TTS lights issue Class 43

[Blue Pullman]

This is a rewrite of a quest I started on the back of a similar thread. 
I have an old class 43 which I bought a twin pack MTU TTS to convert to sound and add lights. 
in both cases I've added a wiring loom and tested the decoders in situ and out using a Lais dcc tester. 
unit one works perfectly sound light etc

unit two works perfectly as above but always has the rear lights on whether it is selected for forward or backwards travel. The headlight responds to forward on backwards off as it should. 
so it's not the loom as alternative looms have been tried. 
any ideas?? Is there some way of changing a cv to control it? Is there a short on the plug wiring making a permanent connection? If I start fiddling here I could spoil any warranty I have  

Roger

[ColinB]

A cv is not going to fix it, you have a pemanent supply to the rear lights somewhere. If you used a socket you probably have a hairline piece of solder between pins 2 and 7, go down the gap with a scalpel or a small screwdriver.  A guy on EBay makes a really nice 8 pin socket which makes the job really easy, why do people not use it when they are retrofitting it to an old model. Another guy makes an equally nice pcb for the pull up resistors. They are not even expensive. It came out too late for my conversion, but if it had I would have used it. There was loads of posts on this forum about HST lights.

[96RAF]

Fiddling with the old loco will not invalidate the TTS decoder warranty which is no-quibble and even includes user abuse.

I would go with Colin‘s suggestion and look under the DCC socket for solder bridging using a magnifier.

I am in two minds as to whether it is worth doing a retro fit campaign of my fleet to replace the standard Hornby socket with something a bit more reliable.

[ColinB]

@RAF96 is there anything around other than the Hornby socket. The only thing is to replace those individual pin sockets with a low profile 8 pin socket, trouble in some locos it makes the dcc header too high. The trouble with the Hornby socket, it is a bit like Veroboard, so easy to get small slivers of solder across ajacent pins, they are also hard to solder to. If you compare soldering to their 8 pin DCC socket to their 4 pin tender socket, they are streets apart, so we know they are capable of making decent boards. Anyway, back to the original subject, normally after soldering to the 8 pin socket I go down the gap between tracks with a fine screwdriver blade, as I used to with Veroboard. If this is the fault the guy is very lucky, it could have so easily been between pins 1 and 8, or 4 and 5 which as we all know is bye,bye decoder.

[Chrissaf]

....you probably have a hairline piece of solder between pins 2 and 7....

 

A short on the 8 pin socket between pins 2 and 7 would not light up any LEDs. Pin 7 is a permanent POSITIVE supply and Pin 2 is a switched NEGATIVE supply. If Pins 2 and 7 were shorted, then when the Yellow wire [Pin2] was switched negative by the decoder. There would be a short circuit between the positive and negative rail voltage on the decoder. This would either cause the decoder to shut down self protect [if it had that capability] or burn out the yellow wire function output.

[ColinB]

Yes, Chrissaf you are right, so it must be short somewhere else, unless of course pin 2's driver has gone short circuit, but then that would show up when he changes decoders. It could be a short between pins 2 and 6, that would do it, but then the front lights would be on all the time. As I said, go down the gaps between tracks with a fine tipped screwdiver. The other thing has got to be the wiring to the leds on the loco, this is the only other thing that is unique to each loco. The biggest issue when I did this was preventing the wires on the leds (I used tower leds) getting ripped off when I put the body on. I never asked what sort of leds are you using, individual ones or two leds in one package (bi colour led).

[96RAF]

@RAF96 is there anything around other than the Hornby socket.

To quote you ... I was hoping for a live link to there.

 A guy on EBay makes a really nice 8 pin socket which makes the job really easy, why do people not use it when they are retrofitting it to an old model.

 

Apart from the LiaisDCC knockoffs, which I will not use on moral principle, I found this one...

https://www.strathpefferjunction.com/product/8-pin-decoder-socket-hard-wire-adaptor-dcc-8-pin-nem65-socket-with-solder-tabs/

 

[ColinB]

@RAF96 the trouble with those is they are usually too wide. There is a guy in Medway that advertises on EBay that does one, but again it is too wide. Generally they also don't seem to have fixing holes. There was a guy at work that used to do PCBs I keep meaning to ask him about making one, or alternatively when I get finished with my railways immediate issues sitting down and looking for a cheap package to do it. I did the course about thirty years ago but I think they are a lot easier now. I want one with plated through holes so you can solder the wires either side. That was why I wanted to know if there was a patent on the design.

[96RAF]

Colin

GM and others similarly do what they call a compact socket  (Image RS Electrics)

https://images.app.goo.gl/HUvZ2ZLQLyao9E8x9 

and there is this one which is quite neat.

https://images.app.goo.gl/

Hornby do the original socket (individual receptacles) and now one that is described as ‘refined’ (Block receptacles).

[ColinB]

I bought some of that second link you sent, that is how come I know they are too wide. I suppose you could file them down. The thing is why make them so wide, surely just opening any tank loco you can see the optinum size. I think you might even be pushed where the socket is in the tender as it hits the back of the tender. The Hornby one is quite compact, it just needs making out of a better material.

[Blue Pullman]

Thank you all for your comments.   In the meantime I phoned Hornby after a long wait not a lot of help as 'Chris' hadn't had the issue before but advised to write in to technical support whose auto response says they can take up to. 2 weeks to reply. Back to my problem and answering comments. I bought 10 pre wired sockets and the issue works with three of them I've tried so it's not the problem. I've also got a Laisdcc tester (really nice piece of kit for £30) and same with that. Bear in mind as a pair for HST's one decoder is fine the other not so it is not my wiring nor the purpose made wired sockets. I've an led magnifying lamp and checked with that and had a little scrape around no change - I have to say the soldering is not very goo. My thoughts are the yellow wire is next although on the opposite side to the black and if there is an unseen short this would permanently light the red lamp. I could cut off the hornby plug and solder on o replace ment or even hard wire it What would that do for my warranty??  Interesting to read Hornby would help me out with an abused decoder I have one that died a year or so back. 

[ColinB]

I still think it is something to do with the "in situ" wiring, I think you need to start checking around the rear light connections that are on the loco in question.It is not the sockets you are proved that, so it has to be something unique to the one that has the lights on permanently, the only thing I can think of is the actual wiring on the leds. Why don't you disconnect the rear lights from the socket and attact a separate led just to see if it works properly.

[Blue Pullman]

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I still think it is something to do with the "in situ" wiring, I think you need to start checking around the rear light connections that are on the loco in question.It is not the sockets you are proved that, so it has to be something unique to the one that has the lights on permanently, the only thing I can think of is the actual wiring on the leds. Why don't you disconnect the rear lights from the socket and attact a separate led just to see if it works properly.

Interesting thoughts but the same issue if it's only plugged in to the dcc decoder tester if it's in three different engines and if it's on a made up bread board. In all cases the other decoder works fine and another make of decoder is also fine. I'm trying to upload a photo showing just that led on. The LEDs are normal red or white ones using 220 resistors. 

[96RAF]

Whilst the TTS warranty is basically no-quibble I believe their stand is that if the plug is cut off they cannot test it so that could invalidate the warranty.

[Blue Pullman]

Whilst the TTS warranty is basically no-quibble I believe their stand is that if the plug is cut off they cannot test it so that could invalidate the warranty.

I think I agree with you I'm sure they would just want to plug it in and test Not try resoldering. Going back to Colins idea of it being my socket I've tried it in 3 different sockets and the Laisdcc test unit all with the same results all these work perfectly with the other one of the pair and their usual decoder   

though I've looked under an led magni lamp and gently pocked about I can see no cross connection  

I wonder if it could be as they are next to each other although on opposite sides the yellow wire shorting to the black?

 

[ColinB]

I would have thought yellow shorting to black would have blown up the decoder, but I am not entirely sure. I think the easiest solution which is what I would do, is disconnect the wire that goes to the rear lights and just wire in a separate led and see if that works properly, then take it from there. Are you checking any of this with a multimeter? If not I seriously suggest you do. 

[Blue Pullman]

I would have thought yellow shorting to black would have blown up the decoder, but I am not entirely sure. I think the easiest solution which is what I would do, is disconnect the wire that goes to the rear lights and just wire in a separate led and see if that works properly, then take it from there. Are you checking any of this with a multimeter? If not I seriously suggest you do. 

Hi Colin 

I think I've read somewhere that 6 pin decoders don't have a blue wire but go straight to black to make the circuit so that's why I'm not thinking  it would create a short. I agree with you I could use say the green wire and have that separate from the built in function but then I'd lose my cab light. I have used my multimeter but with no obvious result. I'm away from home now so it'll be a few days before I can have another scrape round. 

maybe hornby tech might come up with an answer without a two week wait 

 

[Blue Pullman]

I've now had a reply from Hornby. I have registered to send the decoder back to them however they aren't accepting any returns at present so I'll have to wait until they advise me I can which from what I see of Covid could be months. 

[96RAF]

Odd there is such a wait as a friend has just arranged with them by phone about sending his Select back for update and his Elite for repair and that all happened earlier this week - his controllers are now in the post to Hornby.