X9242 motor issues

[Deltic Man]

Chris, finally been able to upload a photo of the reverse of the X9788 Board/media/tinymce_upload/3e967b1ef0cf13fe6daa5acf1afc24f9.jpg

[Chrissaf]

Do you or anyone have a wiring diagram for the pin positions ??

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This previous post might help.

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https://www.hornby.com/uk-en/forum/post/view/topic_id/19201/?p=2

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[96RAF]

Chrissaf, UPDATE.... found my X9788. Now looking at the underneath of the board, I take it RT is Right Track, LT is Left Track, M+ is Motor Positive and M- is Motor Negative. Assuming this is correct, the fly wires I have out of the plus are : 3,5 & 6 which I assume are blue, yellow and white on a decoder. Do you know what I need to connect to what on the lighting boards of the class 50 (X9252)

 

I would be loath to assume there is a blue connection at the lighting boards as some pcbs use the blue from the socket to power the pcb which has electronic components that mean what logically would be a positive at the lights is actually a ground, with the usual white and yellow switched negatives providing on board bias to light the leds. Have a look at pin 7 of the socket and see where it traces to on the pcb if you can.

[Chrissaf]

What Rob is trying to say. Is that some PCB boards may reverse the polarity of the output feeds to the LEDs. Such that instead of having a fixed positive with switched negatives (what the decoder provides). The PCB board might provide a fixed Ground (negative) with switched positives to work the LEDs. In other words there is no fixed positive polarity output wire connection on the PCB to the outside world (i.e outside the PCB board). It is hard to explain, but this reversal of polarity in the PCB circuit design can make it easier for a loco PCB board to support both DCC (with a decoder) and a DC Analogue (with a blanking plug) installation.

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In order to ascertain whether any particular locomotive PCB board employs this reverse polarity technique. It is essential to undertake extensive testing of PCB output 'connection point' polarities with a meter before making connections based upon assumptions [A 'connection point' in this context may be a pin on a connector or a wire tag on the PCB].

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This of course requires a board to be connected to power on its input. The easiest way to do this would be to fit a blanking plug (plate) to the decoder socket. Apply a DC voltage (say 9 volts) to the connections identified as being the ones associated with the wheel pickups then measure voltages across various PCB pins / tags to determine their function.

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Note that some output voltages on PCB LED feeds may be as low as 3 volts. Once all the various pin / tag to pin / tag voltages are measured and tabulated on paper. Then reverse the input voltage polarity and perform all the measurements again, noting those that are different. It is expected that directional lighting will create a situation where different wire termination pins / tags will have voltages on them or not dependant upon the polarity of the input (simulating loco forward / reverse) direction.

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If this all sounds complicated, then that is because it is.........to fully analyse the results of the measurements, one has to have a basic understanding of what the PCB board is doing in the loco. Methodical and logical thought processes are needed to perform this task effectively when there are no circuit schematics to refer to.

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[Chrissaf]

Overnight I did a lot more digging about. I came across some wiring information for a completely different Hornby PCB, but the similarities to your X9788 board are too close to ignore. I have created a new image as an amalgamation of your image overlaid with the wiring info I found elsewhere. I am not guaranteeing that the pin function shown below is 100% accurate, but it is a starting point for testing connector pin conditions when the board is powered up. Assume that the two +3 volt switched LED outputs are for 'Directional Lighting' and are switched positive in response to loco direction i.e they toggle, when one is on the other is off. Use the powering up and testing methodology described in my post above timed @ 23:45

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As far as I can tell by looking at the PCB tracks (when image is magnified), the wire termination tags in the four corners marked RT & LT look to be in direct connection with the RT & LT pins on the 8 way JST connector. Not sure why these would be duplicated this way, but maybe so the board can be used commonly in different loco types.

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/media/tinymce_upload/4c7870cb8f21e33d22279d6172cf0bd6.jpg

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Note: To get a better (exploded) view of the image. Right click it, and you should get (subject to browser being used) a 'view image' option or similar. This should then place the image on its own in a new tab that can then be zoomed in on.

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Hope this helps.

[Deltic Man]

Chrissaf, many thanks for your continued efforts. I have rebuilt the loco after having tested the Track/motor connection, with a blanking plate in, all seems good via a 9v battery. I have even managed to get the tail lights working, but the headlights evade  me. Is it possible that the headlamp circuit is only complete once the body has been refitted and the connection is made for the marker lamps ??

[Chrissaf]

Is it possible that the headlamp circuit is only complete once the body has been refitted and the connection is made for the marker lamps ??

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If that was the case I would think that it would be fairly obvious from a visual inspection. I am not the best person to ask this question as all my Diesels are Bachmann. I only have two Hornby locos and one of those is an A4 Pacific, the other an 08 Shunter. I am not familiar with what is the normally expected operation for Class 50 front and rear lights arrangement.

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If the body shell comes away completely without any attached wires going back to the main chassis. Then the connections to lights are usually via bronze / copper springy contacts. But that would be visually obvious by even the most casual observer.

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If however, the body shell when removed is still attached by wires I would think typically via 'plug n socket' arrangements, then I would not expect that electrical spring contacts would also be present as well. Look inside the body shell, any electrical contact areas that match up with contacts on the chassis should be obvious.

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PS - If you have got a blanking plug fitted and you are using a 9 volt battery to test. You say the tail lights come on (red?), but not the headlights (white?). Did you reverse the 9 volt battery polarity to simulate the loco in the other direction to see what happens then. If something different happens, then that might give a clue.

[Deltic Man]

Chris, yes they do, but I haven’t made any permanent connections to the lighting yet as I wanted to make sure............measure twice,cut once  y’know

[Deltic Man]

Many Thanks to everyone who contributed to this post. Everything in now connected and working as it should.

So, with that in mind, if anyone gets the problem in the future, I can confirm that X9788 can be used as a replacement PCB for these early DCC Class 50 Locos. (R2350 etc)

The Tree wires at each end connect to the Lighting Boards (X9252) as follows:

PIN 3 = Black Wire, Top Led (Red)

Pin 5 = Red Wire, Bottom Led (White)

Pin 6 = Red Wire, Top Led (Red) + White Wire, Bottom Led (White).

The marker lamps are powered by the copper spring clips on the Lighting Boards.

I hope this helps anyone who is struggling with this issue