AE 6/6 Roco DCC retrofit

[vignale]

Hello everybody,

 

I have recently gotten back into railway modelling and I am currently updating my old father's locomotives to DCC.

I am running Arduino with DCC++EX base station and JMRI for throttles and such.

 

The first DCC conversion I made is a AE 6/6 from Roco. This was my first hard-wiring of a decoder. I opted for a Zimo MX630.

After completing the installation, the lights are working great and can be turned on/off and automatically reverse based on the travel direction. However, the locomotive does not move at all.

I will give you a brief explaination on the modifications and tests I did on the locomotive.

 

At first the internal PCB was looking like this:

 

From now on I will as the forward direction of the locomotive to the left of the picture and reverse direction to the right.

As you can see, the left rail (based on direction of travel as defined before) is hooked up to the chassis and the other rail is connected to the engine via a V shaped flexibile connector near the coils in the back of the engine. The rotating connector is used to connect to the overhead line if it's used for power instead of the rails.

 

The first thing I did was desoldering all the 4 wires and hooking up the decoder to the front ones, red wire on the right and black one on the left. I then connected the orange wire on the right where the orginal black right rail contact was and the gray wire where the original black left rail contact was. The back rail connections were left disconnected.

The locomotive was picked up on my programming track and moved flawlessly, as expected. The lights were working as in the original configuration, so they turnend on alternatively thanks to the diodes, but shut off if the engine stopped.

I then proceeded to wire the decoder like this in order to gain control of the lights:

 

So the gray wire is still connected to the chassis (it's how the motor picks up power, I guessed) and the orange one to the same V copper connector. Please note that I removed the coils on the right in order to separate the V connector from the part of the circuit that I used as common light connection and the diodes that controlled the lights.

This is where I made a mistake while connecting back the PCB: I missed the motor poles with the V connector and instead of clipping to the motor ends (there are 2 ends to connect to, 0 Ohm resistance between them) it touched the chassis. I did not notice this and tried to move the loco, resulting in the DCC++EX station shutting down as I had created a short circuit between the decoder motor leads.

 

After fixing this mistake, I tried the loco again on my main track. The lights now work perfectly (F0 function, they reverse based on the direction selected on JMRI throttle) but the engine does not move. I tested everything I could with my multimeter. Between the V connector and the chassis there are 0V when the train is stopped, but if I apply throttle it reads +7V or -7V (measured in DC) based on the direction of travel chosen in JMRI.

 

I am now pretty hopeless and do not understand at all why the loco isn't moving. I am concerned the coils and circuitry on the back was required for the DC motor to work and I am unsure if I should put them back in. PWM frequency is at 20kHz. I have a basic understending of circuitry and suspect that the copper coils helped converting the PWM output from the decoder to the motor, as before removing them everything worked just fine. Should I put them back in? Or did I fry the decoder when I shorted the motor outputs?
Please note that I did not change any CV after it was working with the decoder and just 2 motor leads, as I described before.

I have heard old DC motors do not like high PWM frequency. Should I switch to a lower frequency? If yes, what's best?


Thank you to everyone who'll help me, it is much appreciated.
Please let me know if you need any other picture or information.


Best regards,

Alessandro

 

 

Edited September 1, 2021 by vignale
mistype

[Nigelcliffe]

The "coils" you removed are not important. They are part of the suppression for DC running, fitted to stop a loco creating radio interference.   They are not your problem if your connections are now to the motor brush gear. 

 

BUT, I'm not sure where your Gray wire is going.  It is hard to determine exactly what you have done from photographs. 

 

It is possible you blew the decoder with the short circuit.  Zimo decoders are usually pretty robust with overload protection, but there are usually ways to blow any decoder with certain types of short circuit - connecting the wrong wires together on the decoder's outputs.     The only way to be totally sure is to disconnect the orange + gray wires, and attach them to something else which can substitute for a motor, and try it.  

There is a replacement fee for Zimo decoders which have been damaged by user mistakes, it may be a cheaper route than a new decoder.  

 

 

Were it mine, I'd be reducing the length of the tracks on the PCB (by creating new cuts) to limit where there is current for lights and blue wire.   I'd also consider replacing the bulbs with LEDs (which need resistors).   

 

If the motor is "live" to one side of the chassis, I'd be concerned about that - a touch of a wheel against the chassis would lead to a short between pickups and decoder output, this can destroy decoders.   This might require cutting some metal from the chassis block to remove the contact between motor and chassis.  

 

 

 

Motor settings in the decoder are a long way away - get it to work first.   I suspect that when working, you won't need to change much in the decoder settings.  

 

 

 

- Nigel

 

 

 

 

 

 

[Neils WRX]

I’ve converted a few Roco models, the Bo-Bo chassis’s are different from the Co-Co’s and I struggled getting first one to work. You have to pretty much break all connections on the circuit board, as power goes through the screws and chassis.

 

Bo-Bo conversion.

 

 

Co-Co chassis

 

 

Converted chassis

 

 

Hope this helps,

 

Neil

[TPC]

Vignale you have created a short where you have connected you grey wire.  Grey and the orange wire goes to the left & right motor connection tabs of the motor.  The soldering tab just above to the right of the motor tab ( mirror of your orange wire connection) is for the grey wire.  Orange looks like it is on right place. The wheel sets that is not connected(probably the top set on your photo) directly to the chassis, that wire goes to the red wire.   You can connect the black wire to where the grey was as that is connected to the other wheelsets (bottom set) via chassis.  If you want to switch between overhead & track then solder the black wire to the solder point just above where the grey wire is now.  Normally on a live chassis you don't use the blue wire as it does the same work as the black wire. If you isolate the lights , then you use the blue wire.  Not clear what is going on in the top left corner of the light board, screw broken off, missing?  That is the connection point for your lights (positive side).  If not connected with a screw,  then you will have to use the blue wire for the lights.

[John ks]

 

Here is how I would have done it

The top image requires removing the 2 diodes & the 2 Coils (which you have done) & cut the PCB (printed circuit board) tracks in 2 places & add the red jumper wire as shown

This isolates the 2 lights from the rest of the circuit  & gives a place for the blue wire to be connected.

 

If you want to isolate the chassis from all electrical connections then the option is to cut the PCB track & extend the wire from the rear bogie to the front bogie connection

 

The lower image shows the lights wired for half wave operation, still requires removing the 2 diodes & the 2 Coils

 

This wiring allows the loco to still pick up power from the catenary if that is wanted

 

 

Don't forget to put the OH/Tk switch into the track position

John

Edit 

Here's one i prepared earlier,

the big difference is that i treated the RH end as the front so red/black, orange/grey & white/yellow are all swapped as compared to the above images

The blue wire with the green & purple wires from the decoder are not connected are terminated in the heat shrink near the left end of the pic

 

 

 

 

Edited September 3, 2021 by John ks

[SRman]

21 minutes ago, John ks said:

 

Here is how I would have done it

The top image requires removing the 2 diodes & the 2 Coils (which you have done) & cut the PCB (printed circuit board) tracks in 2 places & add the red jumper wire as shown

This isolates the 2 lights from the rest of the circuit  & gives a place for the blue wire to be connected.

 

If you want to isolate the chassis from all electrical connections then the option is to cut the PCB track & extend the wire from the rear bogie to the front bogie connection

 

The lower image shows the lights wired for half wave operation, still requires removing the 2 diodes & the 2 Coils

 

This wiring allows the loco to still pick up power from the catenary if that is wanted

 

 

 

Don't forget to put the OH/Tk switch into the track position

John

 

 

 

Yes, as John said, put that pantograph/track power switch into the track position.

I also did this conversion last year, but I replaced the bulbs with LEDs and associated resistors as well. Note he position of that switch in my photo: I soldered it lightly to the PCB track to prevent it being accidentally moved and causing problems. It is at the bottom end of my photo.

You may be able to make out in my photo how the orange and grey wires are soldered directly to the brush connections.

[vignale]

Hello, thank you all for the great suggestions.

 

I made the wrong assumption that the motor was picking up power directly from the chassis (yeah, I realized that it is normal for a DC motor to have 0 Ohm resistance between the two power leads). I moved only the gray wire and now everything is working perfectly.

 

On 03/09/2021 at 09:18, John ks said:

 

Here is how I would have done it

The top image requires removing the 2 diodes & the 2 Coils (which you have done) & cut the PCB (printed circuit board) tracks in 2 places & add the red jumper wire as shown

This isolates the 2 lights from the rest of the circuit  & gives a place for the blue wire to be connected.

 

If you want to isolate the chassis from all electrical connections then the option is to cut the PCB track & extend the wire from the rear bogie to the front bogie connection

 

The lower image shows the lights wired for half wave operation, still requires removing the 2 diodes & the 2 Coils

 

This wiring allows the loco to still pick up power from the catenary if that is wanted

 

 

Don't forget to put the OH/Tk switch into the track position

John

 

 

 

This has been really helpful. Currently my wiring looks the same as the top image, except I only connected the red/black wires to the front bogie directly without connecting track power to the PCB.

This is because I am implementing ABC braking on my layout and connecting both the front and rear bogie would mean that the ABC braking signal get picked up by the controller when both bogies are in the isolated section, so when the rear of the locomotive gets in the braking zone. This is not ideal when using constant distance braking, as it would mean that a shorter loco will stop before a longer one.

 

Please tell me if my reasoning is flawed. I have yet to test it on the full layout with turnouts and they might pose a bit of an issue if they can’t transmit power properly. I will let you know how testing goes and if needed I might wire back the rear bogie power leads just as in your first picture.

 

On 03/09/2021 at 09:47, SRman said:

Yes, as John said, put that pantograph/track power switch into the track position.

I also did this conversion last year, but I replaced the bulbs with LEDs and associated resistors as well. Note he position of that switch in my photo: I soldered it lightly to the PCB track to prevent it being accidentally moved and causing problems. It is at the bottom end of my photo.

You may be able to make out in my photo how the orange and grey wires are soldered directly to the brush connections.
 

I had considered replacing the light bulbs with LEDs, however I find that creating a new solder joint on the old PCB is extremely hard. Solder just doesn’t stick, and this is also why I only connected the new wires where old solder joints were. Any tips for that?

 

Thank for the LED suggestion; I would love to get brighter lights and LEDs are a great way to do it, but also like the warm feeling of incandescent bulbs. Are yours standard white? I can’t seem to find any warm white single LED, they only come in long strips of 5050 bulbs.

 

 

Also, when running at high speed the transmission emits a tickling sound which is extremely annoying and gets amplified by the plastic chassis when put in place. I believe it comes from the main transmission axle touching something around the rear spring every rotation. I am sure there are no wires interfering with it and can’t locate it exactly. Be aware that the loco hasn’t been run in about 10 years, so it might just need a bit of stretching. I am yet to deploy the old layout where I can take her for a long spin.

 

 

Thanks again for the lovely feedback,

Alessandro

[Nigelcliffe]

30 minutes ago, vignale said:

.......

Currently my wiring looks the same as the top image, except I only connected the red/black wires to the front bogie directly without connecting track power to the PCB.

This is because I am implementing ABC braking on my layout and connecting both the front and rear bogie would mean that the ABC braking signal get picked up by the controller when both bogies are in the isolated section, so when the rear of the locomotive gets in the braking zone. This is not ideal when using constant distance braking, as it would mean that a shorter loco will stop before a longer one.

 

Please tell me if my reasoning is flawed.........

 

I think your reasoning is flawed.   It is better to setup the constant braking distance for each loco, and use all the pickups available for reliable running.    So, reconnect the other wheels to give as many wheels as possible picking up power.  

 

The ABC signal (slight voltage drop on one rail) is detected by the decoder in the loco, and that implements the stopping.  

 

 

The problems with stopping distance occur when either a loco is pushing a train (eg. train of coaches with a driving cab in a coach, loco on the rear),  or when there are coaches/wagons which have pickups (eg. lighting) which cross the ABC "gap" and thus reset the braking back to "normal running" as they cross the gap.   
If you have either of these problems, there are solutions, but they require more devices to detect a loco is fully in the braking zone, and then apply the brake zone.  

 

 

- Nigel

 

[vignale]

1 hour ago, Nigelcliffe said:

 

I think your reasoning is flawed.   It is better to setup the constant braking distance for each loco, and use all the pickups available for reliable running. So, reconnect the other wheels to give as many wheels as possible picking up power.  

 

 

- Nigel

 

I feel incredibly silly… of course every locomotive can have its braking distance configured based on its length! It totally makes sense now.

 

As soon as I will have time I will put the required modifications in place and will update the thread.

 

Thank you for your input, it’s been incredibly helpful.

 

Alessandro 

[SRman]

...

6 hours ago, vignale said:

 

I had considered replacing the light bulbs with LEDs, however I find that creating a new solder joint on the old PCB is extremely hard. Solder just doesn’t stick, and this is also why I only connected the new wires where old solder joints were. Any tips for that?

 

Thank for the LED suggestion; I would love to get brighter lights and LEDs are a great way to do it, but also like the warm feeling of incandescent bulbs. Are yours standard white? I can’t seem to find any warm white single LED, they only come in long strips of 5050 bulbs.

 

Thanks again for the lovely feedback,

Alessandro

If the tracks on the PCB are a bit old and tarnished, I polish the bit I want to solder first with a wire brush in my Dremel tool. The flux I use also seems to be quite effective at helping the solder to flow and stick.

The LEDs are standard 5mm white ones. I agree that warm white would be better for older locomotives that in real life used incandescent bulbs. The 5mm LEDs are the most convenient to fit here because they closely mimic the size of the original bulbs. You can see the bluer tint in the photo below.

I actually bought two of these Roco models in the same lot, but one was a much newer model and had a decoder socket on its PCB, with smaller surface mounted LEDs. I didn't really look to see if the light guides remained the same, but thought it safer to use the 5mm LEDs to minimise any disruptions to the alignments.

Edited September 4, 2021 by SRman

[SamThomas]

Yes, connect up both bogies.

 

To improve pickup on OHE/Diesel outline locomotives I replace the traction tyred wheelsets with plain ones. Unless you are pulling in excess of 10 coaches up a helix they have more than enough traction with plain wheels.

[vignale]

Hi everybody again,

 

sorry for replying so late but I didn't have much time to work on the loco.

 

I found some warm white 5mm LEDs (which come with a resistor already soldered for 12V operation) which fit really well in the previous lamp support. I used some sand paper to make them rough and spread the light more evenly, otherwise the light is only in astraight cone and it would have not diffused well.

Due to the lack of space I couldn't run the new wires for the LEDs below or above the PCB (the casing wouldn't fit), so I recycled an unused path in the PCB. The overhead pickup must be disabled, but I have no plans to use it in the future so I do not think it is a problem.

I also added a small 3D printed platform to prevent the wires from getting stuck in the transmission.

 

For future reference, this is what the wiring looks like.

 

The locomotive looks great with the lights turned on!

 

 

Thanks again to everyone! Your help has been incredibly helpful

 

Cheers,

Alessandro

Edited September 14, 2021 by vignale