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Your Layout and Models => Train Surgery => Topic started by: daversmth on July 03, 2017, 03:53:00 pm

Title: Help please for poor running
Post by: daversmth on July 03, 2017, 03:53:00 pm
Hi All,

I have two multiple units that are exhibiting the same bad behaviour. One is a Farish DMU101 371-511, and the other  Farish  EMU 4CEP 372-675. Both were bought as used on ebay, and have had little use. Both have  Bachmann 36-558A DCC decoders fitted ( I fitted them after purchase ). I have a large momentum value set for slow speed ramp up.  Both worked perfectly for quite some while. But now both are exhibiting the same unwanted behaviour where, when DCC ramps up the power to the motor, the train does not move, and after a few seconds the 1.5A current limiter of the control is triggered. So it seems like something is jammed up and causing the motor to draw a lot of current. I see the same behaviour with both the dmu and the emu.

I stripped down the emu completely, could not see anything broken or dirty, reassembled it, but with no change in behaviour as a result.

I reprogrammed the decoder, during which process the train lurched forward slightly in small steps as the instructions were written to it.
This seemed to free the movement and the unit worked for a short while before failing again with the same problem.

I tried both the dmu and emu on DC, and they both run fine.

After a lot of experimentation, suspecting that a "sudden kick" will get the motor to start but a slow ramp up will not, I have managed to get both units running with DCC, with a low value of momentum to get a rapid ramp up of power applied to the motor.

The DMU runs perfectly with this set up unless I run at too high a speed in which case it again causes a 1.5A cut out on the controller.

The EMU still sometimes sticks on startup but will run if left for 20 or 30 seconds.

Has anyone seen similar issues or  have any advice how to "properly" resolve these problems.

I am happy to completely replace all the innards of both units if that is what is required as the bodies are perfect.
If this is needed, could anyone advise what I would need to order to do so ?
Or is there some other solution related to decoder set up or a maintenance issue of the motor/gears etc ?

Thanks in advance

Dave


Title: Re: Help please for poor running
Post by: ntpntpntp on July 03, 2017, 05:25:05 pm
When you say "ran ok on DC" do you mean with the decoder still fitted or with it removed and replaced with a blanking plate (I'm assuming these are plug-in decoders?)

To me it sounds a bit like could be split gears.   Can you hear any sort of clicking sound?
Title: Re: Help please for poor running
Post by: daversmth on July 03, 2017, 06:26:06 pm
Hi,
Thanks for the reply.
When I say ran in DC I meant with the decoder replaced by a blanking plate.
There is no undue noise when the units are running.
Title: Re: Help please for poor running
Post by: Malc on July 03, 2017, 08:32:43 pm
I believe there is a CV that sets the start current. It may need adjusting to give a bit of a kick.
Title: Re: Help please for poor running
Post by: daversmth on July 03, 2017, 08:43:31 pm
Thanks for that.
I see that CV 65 is kickstart.
I will look into it.
Title: Re: Help please for poor running
Post by: daversmth on July 03, 2017, 08:55:20 pm
CV 65 is not supported on the 36-558a decoder but I have other types fitted to other locos so will try to find one that supports it.
Title: Re: Help please for poor running
Post by: PLD on July 04, 2017, 07:37:20 pm
I tried both the dmu and emu on DC, and they both run fine.
When I say ran in DC I meant with the decoder replaced by a blanking plate.
There is no undue noise when the units are running.
That strongly indicates there is no mechanical issue with the units (motor fault, bearings, split gear etc); which points towards something electrical. It could be the chips, it could be the controller or it could be the wiring in between... have you tried any other DCC fitted locos on the same track & controller? If so, how did they perform?? If they also performed badly I'd be suspecting the controller, if they are OK, it suggests the chips in these two units.
Title: Re: Help please for poor running
Post by: daversmth on July 04, 2017, 08:16:16 pm
Thanks for the reply, other dcc locos run fine on the layout.  My suspicion is that Dcc control is more sensitive to a  mechanical problem than DC control. I have exhausted my attempts to find any fault and am beyond my frustration endurance level so will pack them off to a repairer now if I can find one.
Title: Re: Help please for poor running
Post by: RailGooner on July 04, 2017, 08:47:42 pm
If loco 'L1' fitted with DCC chip 'C1' performs poorly and loco 'L2' fitted with chip 'C2' performs without error, what is the result of swapping the chips between the locos? How does loco 'L1' perform when fitted with chip 'C2' and how does loco 'L2' perform when fitted with chip 'C1'?

Basically, does the problem running follow the chip or stay with the loco?
Title: Re: Help please for poor running
Post by: daversmth on July 04, 2017, 08:59:41 pm
Thanks for that. I have a new decoder arriving in a couple of days for a new loco so I will try it in these 2 units first to see what hapoens.
Title: Re: Help please for poor running
Post by: lil chris on July 04, 2017, 10:30:23 pm
I have gf class 108 two car unit,  I fitted a better chip in the powercar( DZ125) and just used one of those gf 36-558 in the trailer car for the lights.
Title: Re: Help please for poor running
Post by: amsie on July 05, 2017, 02:13:22 am
Good advice by Chris.

I had no end of problems with the Hornby VEP using cheapo Bachmann decoders.  By chance I put a Loksound decoder into the VEP and it ran like a dream.  Perhaps a better decoder will give you the faultless running you require.
Title: Re: Help please for poor running
Post by: daversmth on July 05, 2017, 09:41:28 am
Thanks once more for the advice. I will try a different decoder when it arrives.
Title: Re: Help please for poor running
Post by: daversmth on July 06, 2017, 04:25:04 pm
So I tried a different decoder and I still see the same behaviour.
The EMU, for example, either refuses to run at all and triggering the controller current limit cut out when I try to start it, or if it runs, it will suddenly stop after a while, again triggering the controller cut out.
It seems to me that something mechanical is jamming.
I have completely disassembled everything once but could see nothing obvious.
Tempted to do the same again but without knowing what everything should look like when "normal" it is hard to know what the problem is.
Title: Re: Help please for poor running
Post by: austinbob on July 06, 2017, 04:35:40 pm
As PLD stated earlier in the thread its unlikely the problem is mechanical if all is ok on DC. BUT..is all really ok on DC, have you measured the current required to start the loco up. Should only be a few 10's of milliamps. If much more than this there may well be something a bit stiff or something wrong with the motor...
 :beers:
Title: Re: Help please for poor running
Post by: Dr Al on July 06, 2017, 04:46:07 pm
Agree with Austinbob - check current on DC.

4-CEP at full speed should draw absolutely no more than 75-100mA, and likely less, and the DMU likewise (same drive, same motor). Some 4-CEPs have had motors fail, and the first symptoms of this would be high current draw.

Cheers,
Alan

Title: Re: Help please for poor running
Post by: daversmth on July 06, 2017, 05:01:32 pm
Thanks again for the response.
On DC, The EMU will start to run at slow speed drawing 40mA, which I am guessing sounds reasonable.
I only have a short DC test track so cannot really run the EMU for a prolonged period at higher speed to see if anything locks up.
But running the unit back and forth on a short track it never seems to jam up when operated on DC.
On DC, It runs very quiet, with no odd noises, it starts smoothly with no jerking and will run happily at low speed.
So as far as I can tell DC operation seems perfect.
Title: Re: Help please for poor running
Post by: daversmth on July 06, 2017, 05:06:00 pm
I will add that as I slowly ramp the dc voltage to the track, current increases to just under 40mA before the EMU moves. Below that it draws current but does not move.
Title: Re: Help please for poor running
Post by: Dr Al on July 06, 2017, 05:06:31 pm
Sounds fairly healthy. By elimination therefore, it's either something very wrong with the decoder, DCC controller, or configuration of one or other. Definitely reset the decoders before trying again using on DCC to know you're definitely starting from a nominally standard set of setting - usually this is via setting CV8 to a given value dependent on decoder manufacturer - easy to find what to set it to on Google.

Cheers,
Alan
Title: Re: Help please for poor running
Post by: Only Me on July 06, 2017, 05:52:46 pm
Whats your dcc controller.... dont say a hornby select or ez!!?!

If its an ez the adaptor is most likely a 16v one which is ok for OO but bad for N....
Title: Re: Help please for poor running
Post by: austinbob on July 06, 2017, 05:56:21 pm
But the OP says all other locos work fine so maybe not a controller issue. Definitely an odd one this!!!
 :beers:
Title: Re: Help please for poor running
Post by: daversmth on July 06, 2017, 06:44:18 pm
So, having ran the EMU up and down my 1m dc test track for a while trying unsuccessfully to get it to misbehave, I swapped back the dc blanking plug for my dcc decoder, put it back on the dcc track and it has been running perfectly for the last hour on dcc, no matter what I do with it.

The dmu was not moving at all on dcc, I tried the same process of running it on the dc track, and it too now works perfectly on dcc.

I had ran both previously on dc and swapped them back to dcc and dcc misbehaviour was intermittant.

Perhaps badly seated decoder contacts? Or just the mecanical act of man handling during swapping the decoders disturbed something ?  Still not 100% convinced the problems wont reoccur but so far so good.

I cannot see why running the units on DC would cure anything per say so I suspect some side effect my be the reason.
Title: Re: Help please for poor running
Post by: austinbob on July 06, 2017, 06:50:50 pm
Dodgy contacts could be the problem. Maybe plugging the decoder in and out a few times might clean the plug an socket  contacts. However I'd hate for you to do this and find that what's running now stops working.
Decisions, Decisions.
 :hmmm:
Title: Re: Help please for poor running
Post by: daversmth on July 07, 2017, 08:54:13 am
Having run the units for a little while now on DCC the problem has once more returned as bad as ever. I am all out of ideas now.
Title: Re: Help please for poor running
Post by: austinbob on July 07, 2017, 09:00:01 am
Having run the units for a little while now on DCC the problem has once more returned as bad as ever. I am all out of ideas now.
You've probably tried all this already but maybe double check:
Are the decoder contacts and sockets clean. Are they loose causing intermittent contact.
Check the soldered connections to the decoder sockets, any dry joints need careful resoldering.
Check for strands of wire from one decoder socket contact to another which may intermittently cause a short.
Check the wires for similar solder and wire strands at the other end also.
Finally if all is ok but fault is still there, Nip down the pub for a pint and wait for another Forum suggestion (of the helpful kind of course)
Sorry you're having all this trouble. These niggly faults can be very frustrating.
Good Luck
 :beers: :beers:
Title: Re: Help please for poor running
Post by: Only Me on July 07, 2017, 09:21:03 am
Hiya, take the motor out and clean out the gap between the commutator poles, i suspect they have become clogged which will cause all sorts of issues as the motor heats up including high current draw
Title: Re: Help please for poor running
Post by: daversmth on July 07, 2017, 09:24:07 am
Thanks all once more for all your help.
I have decided to pack them up and send them  off to Bachmann service department.
And a note to all - current charge is 22.50 with the first 7.50 of parts free.
It goes up to 30.00 in August.
Title: Re: Help please for poor running
Post by: Only Me on July 07, 2017, 10:44:37 am
I do repairs for future reference 😉
Title: Re: Help please for poor running
Post by: PLD on July 07, 2017, 01:29:04 pm
Thanks all once more for all your help.
I have decided to pack them up and send them  off to Bachmann service department.
And a note to all - current charge is 22.50 with the first 7.50 of parts free.
It goes up to 30.00 in August.
Make sure you include a covering note stating they run fine on DC but not on DCC, otherwise what Bachmann will do is just test them on DC (as you have done) and find nothing wrong (as you did) and return to you as "nothing abnormal detected"...

From all you have told us about how the performance differs on DC V DCC and deteriorates with running on DCC, does point towards a poor/intermittent connection in the DCC circuitry whether that is a poorly fitting chip/socket or another loose connection somewhere on the PCB...
Title: Re: Help please for poor running
Post by: daversmth on July 07, 2017, 03:50:36 pm
I did include a description of the fault when I sent them off - thanks for the suggestion anyway.
To be frank, given the intermittent and convoluted nature of the fault I am not expecting them to come back any better than they went, but having spent hours on the problem could not spend any more time myself. Will have to sell on as spares or repair if there is no improvement.
When the frustration level gets this bad the hobby no longer becomes a pleasure.
Given that it is likely that issues will arise with other locos from time to time I was hoping to be able to learn how to do my own repairs, but when I have completely stripped everything down and can see nothing wrong there was no more I could do.
It does seem odd, though, that I have two units that exhibit the behaviour, but have not seen any reports of the same behaviour elsewhere.

In the meantime I will content myself with what runs - I now have 8 different trains running all at the same time on my 6' x 3' layout, under computer control from a JMRI script that I have written. Choo chooooo, as my wife says every time she passes by ....


Title: Re: Help please for poor running
Post by: austinbob on July 07, 2017, 03:55:14 pm
At least you've still got trains to enjoy. Good luck with the repairs.
 :beers:
Title: Re: Help please for poor running
Post by: daversmth on July 11, 2017, 05:17:32 pm
Just to complete the post - Bachmann replaced the motors in both units. Not got them back yet but assume thats case closed.
Title: Re: Help please for poor running
Post by: Newportnobby on July 11, 2017, 05:28:29 pm
When you get them back let us know how they run, please, Dave.
Title: Re: Help please for poor running
Post by: daversmth on July 16, 2017, 11:19:29 am
So far the emu and 101 multiple units that had the motors replaced are running fine.

I did also send a third unit ( a DMU 108 ) not previously mentioned in this post, which was totally dead.
They replaced the PCB - it ran for about 2 minutes but has now stopped responding again - so I will return it for further investigation.
I can use DCC to turn the lights on and off but it does not respond to throttle settings.
Title: Re: Help please for poor running
Post by: daversmth on April 14, 2018, 10:22:31 am
Just an update on this topic.
I have now had 4 out of my 13 motors that have had to be replaced within 12 months, one for a new loco under warranty.

Given the frequency at which this occurs, the last time it happened I decided it was worthwhile seeing if I could do the motor replacement myself. So I purchased a replacement motor from BR lines and did the deed myself. That loco now runs fine and not too difficult to do if you take your time and make a careful mental note how it all fits together as you take it apart. I had to strip and reassamble twice but got there second time around.
I find most issues with my locos are resolved by cleaning wheel pickups or pcb to motor contacts. (They are all dcc) but sometimes motor replacement is needed.
15  a time to fix the issue is a lot more reasonable than the cost of sending it for repair.
I have been surprised though at how often the little blighters seem to need repair or maintenance.
Title: Re: Help please for poor running
Post by: Bealman on April 14, 2018, 10:34:20 am
It seems to be a worrying trend which is, once again worrying, cropping up frequently on the forum.
Title: Re: Help please for poor running
Post by: NinOz on April 14, 2018, 10:47:19 am
I have now had 4 out of my 13 motors that have had to be replaced within 12 months, one for a new loco under warranty.
Is there any pattern to the running time for each motor replacement or just random?
Title: Re: Help please for poor running
Post by: daversmth on April 14, 2018, 09:07:45 pm
I have now had 4 out of my 13 motors that have had to be replaced within 12 months, one for a new loco under warranty.
Is there any pattern to the running time for each motor replacement or just random?
Random I would say. The motor fault seems to manifest in the same way though with the motor running a short while then tripping the current limiter on the controller.
Title: Re: Help please for poor running
Post by: PLD on April 15, 2018, 12:02:03 am
Just an update on this topic.
I have now had 4 out of my 13 motors that have had to be replaced within 12 months, one for a new loco under warranty.
I have to say that is an exceptionally high attrition rate, and so unless you consider yourself extremely unlucky, we have to consider whether there is another common causal factor unique to your set-up... What controller(s) are you using? what is the input power supply (volts and amps), what is the output when not under load??

It seems to be a worrying trend which is, once again worrying, cropping up frequently on the forum.
BUT like most of these recurring issues isolated to a small minority of users and not affecting the majority...
 :hmmm:
Title: Re: Help please for poor running
Post by: daversmth on April 15, 2018, 07:27:36 am
Just an update on this topic.
I have now had 4 out of my 13 motors that have had to be replaced within 12 months, one for a new loco under warranty.
I have to say that is an exceptionally high attrition rate, and so unless you consider yourself extremely unlucky, we have to consider whether there is another common causal factor unique to your set-up... What controller(s) are you using? what is the input power supply (volts and amps), what is the output when not under load??

It seems to be a worrying trend which is, once again worrying, cropping up frequently on the forum.
BUT like most of these recurring issues isolated to a small minority of users and not affecting the majority...
 :hmmm:

Thanks for the input.
I had the same thought about an underlying cause but have looked into that and came up with a blank.
I will just have to see how it goes from here and hope that the pattern does not continue.

Title: Re: Help please for poor running
Post by: Bramshot on April 15, 2018, 11:09:49 am
I also have had at least one motor burn out, mine was a Class 55, and it took the decoder chip with it. It was the same decoder you were originally using. The Bachmann one with the blue heat shrink?

The new Bachmann Decoder is somewhat better IMO, gives very smooth low speed response BUT the connection pins are made from very soft copper and are not of a sufficiently heavy gauge to make good contact with the sockets. They drift in and out of the socket with very little force and I think would fall out out if held at the wrong angle. I have to put a kink in the pins to get a good grip and contact.

I have told Bachmann about this and they say they are looking into it.

These decoders are Zimo, by the way.
Title: Re: Help please for poor running
Post by: daversmth on October 23, 2018, 08:56:49 am
So it's been a while but I have another failed motor.
At least I have now learnt how to replace them myself rather than send them away for repair which saves a lot of money.


With regard to further investigation, I am going to find out how to reduce the current limit of 1.5A on my controller to a lower value so that if a high current load is demanded of it by an errant motor, it will be less likely to cause damage.

I was also wondering if, when a loco stutters, on a turnout for example, does the back emf setting in the decoder cause the decoder to demand a high current from the controller, which then causes a problem when the loco reconnects with the track after the turnout, the demand causing a high curent to kick in until it settles again.
Title: Re: Help please for poor running
Post by: Dr Al on October 24, 2018, 09:28:01 am
To be honest, you are unlikely to be able to cut the current limit to a level that will truly protect any motor - these will die at as low as 300mA - they run on very little (sub 50mA). They simply overheat and melt and destroy the commutator. Also, if you limit the current too much you'll risk tripping things when running multiple trains or double heading etc.

Bear in mind this may just be a usage failure - these motors don't have a huge lifespan (some say as little as 100hrs). I've replaced a few now.

On DCC - one thing that should be turned off or minimised is any feedback (which I presume is your 'back emf' setting) or suchlike - this will drive motors harder and as generally not recommended in N on DC or DCC precisely because the motors are pretty delicate.

Cheers,
Alan
Title: Re: Help please for poor running
Post by: daversmth on October 24, 2018, 10:05:45 am
 Thank you for your advice. Very useful.