Tester for 8 Pin socket in Loco

[Deem]

Hello

I hope everyone is ok and enjoying there time in modelling. I have a question and would be grateful for any help in advance.

I have blown 4 decoders since last couple of days after changing the wiring in Loco (Flying Scotsman with DCC ready and can motor in Loco), wiring was quite messy so I thought I would change the wiring) I installed the X9084T in loco which is socket with blanking plate and wiring, 2 wires to attach to motor, 2 wires to attach to pick ups from or on loco chassis and 2 extra wires to draw bar assembly with, pick ups in Tender as well.

My mistake was, I thought red wire is positive and black wire is negative from chassis pick ups, Loco would run fine in DC mode with this wiring, initially loco was running wrong direction (that should have been a clue but I didn't notice) so I swapped the wires on motor, but in DCC mode all decoders got burned.

I realised much later, so after I swapped the wires around,

right pick up to pin 8 on socket

left pick up to pin 4 on socket

Motor + or right to pin 1 on socket

Motor - or left to pin 5 on socket

I am just wondering if I can buy a circuit board or device which I can install in 8 pin socket in loco to test the wiring before installing the decoder or decoders?

[Fishmanoz]

Don’t have a tester for you but do have a strategy for testing.

First - correct pin assignments - scroll down https://www.brian-lambert.co.uk/DCC-Page-1.html until you find them

Second - any connection between red or black to orange or grey (pickups to motor output) will blow decoders instantly. This is probably the mistake you’ve made.

Third - swapping red and black makes no difference to loco direction but swapping orange and grey does.

Finally, the first order check is that it runs on DC with the blanking plate but that isn’t conclusive as you’ve found.

[rpjallan]

Just hardwire the decoder. The It's quite easy. The sockets are more trouble than they are worth.

[ColinB]

You will realise what trouble hardwiring a decoder is when you have issues with the loco and want to run it on DC. The thing to remember is the connections are diagonal. Motor is 1 and 5, track inputs are 4 and 8. It doesn't matter which way round the track inputs are as the decoder bridge rectifies this. It will make a difference on DC, the loco will run backwards. Get the motor ones round the wrong way and again the loco runs backwards. I test with a multimeter set on ohms with sound on, then test adjacent pins for a short. The Hornby sockets are really easy to inadvertently put a thin solder connection between pads, so you need to test between all adjacent pins. You should only measure a low resistance between pins 1 and 5, which will be the motor. Now check that neither pins 1 or 5 are connected to the track. Make sure the DC header is out. I blew up loads when I first started, this check takes about a minute.

[Fishmanoz]

From Colin - different words, the same testing strategy as I suggested. Read the posts together.

[ColinB]

The only other thing I have to add is if possible get the latest X9084T socket. The early ones are a pig to solder to and because of the way the PCB is make are more susceptible to creating solder splashes (thin string of solder connecting two tracks together). The later ones are tinned with plated through holes and much easier to solder to.

[Deem]

Thanks all.

@Fishmanoz - (Third - swapping red and black makes no difference to loco direction but swapping orange and grey does)

This swap was on only DC mode.

@rpjallan - hard wiring is not an option, as I am expanding my Loco's, so having hard wires is very restrictive.

@ColinB - pointed correctly by you and Fishmonaz, now I have learned the correct pin setting or wiring on the socket, the hard way and wanted to check if there is any thing available but nothing so far. Maybe I can try to make one, on same principal, as decoder tester but reversed to check the socket on DCC track.

Is this wishful thinking or even possible.

Regards

 

 

[96RAF]

When I caravanned I had a test board with lights that plugged into the car sockets to simulate the caravan lights and power for fridge, etc to prove the car side, but also allowed the caravan wires to plug in to check that side out as well.

What you need is a blanking plug fitted with leds (and resistors) to indicate motor function and other function outputs, as you say a kind of reverse logic ESU decoder tester. Should be easy enough to make on vero-board attached to a matching plug.

[Deem]

Thanks Rob.

At least we are on the right track.

I have 3v-12v led with built in resisters in wiring, in red, white and yellow colour. These are 2 big to use in class 08 or Class 20, as I have plenty, might as well use them for some thing else.

Any chance we can drew a wiring diagram to test the loco.

Regards

[96RAF]

At least we are on the right track.

I have 3v-12v led with built in resisters in wiring, in red, white and yellow colour. These are 2 big to use in class 08 or Class 20, as I have plenty, might as well use them for some thing else.

Any chance we can drew a wiring diagram to test the loco.

 

 

I am sure one of our electronics aces can come up with a scheme for you, based on an 8-pin plug. One of Chrissaf’s lost diagrams would have been ideal.

[Deem]

[Deem]

I have uploaded a pictures, just to test the idea. Maybe I am wrong or right. Lets see.

[Deem]

Loco moving backward and LED lit up, showing power from track in white LED and showing power to motor in red LED.

Loco moving forward and doesn't show any light as power is not coming in correct polarity to LED.

[Deem]

More pictures uploaded and once approved, hopefully showing blanking plate with 2 LED attached to it.