Scotsman doesn't move (under DCC control)

[Chrissaf]

I put my Scotsman on the track for the first time in a couple of weeks, and nothing happened. It was running fine before.

Five other locos are operating without incident, so track is fine.

I tried inverting it in a cradle, cleaned the wheels and pick ups, applied power directly and still no reaction.

Put it on the programming track to reset decoder CV8, then reset CV again – no reaction.

Changed the decoder, reset CV – no reaction.

I upgraded RM to 1.69 last week, but I doubt that would have any impact.

What’s the next move, if any?

[pidder]

Wonder if you have a blanking plug and could try it on DC just by appplying a 9volt battery to the wheels?

[96RAF]

Try the DC direct rig route as pidder suggests to prove the loco is OK then stick a substitute decoder in to prove the other one is duff.

 

This is where a decoder test rig is handy as you can fiddle with the decoder away from the loco to prove one or tother is the problem.

Rob

[2e0dtoeric]

Is this a TTS Scottie (what's the R number) or a full-blown expensive decoder version?

There has been a bad batch of TTS decoders released which seem to work for a bit, then expire, or only work in one direction - often backwards.

Hornby have been replacing duff ones with no question - contact Admin Adam.

[Fishmanoz]

Sorry to be a pain and reading your post Norman (unlike some others) but I can see that you’ve already swapped decoder to eliminate that and have applied power direct to the wheels.  I suspect you have something simple like a broken wire or maybe a bent tender post connector but let’s ask some questions to try to narrow it down, including questions already asked. 

 

Which FS, there are millions of them?

 

If the answer is the DCC Ready Railroad version from the set, then the fingers on the tender post are in play. What happens when you try it without tender?

 

When you applied power directly to the wheels, DCC or DC power and with decoder or without and the blanking plug?

[NormanQ4]

@Fishmanoz

Hi Fishy thanks for your response and for actually reading my post.

It’s a little disappointing when you take the time to document an issue as best you can and then people don’t read it properly.

I actually posted in General Discussion but SoT and an “unidentified” Mod or Admin decided that it should be listed in the DCC forum and so it was moved.

I posted a couple of lines politely pointing out that I didn’t think that my issue would be exclusive to DCC, but that comment was ignored and deleted.

Your comments regarding a broken wire or dodgy tender post certainly support my belief.

I know the Mods and Admin generally do a very good job but I think sometimes that they may get a little over exuberant in their decision making and by moving my post would have eliminated my exposure to advice from non-DCC users who don't read the DCC forum.

 

Anyway, to get back to giving you more information.

The FS is not from a set but is a DCC Ready Railroad R3086.

Most testing has been done without the tender or the body shell attached.

The initial testing of power directly to the wheels was done with DCC and a selection of different decoders in place which had worked ok in other locos.

I have just inserted a blanking plug and applied a 9 volt battery to the wheels and still no reaction.

I’ve gently disturbed the wiring and see no signs of a breakage.

[96RAF]

Apologies for not spotting that you had changed and reset the decoder.

No I didn’t move your post.

A problem I have had on a Merchant Navy with constant stopping and starting is the pickups on one side under the main driver wheels cover is electrically connected to a brass tab connected through the chassis block by a peg then from the chassis block to the decoder socket. The other side is wired direct from the pickup to the socket. This peg touch-contact has been nothing but trouble so I now plan to replace the whole loco pickups with ESU carriage lighting pickups instead. This may be the same problem on your Scottie.

Rob

[NormanQ4]

@RAF96

Hi Rob, I didn't look under the driver wheel cover, I'll do that now.

[NormanQ4]

@RAF96

It looks ok under the cover plate.

[2e0dtoeric]

Can you spin the motor with a finger? (testing for a jammed mechanism)

Try unplugging the decoder, then connect your PP3 battery directly to the motor brushes. See if the motor runs then.

If it does, follow one side at a time back to the decoder socket, and try the PP3 there.

If t works with the battery connected to the socket, the fault has to be between the wheels and the socket.

[NormanQ4]

@2e0dtoeric

Hi eric, motor spins freely and wheels also turn.

I was just going to add this to my posts when I saw your questions.

I don't have visible brushes.

[96RAF]

Service sheet 380 covers this model which has loco pickups only so disregard the tender which has a fixed drawbar.

 

The characteristics of the worm drive on the motor should stop you turning the wheels and hence the motor. I am a bit confused as you say the motor turns and the wheels turn. If you mean the wheels turn when hand moved then there is a fault in the geartrain. If the motor spins but the wheels do not turn as a result of the motor then this again points at the gear-train.

 

The service sheet should help ID said gear-train parts, but I would suspect a split intermediate gear (items 7) turning with the motor but not torquing the wheels or the gear on the main driver wheel shaft may be split (not drawn on the service sheet).

 

Rob

[NormanQ4]

@RAF96

When the motor is hand turned the wheels also turn albeit at a much slower speed due to gearing.

[Fishmanoz]

By process of elimination you seem to be moving towards it being the motor.  Do you have a multimeter?  If so, check the motor on resistance/ohms range across the motor connections, decoder removed to see if you get a low reading or open circuit. 

[2e0dtoeric]

Norman put - I don't have visible brushes.

They will be inside the motor body, but there should be two wires leading to them. They will be soldered or plugged in to the ends of them, and that is where to connect your PP3 to.

(There may only be one wire, if the loco chassis is 'hard-connected' to the motor - and that could be why the decoder went phut! See all the write-ups about converting Ringfield motors to DCC).

[NormanQ4]

@Fishmanoz

The reading constantly jumps about between 20 and around 70.

@2e0dtoeric

When the PP3 was connected to the motor terminals there was no reaction.

The decoder didn't go phut, all three decoders that were tried still function in other locos.

[96RAF]

Word of warning - NEVER connect DC to the motor terminals if there is a decoder in circuit or it will go phutt.

Rob

[Fishmanoz]

Norman, as far as I can see, you haven’t used invisible ink on your posts, but some are sure still having trouble reading them!!!  Or it might be a case of less red, more read. 

[NormanQ4]

@RAF96

Word of warning - NEVER connect DC to the motor terminals if there is a decoder in circuit or it will go phutt.

 

Fortunately I followed Fishies guidance and removed the decoder prior to testing.  But can someone explain in simple terms why a 9 volt battery would do that.

 

@Fishmanoz

It does get a little frustrating, but when you're desperate for answers you can become very tolerant. 😆

[96RAF]

@norman

Re your geartrain - I was trying to find out if you could turn the wheels by hand as opposed to via the motor, as this would indicate a loose - usually split - gear. The worm acts as an anti-back.

 

This is the best I can do for the decoder to illustrate why ...

...the H-bridge that drives the motor is one way with regard to voltage. Normal flow is top left to bottom right or top right to bottom left. Applying a battery which has a hi-current capacity to the motor terminals would push reverse voltage against the top left or top right component and when out of spec for the device would destroy it or the upstream components.

Note also where an external stay-alive connects.

 

/media/tinymce_upload/4a37eaa12e6089cae9aa174607ed7bcb.jpg

Photo cropped from the internet.

 

Rob

[NormanQ4]

@RAF96

The wheels can't be turned directly by hand.

With regard to the decoder, I won't pretend that I fully understand, but I do get the gist, and that's enough for me not to do it.

[2e0dtoeric]

Note - I did say remove the decoder first, bottom of page 1 - Try unplugging the decoder, then connect your PP3 battery directly to the motor brushes

[NormanQ4]

I apologise Eric, I thought that I had acknowledged that in my reply to your post.

Quite a lot of info happening, I guess I just lost the plot for a bit. 😳

[96RAF]

I guess I just lost the plot for a bit

Plot Losters is a very select club. Applications to join our expanding group are always welcome along with a twenty pound note (Non refundable).

 

Not being able to turn the wheels by hand says the gear train is OK so its back to the motor as prime suspect.

Rob

[peter _murray]

I also had this issue but it turned out to be of my own making. When I fitted the DCC chip I removed what appeared to be a capacitor. The result was no action from the locomotive. When I refitted this component all operated as per expectations.