires are soldered to the pads with the white wires, unless the picture is showing them after they are moved but on mine the outer pads have the red and black wires from the track.

In the end I took the easy route as all I wanted was the headcode to come on at one end as it was being pushed backwards by the motor unit. to achieve this I disconnected the two blown LED wires at the pcb and moved them to the top of the PCB were pads are available for a direct connection to the decoder, so I connected the LED Anode to pad 3 and the Cathode to pad 5 via a 1K smd resistor.

Its now working as I need it.

Thanks for your help with this.

[Andy Dapol]

Glad to hear you've sorted it to your satisfaction!
The many variations is one reason I am slowly trying to standardise where possible. Hopefully your notes above will help others with similar models.