Hornby Class 56 PCB wiring

[Irishthump]

 

/media/tinymce_upload/c87cc533d6faa941548e1939a4840e00.JPGHi,

I am installing a Class 56 DCC ready PCB in a kit built loco and I need some help with the wiring! Specifically I need to find out which solder pads correspond to lighting functions, and also how many different lighting functions can be supported.

I have attached a photo of the PCB:

I know that tabs 3+4 are for track power and A+B are the motor terminals. I'm also pretty certain that 6 is the common for lighting functions.

I first want to set up the loco for directional marker and tail lights. I have white and red LEDs installed at each end with the necessary resistors. After that I may add headlights (which are fitted above the cab) at a later date if enough functions are available. The decoder will be a Loksound V4.

Thanks in advance.

 

 

 

 

 

 

 

[Rog RJ]

Why bother with the PCB?  I'd just wire directly from the decoder to the lights, via resistors of course.

[Irishthump]

Why bother with the PCB?  I'd just wire directly from the decoder to the lights, via resistors of course.

Hi,

1)I try to avoid hardwiring decoders whereever possible as it allows them to be changed more easily.

2)I also heavily modified an Athearn chassis for this build and have been checking the running qualities using cheap decoders. The pcb makes it much easier to change these out.

3) I dislike the maze of wiring created by this method and wanted to keep things as neat as possible.

[Chrissaf]

I recognise the board as a X9788. I have never ever seen a a diagram or schematic for this board showing what connects where. In essence you are relying on somebody who has a loco with this board fitted, opening up their loco and tracing out all the wiring. A bit of a long shot if you ask me. Of course, you might be lucky and find a forum member who has done this already and can post their findings.

.

If it was me, I would using a meter to try and back engineer the board. The 8 pin socket on the board has known pin functions. So the first task would be to use an ohmmeter to see if there are any direct connections between the PCB wiring points and the 8 pin socket (for example track and motor connections, although you seem to think you know what these ones are already). Then stage two would be to connect the track connections to the track output of your DCC controller. Plug a basic four function decoder into the 8 pin socket. Then issue the appropriate function commands and see what wire connection terminals on the PCB go negative. Document (map) all the wiring terminal voltage changes on paper, and then use applied mental logic to decide the function of various wire terminal points. For example at least one of the terminals should be permanently positive to act as the lighting common return. Also the wiring terminals for the directional lighting should change polarity between 'forward' and 'reverse'. By careful logical thought, methodical testing and efficient note taking, it should be possible to slowly deduce the various wiring terminal functions.

.

Peter's Spares sell this PCB board. You could contact them. They might be inclined (if they have one) to email you a schematic or drawing showing terminal pin functions. I would like to think that they have access to that information for their Hornby loco repair work.

[96RAF]

It would be good if Hornby would publish a schematic for these boards, downloadable like service sheets are and based on a board Part Number search.

 

No proprietary data need be published just a simple board outline with the part number as ID and telling of what each connection is for.

 

One of your problems is the Class 56 has had several iterations of board affecting the lighting and the other is some of Hornby's boards are common anode and some common cathode.

 

As Chris says a bit of meter work starting from the decoder socket should get you the 8 basic connections and then its a case of there being duplicate connections at each end for the lights (common, fwd and aft).

[96RAF]

I have some pictures of the inside of my Class 56 on the other PC. I will dig them out and post later.

Rob

[96RAF]

Here you go - not much more help but you know the motor connections are at centre board and from the pictures 5 is empty and the others at each end must be left and right bogie pickups, common power (blue), white and red lights, so it should be fairly easy to meter them from tags to socket pins.

Overview...

/media/tinymce_upload/95de38f700d58a3fd59408e68060a375.JPG

 

Fan End...

/media/tinymce_upload/626b9405bc2f957f5df9914281abf759.JPG

 

Decoder Socket End...

/media/tinymce_upload/91fe442c6c32f5715660e9c20b8a174b.JPG

 

If you need more info it will mean taking the top of the 56 and looking for wire colours per tag.

 

Note that my board is R5 and yours is R6.

 

Rob

[Irishthump]

Chris, thanks for the detailed response, your process is the only way to know for sure which outputs are which. But I'm hoping Rob can help me cheat!

Rob, are you saying the outer connections, 1+6 in my pic, are the track connections? If so I have literally got my wires crossed!

[96RAF]

Not at all, a thoroughly bad choice of words by me.

 

I meant to say that you will find these five connections at each end of the board not as it came across in that the pickups would the outer two tags.

 

Sorry for the confusion.

 

My next best assistance will be to take the top off mine and run the same checks either by eyeballing any connections I can to eliminate as many as possible then running the meter across the others. That will be tomorrow now as our clock is two hours ahead of UK.

 

I remember some time ago that I wanted to install cab lights and assumed the empty tags would connect to the green wire on F1 but couldn't get it to ring out, so I left it, then later put a TTS decoder in so it didn't matter.

I also by-passed those springy wire contacts for the directional lights by soldering long curly wires across them and cutting off the springs, meaning I can still take the body off, but it remains connected by those three wires at each end.

Rob

[Irishthump]

Thanks Rob, the confusion was all mine!

If you could do that I would be eternally grateful.

My meter is MIA so I've spent the last couple of hours trying to locate the relevant functions with a wired led.

from what I can see 6 is the common and 5 powers one light function, but the others don't seem to do anything.

[96RAF]

I hope this is clear enough...

...metering has proven I have a couple of broken leads one from each bogie so work to do whilst it's in bits.

 

The motor connections are drawn to indicate their use as the tags are actually wired to the motor brushes and the lines as drawn are pcb tracks.

 

The light contacts are shown as spaced on the chassis two close together and one wider apart. Centre one seems to be the power connection.

 

Colours shown are for clarity not proof of pin allocation.

Metering of the board tags direct end to end is not possible due to interaction of board components so doing checks from the socket was also indefinite.

 

/media/tinymce_upload/7dfa59526c6449760c7e7d044707b7c1.JPG

 

Rob

[Irishthump]

 Rob,

 

I really appreciate the lengths you've gone to in helping me this, thanks again.

I got another reply on another problem which clarified the connections, see below:

 

"DCC socket end

 

1 = Rear Lights

2 = Common 

3 = Red wire Rail on Left side of PCB

4 = Black wire Rail on Right side of PCB

6 = Front Lights

 

Other end

 

1 = Front Lights

2 = Common

3 = Red wire Rail on Left side of PCB

4 = Black wire Rail on Right side of PCB

6 = Rear lights

 

Note

5 is not used at either end

 

the cathode (shorter leg) of the led goes to the common connection."

 

The fact that the common was negative was improtant. The lighting PCBs I had made had assumed a coomn positive so they were never going to work!

I have tested the PCB with a wired LED and my results match the above.

 

Once again, thanks.

[96RAF]

Glad we have that well documented for any similar later queries.

 

I posted in the Workbench thread that I had blown an led tracing the lights and after struggling to get the drivers bench out and the lighting pcb apart I see there is a single red and a white at each end feeding a plastic 'light pipe'. These leds are smd package 0603 (1608) meaning they are 1.6mm x 0.8mm. really tiny parts. I am getting quite good at this micro-surgery.

 

Tag 5 will be used for F1 (function output 3) on the green wire but as it is common negative thats why I could never get it work. The PCB obviously looks after the polarity reversal as DCC relies on common anode for directional lights and function switching.

Rob