DCC on a split chassis

[Black5]

I `ve spent a couple of days now going through the process of fitting a decoder to a Bachman parallel boilered Scot, with a split chassis.

Dismantling and modifying the chassis to take the decoder, a DCC 25 OPTI standard, went well.

Reassembly was alright with all spacers etc being in their appropriate places. I had to extend the four wires to the motor and chassis and used similar coloured wires to avoid mix ups. I made phos bronze wire tags to solder the track pick up wires to as they are trapped under the two screws that hold the chassis together.

To anyone who knows the motor, it has a tag marked with a red dot to which i soldered the orange wire, the grey one going to the other tag.

The red and black wires were soldered to the chassis tags, the red wire going to the left hand side

, looking from cab to smokebox, with the black wire going to the other side.

On placing the chassis on my test track, start up sequence runs through correctly to 03 but there is no movement when testing for acceleration.

I`ve checked everything i can but can`t see a problem, but i`m wondering if the red and black wires might be on  the wrong sides or would it make no difference?

The decoder is rated at 1.2A-----2A Max but i`m wondering if i`ve damaged it somehow.

I know one test would be to try another decoder but if i`ve done something wrong that i haven`t spotted i might destroy that one as well.

From my description does anyone see a glaring error in what i`ve done?

Cheers just now,

 

Jim.

[Butler Henderson]

I `ve spent a couple of days now going through the process of fitting a decoder to a Bachman parallel boilered Scot, with a split chassis.

Dismantling and modifying the chassis to take the decoder, a DCC 25 OPTI standard, went well.

Reassembly was alright with all spacers etc being in their appropriate places. I had to extend the four wires to the motor and chassis and used similar coloured wires to avoid mix ups. I made phos bronze wire tags to solder the track pick up wires to as they are trapped under the two screws that hold the chassis together.

To anyone who knows the motor, it has a tag marked with a red dot to which i soldered the orange wire, the grey one going to the other tag.

The red and black wires were soldered to the chassis tags, the red wire going to the left hand side

, looking from cab to smokebox, with the black wire going to the other side.

On placing the chassis on my test track, start up sequence runs through correctly to 03 but there is no movement when testing for acceleration.

I`ve checked everything i can but can`t see a problem, but i`m wondering if the red and black wires might be on  the wrong sides or would it make no difference?

The decoder is rated at 1.2A-----2A Max but i`m wondering if i`ve damaged it somehow.

I know one test would be to try another decoder but if i`ve done something wrong that i haven`t spotted i might destroy that one as well.

From my description does anyone see a glaring error in what i`ve done?

Cheers just now,

 

Jim.

Simply crossing the motor wires or pick up wires will not cause any problems apart from the loco going the wrong way. Have you tried resetting the decoder (CV30 =2). If that fails suggest you disconnect the decoder and connect the motor wires to a dc supply to check the motor works (obviously if not, strip down to see what the problem is). You do need to make certain the motor contacts are insulated from the chassis.

[Butler Henderson]

On more advanced chips CV30 tells you if it has detected any errors, like short circuits etc, that may prevent the loco from working properly. Try reading CV30 (if your decoder supports that, it's in the manual if it does) and see what it says.

The only function of CV30 on the Opti is to reset (not CV8 as I had typed - now edited)

[Black5]

Simply crossing the motor wires or pick up wires will not cause any problems apart from the loco going the wrong way. Have you tried resetting the decoder (CV8 =2). If that fails suggest you disconnect the decoder and connect the motor wires to a dc supply to check the motor works (obviously if not, strip down to see what the problem is). You do need to make certain the motor contacts are insulated from the chassis.

Thankyou for your reply. I can say that the loco ran on dc ok before i started this conversion but i will double check all connections again to make sure things are correct. I use a light connected to two crocodile clips to check for continuity. If standing on the track and showing 03 and i take one croc clip from one side of the chassis and the other to one of the motor terminals, would i be right in thinking the light should come on or does that sound like a short somewhere?

Many thanks for your help,

Cheers just now.

[peach james]

Get a multi-meter- although a light will work, the cost of one can easily be justified with most wiring problems...

 

I did an A4 a fair # of years ago- and the trick was making a big enough space for the decoder...the rest of it is simple enough, make sure both motor terminals are 100% isolated to the chassis when you are ready to install the decoder.  Add the wires to both of them (red and black to the track, orange and gray the other way), and don't worry too much about direction- if you get it wrong with the physical wiring, use CV 29 to change the direction.  The key is that there has to be "infinite" resistance between the motor brushes and the chassis half's, then pick up current from the chassis halfs, to the decoder red & black, then from the decoder gray and orange to the motor, and it should all go.

 

I broke valve gear parts when I did mine, but got replacement bits from Bachmann, so it all worked out in the end.

 

James

[Butler Henderson]

One thing to try as odd as it might seem is just to loosen off the fixing screws on the chassis baseplate slightly.

 

Thankyou for your reply. I can say that the loco ran on dc ok before i started this conversion but i will double check all connections again to make sure things are correct. I use a light connected to two crocodile clips to check for continuity. If standing on the track and showing 03 and i take one croc clip from one side of the chassis and the other to one of the motor terminals, would i be right in thinking the light should come on or does that sound like a short somewhere?

That will just potentially short the decoder and probably cause damage. The safest thing to do in the absence of a multi meter is to disconnect the decoder and test the motor works on a dc supply. If the motor works with one motor terminal still connected apply the other power lead to one chassis side then the other, then repeat with the power leads swopped. If the motor starts at any point you have a short circuit between the chassis and the motor,

[Grovenor]

If standing on the track and showing 03 and i take one croc clip from one side of the chassis and the other to one of the motor terminals, would i be right in thinking the light should come on or does that sound like a short somewhere?

That would give you a good chance of damaging the decoder, you should never connect either rail, or the red/black wires, directly to the motor or orange grey wires, and your light is as bad as a direct connection.

Did you wire in your decoder directly or through a plug? To check you have no connection between the motor terminals and chassis you need to disconnect the decoder.

Multimeters are not dear, every modeller needs one. eg. http://cpc.farnell.com/duratool/d03047/multimeter-digital/dp/IN07221

Regards

[Black5]

Thanks to Peach James, Butler Henderson, Dutch master and Grovenor for all your suggestions. I have to admit to having a multi meter but don`t use it that often ( not really being into electrics a lot of the symbols are a mystery to me, really sad i know! ) Even worse is the fact that i still use a Select as a controller  so changing cv`s is a no no i think.

Any way i will try the things you have suggested as far as i can.

 

Many thanks once again.

[Butler Henderson]

Thanks to Peach James, Butler Henderson, Dutch master and Grovenor for all your suggestions. I have to admit to having a multi meter but don`t use it that often ( not really being into electrics a lot of the symbols are a mystery to me, really sad i know! )

You should set it to read resistance (ohm being the unit of resistance and the Greek Omega symbol is used - looks a bit like a horseshoe). There will be variety of resistance ranges the multimeter can be set to, the one in  font of me at present has 400, 4K, 40K, 400K, 4M, 40M and 400M. On this particular meter setting to 400 gives an audible warning when a short circuit (0 ohm) is found. Set yours to the lowest range it has (400 in the case of mine) and touch the end of the multimeters leads together - the display should go to zero and possibly an alarm will sound. Set up as such you can use it seek out any shorts on the loco (etc)

[Black5]

Thankyou for your explanations on the multi meter, but it`s confession time regarding my split chassis installation.

On rechecking all connections and still having no luck it occured to me that this decoder had been put in another loco but taken out again because of lack of room and put back in its packet.

As this had happened some time ago i`d totally forgotten that i`d given it a number and when trying it on the conversion i`d wrongly assumed it was a new decoder, hence no movement. On scrolling up the installed number, you can guess the rest!!

 

To you and the other gentlemen who gave me help, my thanks, but you`ve been dealing with an idiot!!!

The good thing is i now know some of the checks to make in future should i have problems and my first attempt at a split chassis conversion worked. Next step is tender pickups now it`s running.

Many thanks once again. Have a good Christmas and a great New Year,

Jim.